physicsworld--2020-09-15--Will AI bots ever replace science journalists? (And no, this was written by a human) - Physics World

I ’ m not a machine ( as far as I ’ m aware ) but one day AI bots will probably replace at least some aspects of my job as a science journalist .
Still , could these computer systems ever really be capable of doing “ proper ” science journalism ?
And what is science journalism anyway ?
These were some of the questions at the heart of a session on AI journalism at the European Conference of Science Journalism ( ECSJ ) , which took place on 1 September in Trieste , Italy , with most participants @ @ @ @ @ @ @ this technology in a way that ’ s helpful for us , I think it can help science journalism , enrich it and make our jobs easier , ” said Mićo Tatalović , news editor of Research Fortnight .
Tatalović pointed to several examples where AI has already entered the newsroom and other forms of science communication .
They include ( e ) Science News , a website that employs an AI editor to curate its news across a range of disciplines .
Elsewhere , there ’ s Science Surveyor , which can @ @ @ @ @ @ @ and SciNote , which can help you write your next scientific paper .
Tatalović spent a year working with computer scientists at Massachusetts Institute of Technology developing an AI bot to automate science news-writing .
The group trained a neural network to write jargon-free text by feeding it with news articles from Science Daily along with the corresponding research papers behind the stories .
Tatalović believes that the system would become increasingly skilled with additional data .
So could such systems eventually remove the need for science reporters like me ?
Not likely @ @ @ @ @ @ @ from Cardiff University , another speaker on the ECSF panel .
“ There is a carapace of public descriptions of what AI can do , which doesn ’ t necessarily reflect what AI really can actually do.
” A case in point was the Guardian ’ s op-ed last week with the somewhat misleading headline “ A robot wrote this entire article .
Are you scared yet , human ?
“ , which was produced by the GPT-3 language generator .
A note following the reasonably well-written piece revealed that editors had cherrypicked @ @ @ @ @ @ @ different essays – giving readers an exaggerated view of GPT-3 ’ s capabilities .
Interested in the sociological dimensions of big-science projects , Collins spent over four decades following the quest to directly detect gravitational waves .
He believes the real key to that historic first detection in 2015 was human interaction , underlining that the LIGO-Virgo collaboration had previously rejected several apparent detections .
“ The real art of science is working out what ’ s good data and what ’ s rubbish , ” he said .
Collins argued that if @ @ @ @ @ @ @ science , then by extension the same is true for science journalism .
“ Serious journalism is where people are trying to get themselves to the frontier of science and develop a real serious understanding of science , ” he said .
You can see the full discussion in this video , also featuring Fabiana Zollo from Ca ’ Foscari University of Venice and Charlie Beckett of the London School of Economics .

Friend or foe: AI bots could assist or replace science journalists (Courtesy: iStock/sompong_tom)
I’m not a machine (as far as I’m aware) but one day AI bots will probably replace at least some aspects of my job as a science journalist. Still, could these computer systems ever really be capable of doing “proper” science journalism? And what is science journalism anyway?
These were some of the questions at the heart of a session on AI journalism at the European Conference of Science Journalism (ECSJ), which took place on 1 September in Trieste, Italy, with most participants joining remotely.
“If we deploy this technology in a way that’s helpful for us, I think it can help science journalism, enrich it and make our jobs easier,” said Mićo Tatalović, news editor of Research Fortnight. Tatalović pointed to several examples where AI has already entered the newsroom and other forms of science communication.
They include (e) Science News, a website that employs an AI editor to curate its news across a range of disciplines. Elsewhere, there’s Science Surveyor, which can provide background information to a field, and SciNote, which can help you write your next scientific paper.
Tatalović spent a year working with computer scientists at Massachusetts Institute of Technology developing an AI bot to automate science news-writing. The group trained a neural network to write jargon-free text by feeding it with news articles from Science Daily along with the corresponding research papers behind the stories. Tatalović believes that the system would become increasingly skilled with additional data.
So could such systems eventually remove the need for science reporters like me?
Not likely, said Harry Collins, a sociologist from Cardiff University, another speaker on the ECSF panel. “There is a carapace of public descriptions of what AI can do, which doesn’t necessarily reflect what AI really can actually do.”
A case in point was the Guardian’s op-ed last week with the somewhat misleading headline “A robot wrote this entire article. Are you scared yet, human?“, which was produced by the GPT-3 language generator. A note following the reasonably well-written piece revealed that editors had cherrypicked and edited the best bits from eight different essays – giving readers an exaggerated view of GPT-3’s capabilities.
Interested in the sociological dimensions of big-science projects, Collins spent over four decades following the quest to directly detect gravitational waves. He believes the real key to that historic first detection in 2015 was human interaction, underlining that the LIGO-Virgo collaboration had previously rejected several apparent detections. “The real art of science is working out what’s good data and what’s rubbish,” he said.
Collins argued that if AI is of limited use in breakthrough science, then by extension the same is true for science journalism. “Serious journalism is where people are trying to get themselves to the frontier of science and develop a real serious understanding of science,” he said.
You can see the full discussion in this video, also featuring Fabiana Zollo from Ca’ Foscari University of Venice and Charlie Beckett of the London School of Economics.


physicsworld--2020-09-18--Astronomers plan huge neutrino observatory in the Pacific Ocean - Physics World

Astrophysicists in Germany and North America have published plans to build the world ’ s largest neutrino telescope on the sea floor off the coast of Canada .
The Pacific Ocean Neutrino Experiment ( P-ONE ) is designed to snare very-high-energy neutrinos generated by extreme events from beyond our galaxy .
Neutrino telescopes observe the Cerenkov radiation that is emitted when neutrinos passing through the Earth interact very occasionally with atomic nuclei resulting in the production of fast-moving secondary particles .
Being uncharged and exceptionally inert , neutrinos can penetrate gas and dust as they travel through the universe , @ @ @ @ @ @ @ exceptionally energetic phenomena that generate them .
Photons from such events , in contrast , are absorbed on their journey .
The world ’ s largest neutrino telescope , known as IceCube , consists of dozens of strings of photomultiplier tubes suspended in holes drilled deep into the ice at the South Pole .
Covering a volume of 1 km3 , IceCube made history in 2013 when it reported intercepting the first extragalactic neutrinos .
Four years later it then recorded an event that could be tied to a very distant , bright @ @ @ @ @ @ @ thanks to concurrent gamma-ray observations .
According to P-ONE head , Elisa Resconi at the University of Munich , IceCube ’ s 2017 result strictly speaking only constitutes “ evidence ” for the blazar source .
To really claim a discovery and pinpoint the origin of other cosmic neutrinos , she argues , requires the construction of additional neutrino observatories as well as the extension of IceCube .
“ We are now on the verge of opening up neutrino astronomy , ” she says , “ but if we base this process on @ @ @ @ @ @ @ really long time , perhaps decades.
” P-ONE will consist of seven groups of 10 detector strings creating an instrument volume of about 3 km3 .
Being larger than IceCube , it will detect rarer , higher-energy neutrinos , and will be most sensitive at a few tens rather than a handful of teraelectronvolts .
It will also observe a different part of the sky , mainly capturing neutrinos from the southern hemisphere rather than the north .
But there will be some overlap between the two , says Resconi , potentially allowing @ @ @ @ @ @ @ The new facility will be located at a depth of about 2.6 km in the Cascadia Basin , some 200 km from the coast of British Columbia .
As such , it will take advantage of pre-existing infrastructure – an 800 km-long loop of fibre-optic cable operated by the University of Victoria ’ s Ocean Networks Canada that supplies power and ferries data to and from existing sea-floor instruments .
Having already confirmed that this site has the necessary optical properties by sending down two initial strings of light emitters and sensors in @ @ @ @ @ @ @ planning to deploy a steel cable with additional detectors to investigate the site – including spectrometers , lidars and a muon detector .
The plan then , says Resconi , is to install the first part of the observatory – a ring containing seven 1 km-long strings – around the end of 2023 .
And if that succeeds , the researchers will then apply for the bulk of the $ 50–100m needed to complete the project , with personnel costs adding roughly $ 100m more .
Resconi hopes that the full observatory will @ @ @ @ @ @ @ end of the decade .
But she describes this timeline as “ very ambitious ” .
In addition to delays caused by the ongoing COVID- 19 pandemic , she says it will be a challenge to ensure that the detectors work as planned – given the huge pressures and the presence of salt and sea creatures , which together make the seabed such a harsh environment .
IceCube identifies four galaxies as likely sources of cosmic rays Indeed , scientists had already planned on operating a cubic-kilometre scale neutrino telescope known as KM @ @ @ @ @ @ @ Sea back in 2014 , which was delayed to 2020 .
According to collaboration member Feifei Huang , just two of the 230 strings due to be installed off the coast of southern Italy are so far in place , while another site in French waters currently has six out of a planned 115 strings running – with completion not foreseen until 2026 and 2024 respectively .
Resconi says that part of the problem with that project is a lack of specialist personnel , with the physicists essentially doing everything themselves – for @ @ @ @ @ @ @ which connect cables on the sea floor , having failed .
She hopes that the experience acquired by Ocean Networks Canada will mean a similar fate can be avoided for P-ONE .
With 30 or 40 people dedicated to laying cables in the ocean , she says that her team “ can focus on the physics ” .

Ocean bound: P-ONE will consist of seven groups of 10 detector strings, creating an instrument larger than the existing IceCube experiment (pictured). (Courtesy: IceCube Collaboration/NSF)
Astrophysicists in Germany and North America have published plans to build the world’s largest neutrino telescope on the sea floor off the coast of Canada. The Pacific Ocean Neutrino Experiment (P-ONE) is designed to snare very-high-energy neutrinos generated by extreme events from beyond our galaxy.
Neutrino telescopes observe the Cerenkov radiation that is emitted when neutrinos passing through the Earth interact very occasionally with atomic nuclei resulting in the production of fast-moving secondary particles. Being uncharged and exceptionally inert, neutrinos can penetrate gas and dust as they travel through the universe, allowing astronomers in principle to identify the exceptionally energetic phenomena that generate them. Photons from such events, in contrast, are absorbed on their journey.
We are now on the verge of opening up neutrino astronomy Elisa Resconi
The world’s largest neutrino telescope, known as IceCube, consists of dozens of strings of photomultiplier tubes suspended in holes drilled deep into the ice at the South Pole. Covering a volume of 1 km3, IceCube made history in 2013 when it reported intercepting the first extragalactic neutrinos. Four years later it then recorded an event that could be tied to a very distant, bright galactic nucleus known as a blazar, thanks to concurrent gamma-ray observations.
According to P-ONE head, Elisa Resconi at the University of Munich, IceCube’s 2017 result strictly speaking only constitutes “evidence” for the blazar source. To really claim a discovery and pinpoint the origin of other cosmic neutrinos, she argues, requires the construction of additional neutrino observatories as well as the extension of IceCube. “We are now on the verge of opening up neutrino astronomy,” she says, “but if we base this process on just one telescope it could take a really long time, perhaps decades.”
Heading underwater
P-ONE will consist of seven groups of 10 detector strings creating an instrument volume of about 3 km3. Being larger than IceCube, it will detect rarer, higher-energy neutrinos, and will be most sensitive at a few tens rather than a handful of teraelectronvolts. It will also observe a different part of the sky, mainly capturing neutrinos from the southern hemisphere rather than the north. But there will be some overlap between the two, says Resconi, potentially allowing independent observations of the same event.
The new facility will be located at a depth of about 2.6 km in the Cascadia Basin, some 200 km from the coast of British Columbia. As such, it will take advantage of pre-existing infrastructure – an 800 km-long loop of fibre-optic cable operated by the University of Victoria’s Ocean Networks Canada that supplies power and ferries data to and from existing sea-floor instruments.
Having already confirmed that this site has the necessary optical properties by sending down two initial strings of light emitters and sensors in 2018, the P-ONE collaboration are now planning to deploy a steel cable with additional detectors to investigate the site – including spectrometers, lidars and a muon detector. The plan then, says Resconi, is to install the first part of the observatory – a ring containing seven 1 km-long strings – around the end of 2023. And if that succeeds, the researchers will then apply for the bulk of the $50–100m needed to complete the project, with personnel costs adding roughly $100m more.
Resconi hopes that the full observatory will be installed and taking data by the end of the decade. But she describes this timeline as “very ambitious”. In addition to delays caused by the ongoing COVID- 19 pandemic, she says it will be a challenge to ensure that the detectors work as planned – given the huge pressures and the presence of salt and sea creatures, which together make the seabed such a harsh environment. Read more Looking at the sky from under water
Indeed, scientists had already planned on operating a cubic-kilometre scale neutrino telescope known as KM 3 NeT on the floor of the Mediterranean Sea back in 2014, which was delayed to 2020. According to collaboration member Feifei Huang, just two of the 230 strings due to be installed off the coast of southern Italy are so far in place, while another site in French waters currently has six out of a planned 115 strings running – with completion not foreseen until 2026 and 2024 respectively.
Resconi says that part of the problem with that project is a lack of specialist personnel, with the physicists essentially doing everything themselves – for example, their self-built junction boxes, which connect cables on the sea floor, having failed. She hopes that the experience acquired by Ocean Networks Canada will mean a similar fate can be avoided for P-ONE. With 30 or 40 people dedicated to laying cables in the ocean, she says that her team “can focus on the physics”.


physicsworld--2020-09-18--Floating oil droplet contains hundreds of degenerate optical modes - Physics World

Microscopic oil droplets held aloft with optical tweezers can contain more than 200 resonant optical modes of similar energies , creating “ hyperdegeneracy ” for the first time .
That is the claim of researchers in Israel , Spain and the US , who say that their breakthrough could ultimately find application in high-speed optical communications , sensing , quantum data processing and even the creation of dynamic optical circuits .
When optical materials with a high refractive index are formed into certain symmetrical shapes — such as rings , cylinders or spheres —light can be repeatedly reflected around the @ @ @ @ @ @ @ the same way that sound waves pass around the inside edge of St Paul ’ s Cathedral ’ s famous “ whispering gallery ” .
The circulating light undergoes constructive interference , forming discrete resonant modes – or so-called degenerate states – with similar energies .
The number of modes is dependent on the ratio between the light ’ s wavelength and the circumference of the resonator — meaning that , in theory , a spherical object with a circumference tens of microns in size could support hundreds of modes of either visible @ @ @ @ @ @ @ however , achieving such hyperdegeneracy has proven impossible with conventional fabrication techniques .
This is because even a single stem supporting the sphere will reduce the object ’ s symmetry and thereby reduce the extent of the potential degeneracy .
In a new study , however , mechanical engineer Tal Carmon of the Technion-Israel Institute of Technology and his colleagues have circumvented this issue by supporting a 10 micron spherical droplet of silicone oil within an optical tweezer , thereby removing the need for a disruptive structural support .
In fact , the @ @ @ @ @ @ @ to almost completely preserve the spherical symmetry of the oil droplet – along with the potential for hyperdegeneracy .
In addition , the researchers explain , the levitation keeps the surface of the microresonator clean and unscratched .
Writing in the journal Physical Review X , they say “ unlike solids , the liquid droplet does not contain any dislocation , inclinations , and thermally induced stresses , which are typical for solid resonators and reduce their quality ” .
To reveal the modes , the team placed a tapered fibre close to @ @ @ @ @ @ @ passed near-infrared laser light into and out of the droplet by means of an evanescent coupling .
In the resulting transmission spectrum , the team observed signals of more than 200 modes – the largest-recorded set of degenerate states to ever be measured .
The modes did exhibit slight differences in energy ; this was a product of the droplet not being perfectly spherical , but distorted slightly as a result of the pressure from the optical tweezers , the presence of the coupled fibre , and the effect of gravity .
The @ @ @ @ @ @ @ write Peking University physicists Qi-Tao Cao and Yun-Feng Xiao in a commentary on the Physical Review X paper .
“ As a mesoscopic analogue to a single atom , levitated microresonators could serve as well-controlled platforms for simulating atomic optics , ” they explain .
Other potential applications could lie in using single-photon versions of the resonators as qubits for quantum processing , the creation of malleable circuits using multiple droplets , and high-capacity optical communications through the use of different modes to form densely packed information channels .
Cao and Xiao also @ @ @ @ @ @ @ used in existing sensing applications .
“ The frequency of hyperdegenerate modes is extremely sensitive to external perturbation , and even a tiny [ such disturbance ] – such as a biomolecule near the resonator surface — could lead to measurable modulation [ of the light modes ] ” .
Dmitry Skryabin at the University of Bath adds , “ The extremely high degeneracy and ability to manipulate it for fundamental studies of many coupled oscillators in linear , nonlinear and quantum regimes links these results to many cross-area ideas ” .
“ @ @ @ @ @ @ @ also link to the cross-disciplinary concept of Arnold tongues and oscillator synchronization in the context of frequency comb research .
”

Floating in space: microscope image of a suspended oil droplet with the tapered fibre out-of-focus in the background. (Courtesy: Jacob Kher-Alden et al./Physical Review X)
Microscopic oil droplets held aloft with optical tweezers can contain more than 200 resonant optical modes of similar energies, creating “hyperdegeneracy” for the first time. That is the claim of researchers in Israel, Spain and the US, who say that their breakthrough could ultimately find application in high-speed optical communications, sensing, quantum data processing and even the creation of dynamic optical circuits.
When optical materials with a high refractive index are formed into certain symmetrical shapes — such as rings, cylinders or spheres —light can be repeatedly reflected around the inside of the material, much in the same way that sound waves pass around the inside edge of St Paul’s Cathedral’s famous “whispering gallery”. The circulating light undergoes constructive interference, forming discrete resonant modes – or so-called degenerate states – with similar energies.
The number of modes is dependent on the ratio between the light’s wavelength and the circumference of the resonator — meaning that, in theory, a spherical object with a circumference tens of microns in size could support hundreds of modes of either visible or near-infrared light. In practice, however, achieving such hyperdegeneracy has proven impossible with conventional fabrication techniques. This is because even a single stem supporting the sphere will reduce the object’s symmetry and thereby reduce the extent of the potential degeneracy.
Clean and unscratched
In a new study, however, mechanical engineer Tal Carmon of the Technion-Israel Institute of Technology and his colleagues have circumvented this issue by supporting a 10 micron spherical droplet of silicone oil within an optical tweezer, thereby removing the need for a disruptive structural support. In fact, the radiation pressure from the laser-based tweezers acts to almost completely preserve the spherical symmetry of the oil droplet – along with the potential for hyperdegeneracy. In addition, the researchers explain, the levitation keeps the surface of the microresonator clean and unscratched.
Writing in the journal Physical Review X ,they say “unlike solids, the liquid droplet does not contain any dislocation, inclinations, and thermally induced stresses, which are typical for solid resonators and reduce their quality”.
To reveal the modes, the team placed a tapered fibre close to the surface of the oil microsphere and passed near-infrared laser light into and out of the droplet by means of an evanescent coupling. In the resulting transmission spectrum, the team observed signals of more than 200 modes – the largest-recorded set of degenerate states to ever be measured. The modes did exhibit slight differences in energy; this was a product of the droplet not being perfectly spherical, but distorted slightly as a result of the pressure from the optical tweezers, the presence of the coupled fibre, and the effect of gravity.
Simulating atomic optics
The technology could have several practical applications, write Peking University physicists Qi-Tao Cao and Yun-Feng Xiao in a commentary on the Physical Review X paper. “As a mesoscopic analogue to a single atom, levitated microresonators could serve as well-controlled platforms for simulating atomic optics,” they explain. Other potential applications could lie in using single-photon versions of the resonators as qubits for quantum processing, the creation of malleable circuits using multiple droplets, and high-capacity optical communications through the use of different modes to form densely packed information channels.
Cao and Xiao also point out that the microspheres could be used in existing sensing applications. “The frequency of hyperdegenerate modes is extremely sensitive to external perturbation, and even a tiny [such disturbance] – such as a biomolecule near the resonator surface — could lead to measurable modulation [of the light modes]”.
Dmitry Skryabin at the University of Bath adds, “The extremely high degeneracy and ability to manipulate it for fundamental studies of many coupled oscillators in linear, nonlinear and quantum regimes links these results to many cross-area ideas”. “Ultra-high finesses and near degeneracies in resonators also link to the cross-disciplinary concept of Arnold tongues and oscillator synchronization in the context of frequency comb research.”


physicsworld--2020-09-18--Microswimmers benefit from thermoelectric guidance - Physics World

Microscopic devices made from so-called Janus particles can be made to “ swim ” through liquid with the help of light-induced thermoelectric fields .
The devices , which can travel 100μm along a straight course in 39 seconds , might find applications in biomedical sensing and the targeted , non-invasive delivery of drugs , according to developers at the University of Texas at Austin , US .
Janus particles – named for the famously two-faced Roman god of beginnings and transitions – are tiny spheres coated with different materials on each side .
With the right choice of coatings , @ @ @ @ @ @ @ ” , travelling in a specific direction when placed in a chemical solution and driven by light , magnetic , electric or ultrasonic fields .
Light-driven microswimmers are particularly promising for applications inside the body , as they can be controlled remotely with high spatial and temporal resolution .
Their chief drawback is that their direction of travel becomes increasingly erratic over time thanks to rotational Brownian motion – the random motion of particles suspended in a medium .
In designing their microswimmers , Yuebing Zheng and colleagues found a way of overcoming @ @ @ @ @ @ @ microswimmers by covering a glass substrate with a single layer of pristine polystyrene beads using a technique called spin coating .
They then used physical vapour deposition to cover one side of the beads with a gold film .
The resulting Janus particles were freely dispersed in an aqueous solution containing a cation surfactant called CTAC .
This surfactant makes the beads positively charged , while also introducing spherical fatty molecules , or micelles , of CTAC into the solution along with Cl– ions .
While the gold sides of the Janus particles @ @ @ @ @ @ @ , the uncoated sides do not .
The temperature gradient thus produced redistributes the CTAC micelles and Cl– ions , causing an electric field to build up around the charged particles .
According to Zhihan Chen , the study ’ s co-first author , this opto-thermoelectric force plays a key role in determining the particle ’ s behaviour .
When the researchers illuminated the particles with de-focused laser light , the particles swam in the direction of the optothermally-generated light fields .
When they switched to a focused laser beam , however , @ @ @ @ @ @ @ of linear travel and rotations is similar to the “ run-and-tumble ” motion of swimming microorganisms such as E. Coli bacteria , and it can be maintained thanks to the balance between the opto-thermoelectric , optical and Stokes drag forces .
To keep their Janus particles moving in the right direction , Zheng and colleagues developed a feedback control algorithm to switch between the particles ’ swimming and rotating states .
By carefully observing the particles in real time , the researchers were able to adjust their control algorithm to make it automatically @ @ @ @ @ @ @ from the desired path .
Once the particles realign , the algorithm re-activates their swimming state .
Through repeated switching between states , the researchers showed that they could make the Janus particles travel in a straight line – behaviour that could be exploited for non-invasive drug delivery in the body , Chen says .
The researchers , who report their work in Light : Science & Applications , now plan to improve the navigation efficiency of their microbots .
“ In our present study , we showed that 5-μm microswimmers can directionally @ @ @ @ @ @ @ , but we would like to double this figure and deliver the particles over the same distance in just 18 seconds , ” Chen says .
“ We could achieve this by further improving the response time of our imaging camera and laser shutters.
” The team also plan to further develop their control algorithm so it can steer multiple particles at the same time , while also adding non-collision and path optimization functions .
The half-gold , half-uncoated Janus particles studied in this work are a common type , but in the @ @ @ @ @ @ @ functionalize their polystyrene beads by loading macromolecules onto their uncoated surfaces .
“ This strategy would enable efficient and targeted cargo delivery totally driven by light , ” Chen tells Physics World .

Under light fields, polystyrene/gold Janus particles are set to swim and rotate alternatively such that they follow a predefined path (reprinted under Creative Commons Attribution 4.0 International License)
Microscopic devices made from so-called Janus particles can be made to “swim” through liquid with the help of light-induced thermoelectric fields. The devices, which can travel 100μm along a straight course in 39 seconds, might find applications in biomedical sensing and the targeted, non-invasive delivery of drugs, according to developers at the University of Texas at Austin, US.
Janus particles – named for the famously two-faced Roman god of beginnings and transitions – are tiny spheres coated with different materials on each side. With the right choice of coatings, such particles will act as “microswimmers”, travelling in a specific direction when placed in a chemical solution and driven by light, magnetic, electric or ultrasonic fields.
Light-driven microswimmers are particularly promising for applications inside the body, as they can be controlled remotely with high spatial and temporal resolution. Their chief drawback is that their direction of travel becomes increasingly erratic over time thanks to rotational Brownian motion – the random motion of particles suspended in a medium.
Asymmetric photothermal response
In designing their microswimmers, Yuebing Zheng and colleagues found a way of overcoming this problem. The researchers made the microswimmers by covering a glass substrate with a single layer of pristine polystyrene beads using a technique called spin coating. They then used physical vapour deposition to cover one side of the beads with a gold film. The resulting Janus particles were freely dispersed in an aqueous solution containing a cation surfactant called CTAC. This surfactant makes the beads positively charged, while also introducing spherical fatty molecules, or micelles, of CTAC into the solution along with Cl– ions.
While the gold sides of the Janus particles heat up when illuminated with laser light, the uncoated sides do not. The temperature gradient thus produced redistributes the CTAC micelles and Cl– ions, causing an electric field to build up around the charged particles. According to Zhihan Chen, the study’s co-first author, this opto-thermoelectric force plays a key role in determining the particle’s behaviour.
Comparison with swimming microorganisms
When the researchers illuminated the particles with de-focused laser light, the particles swam in the direction of the optothermally-generated light fields. When they switched to a focused laser beam, however, the particles rotated in-plane. The combination of linear travel and rotations is similar to the “run-and-tumble” motion of swimming microorganisms such as E. Coli bacteria, and it can be maintained thanks to the balance between the opto-thermoelectric, optical and Stokes drag forces.
To keep their Janus particles moving in the right direction, Zheng and colleagues developed a feedback control algorithm to switch between the particles’ swimming and rotating states. By carefully observing the particles in real time, the researchers were able to adjust their control algorithm to make it automatically set the particles rotating whenever they deviate from the desired path. Once the particles realign, the algorithm re-activates their swimming state. Through repeated switching between states, the researchers showed that they could make the Janus particles travel in a straight line – behaviour that could be exploited for non-invasive drug delivery in the body, Chen says.
Improving navigation efficiency
The researchers, who report their work in Light: Science & Applications, now plan to improve the navigation efficiency of their microbots. “In our present study, we showed that 5-μm microswimmers can directionally transport over 110 μm in 39 seconds, but we would like to double this figure and deliver the particles over the same distance in just 18 seconds,” Chen says. “We could achieve this by further improving the response time of our imaging camera and laser shutters.”
The team also plan to further develop their control algorithm so it can steer multiple particles at the same time, while also adding non-collision and path optimization functions.
The half-gold, half-uncoated Janus particles studied in this work are a common type, but in the future, Zheng and colleagues hope to functionalize their polystyrene beads by loading macromolecules onto their uncoated surfaces. “This strategy would enable efficient and targeted cargo delivery totally driven by light,” Chen tells Physics World.


physicsworld--2020-09-18--Curved toes point to sore feet, the chaos of the knuckleball - Physics World

Most conventional running shoes have a “ toe spring ” – a gentle upward curve of the sole towards the tip of the shoe .
While this makes stepping more comfortable and easier , Harvard University ’ s Daniel Lieberman , Oliver Hansen and Nicholas Holowka have found that a toe spring can weaken the foot ’ s ability to push off the ground .
This , they say , could be associated with a range of foot problems including plantar fasciitis – a painful condition affecting the tissue that connects the heel to the toes .
“ We think @ @ @ @ @ @ @ relying on their plantar fascia to do what muscles normally do , ” explains Lieberman .
“ When you get weak muscles and the plantar fascia has to do more work , it ’ s not really evolved for that , and so it gets inflamed.
” In their experiment , 13 participants walked barefoot and in four pairs of custom-made sandals on a treadmill equipped with force plates and an infrared camera system .
You can read more about the team ’ s research in “ Your shoes were made for walking @ @ @ @ @ @ @ ” .
“ The knuckleball is perhaps the most enigmatic pitch in baseball , ” is the opening line of the abstract of a paper by Nicholas Nelson and Eric Strauss at California State University in Chico .
The knuckleball pitch involves the slow rotation of the ball as it speeds towards the batter .
Because a baseball has prominent seams that disrupt airflow around the ball , the aerodynamics of the ball changes as it rotates , which causes its trajectory to change repeatedly during flight .
This makes it very difficult @ @ @ @ @ @ @ of the ball and hit it effectively .
Conversely , it is also a very difficult pitch to throw because tiny changes in technique can have huge effects on outcome .
Indeed , some pitchers say that identically thrown knuckleballs can take very different trajectories .
In their paper , Nelson and Strauss develop a model of the knuckleball and show the motion of the ball is chaotic .
The duo ’ s model predicts that the position of the ball when it reaches the batter can vary by as much as 1.2 @ @ @ @ @ @ @ knuckleball pitchers .
This variation can take the ball well outside the strike zone ( where the pitch must be ) , which illustrates why the knuckleball can be a dangerous choice for a pitcher .
You can read more in their paper “ Dynamical chaos in a simple model of a knuckleball ” .

Toe curling: the toe spring makes it easier to step, but could also be damaging feet. (Courtesy: Harvard University)
Most conventional running shoes have a “toe spring” – a gentle upward curve of the sole towards the tip of the shoe. While this makes stepping more comfortable and easier, Harvard University’s Daniel Lieberman, Oliver Hansen, Freddy Sichting and Nicholas Holowka have found that a toe spring can weaken the foot’s ability to push off the ground. This, they say, could be associated with a range of foot problems including plantar fasciitis – a painful condition affecting the tissue that connects the heel to the toes.
“We think that what happens is that people are relying on their plantar fascia to do what muscles normally do,” explains Lieberman. “When you get weak muscles and the plantar fascia has to do more work, it’s not really evolved for that, and so it gets inflamed.”
In their experiment, 13 participants walked barefoot and in four pairs of custom-made sandals on a treadmill equipped with force plates and an infrared camera system. You can read more about the team’s research in “Your shoes were made for walking. And that may be the problem”.
Enigmatic pitch
“The knuckleball is perhaps the most enigmatic pitch in baseball,” is the opening line of the abstract of a paper by Nicholas Nelson and Eric Strauss at California State University in Chico. The knuckleball pitch involves the slow rotation of the ball as it speeds towards the batter. Because a baseball has prominent seams that disrupt airflow around the ball, the aerodynamics of the ball changes as it rotates, which causes its trajectory to change repeatedly during flight. This makes it very difficult for the batter to anticipate the motion of the ball and hit it effectively. Conversely, it is also a very difficult pitch to throw because tiny changes in technique can have huge effects on outcome. Indeed, some pitchers say that identically thrown knuckleballs can take very different trajectories.
In their paper, Nelson and Strauss develop a model of the knuckleball and show the motion of the ball is chaotic. The duo’s model predicts that the position of the ball when it reaches the batter can vary by as much as 1.2 m for typical initial conditions used by knuckleball pitchers. This variation can take the ball well outside the strike zone (where the pitch must be), which illustrates why the knuckleball can be a dangerous choice for a pitcher.
You can read more in their paper “Dynamical chaos in a simple model of a knuckleball”.


physicsworld--2020-09-18--Build a bot: new book covers history and future of robotics - Physics World

They grow up so fast .
It seems like only yesterday that the cherubic little darling was gazing wide-eyed at the world , waving its arms incoherently as it figured out how to move .
Now it reaches out with those pudgy little arms , purposefully picking up toys and stacking them on top of each other as it actively plays .
However , this change didn ’ t happen over months , or weeks , or even since “ only yesterday ” – it ’ s been mere hours .
The reason is that this is not a child @ @ @ @ @ @ @ one-metre tall robot built by researchers at the Italian Institute of Technology in Genova that is designed to resemble a small child , as well as learn like one .
The robotic youngster starts out only able to move its eyes , learning to focus on objects of interest .
As time progresses , skills develop and motor restrictions are unlocked , to simulate muscle development , and iCub learns to point , play with toys and even use objects as crude tools to push buttons .
iCub was developed to explore the @ @ @ @ @ @ @ the notion that the development of human-like cognition is dependent on learning to physically interact one ’ s environment – and that , by extension , the development of a truly human-like artificial intelligence is dependent on it having a physical body .
The rationale for the hypothesis is at the heart of computer scientist Mark Lee of the University of Aberystwyth ’ s new book , How to Grow a Robot : Developing Human-Friendly , Social AI .
The first third of Lee ’ s work explores the history of and current @ @ @ @ @ @ @ AI ) – from pallet-carrying bots in warehouses to computer chess champions – and highlights the issues that arise from trying to derive generalized AI from the prevailing task-based approach to developing AI .
The middle section moves on to how robots like iCub might be taught to grow and learn through developmental interactions with their surroundings .
The final section speculates on the future of robotics , considering where and how fast AI might develop and touching on topics including the risk of the singularity , a concern that Lee emphatically dismisses @ @ @ @ @ @ @ more could easily have been made out of them .
It was also a pity to see trans-humanism defined reductively as being solely about “ downloading the brain ” .
It strikes me that less extreme concepts , such as technological augmentation to expand the limits of the human body could have been explored in a book that examines how we are in many ways defined by the nature and extent of our embodiment .
Overall , How to Grow a Robot is a rich and comprehensive introduction to robotics and artificial intelligence @ @ @ @ @ @ @ its heart .
However , it has one central flaw – in my opinion , it is sadly not a sufficiently engaging read .
Both of Lee ’ s previous books – on intelligent robotics and assembly systems , respectively – appear to have been intended for a specifically academic readership , rather than the popular audience that this book is marketed at .
Perhaps Lee , like many scientists before him , found it a challenge to reshape his material for non-specialists .
Yes , the explanations are largely there – and @ @ @ @ @ @ @ fact boxes ( although I still remain none-the-wiser as to Lee ’ s distinction between consciousness and self-awareness ) .
However , the work has the feel of a “ recommended class reading ” , down to the end-chapter bullet lists repeating key “ take-aways ” for the reader .
Personally , I prefer my casual non-fiction to not be presented as if there might be a pop quiz on the material later .
More images of some of the commercial robots described in the opening chapter would also have been welcome for @ @ @ @ @ @ @ by their absence .
Other structural aspects , meanwhile , serve to bring to mind a different academic format : that of a dissertation or thesis .
On the positive side , the work has one well-explained central argument around which the whole book is constructed – a strength some of its popular-science peers could stand to learn from .
Unfortunately , this is countered by repeated instances where the author sets up an interesting area of exploration before punting it to a reference text .
The clichéd academic phrase “ beyond the @ @ @ @ @ @ @ not used , but it might as well have been – variations on “ we do not have the space ” recur in its place , and create the looming impression of some word limit narrowly met and avenues curtailed .
Taking time to direct the reader to extraneous material is admirable , but such links belong in footnotes , not as disruptions to the main text that leave the average reader feeling underserved – especially if they do not have access to the kind of academic library that would be needed to @ @ @ @ @ @ @ short , How to Grow a Robot is a detailed and informative read – but one whose style and framing might better recommend it to a computer science syllabus rather than your coffee table .

Physics World. Members of the Institute of Physics can enjoy the full issue Taken from the September 2020 issue of. Members of the Institute of Physics can enjoy the full issue via the Physics World app
Ian Randall reviews How to Grow a Robot: Developing Human-Friendly, Social AI by Mark Lee
Skills study The childlike iCub is a robot designed to explore whether human-like cognition is predicated on having a physical body. (Courtesy: Massimo Brega, The Lighthouse/Science Photo Library)
They grow up so fast. It seems like only yesterday that the cherubic little darling was gazing wide-eyed at the world, waving its arms incoherently as it figured out how to move. Now it reaches out with those pudgy little arms, purposefully picking up toys and stacking them on top of each other as it actively plays. However, this change didn’t happen over months, or weeks, or even since “only yesterday” – it’s been mere hours. The reason is that this is not a child, but iCub, a wide-eyed, one-metre tall robot built by researchers at the Italian Institute of Technology in Genova that is designed to resemble a small child, as well as learn like one.
The robotic youngster starts out only able to move its eyes, learning to focus on objects of interest. As time progresses, skills develop and motor restrictions are unlocked, to simulate muscle development, and iCub learns to point, play with toys and even use objects as crude tools to push buttons.
iCub was developed to explore the so-called “embodied cognition hypothesis”, the notion that the development of human-like cognition is dependent on learning to physically interact one’s environment – and that, by extension, the development of a truly human-like artificial intelligence is dependent on it having a physical body. The rationale for the hypothesis is at the heart of computer scientist Mark Lee of the University of Aberystwyth’s new book, How to Grow a Robot: Developing Human-Friendly, Social AI.
The first third of Lee’s work explores the history of and current developments in robotics and artificial intelligence (AI) – from pallet-carrying bots in warehouses to computer chess champions – and highlights the issues that arise from trying to derive generalized AI from the prevailing task-based approach to developing AI. The middle section moves on to how robots like iCub might be taught to grow and learn through developmental interactions with their surroundings.
The final section speculates on the future of robotics, considering where and how fast AI might develop and touching on topics including the risk of the singularity, a concern that Lee emphatically dismisses. These areas are rich enough that more could easily have been made out of them. It was also a pity to see trans-humanism defined reductively as being solely about “downloading the brain”. It strikes me that less extreme concepts, such as technological augmentation to expand the limits of the human body could have been explored in a book that examines how we are in many ways defined by the nature and extent of our embodiment.
Back to the future Mark Lee’s new book spans pallet-carrying bots and the potential for transhumanism. (Courtesy: iStock/Ekkasit919)
Overall, How to Grow a Robot is a rich and comprehensive introduction to robotics and artificial intelligence, with a very clear message at its heart. However, it has one central flaw – in my opinion, it is sadly not a sufficiently engaging read.
Both of Lee’s previous books – on intelligent robotics and assembly systems, respectively – appear to have been intended for a specifically academic readership, rather than the popular audience that this book is marketed at. Perhaps Lee, like many scientists before him, found it a challenge to reshape his material for non-specialists. Yes, the explanations are largely there – and I appreciated the use of periodic jargon-busting fact boxes (although I still remain none-the-wiser as to Lee’s distinction between consciousness and self-awareness). However, the work has the feel of a “recommended class reading”, down to the end-chapter bullet lists repeating key “take-aways” for the reader. Personally, I prefer my casual non-fiction to not be presented as if there might be a pop quiz on the material later. More images of some of the commercial robots described in the opening chapter would also have been welcome for the general reader, and were conspicuous by their absence.
Personally, I prefer my casual non-fiction to not be presented as if there might be a pop quiz on the material later
Other structural aspects, meanwhile, serve to bring to mind a different academic format: that of a dissertation or thesis. On the positive side, the work has one well-explained central argument around which the whole book is constructed – a strength some of its popular-science peers could stand to learn from. Unfortunately, this is countered by repeated instances where the author sets up an interesting area of exploration before punting it to a reference text. The clichéd academic phrase “beyond the scope of the present work” is not used, but it might as well have been – variations on “we do not have the space” recur in its place, and create the looming impression of some word limit narrowly met and avenues curtailed. Taking time to direct the reader to extraneous material is admirable, but such links belong in footnotes, not as disruptions to the main text that leave the average reader feeling underserved – especially if they do not have access to the kind of academic library that would be needed to follow up on such references.
In short, How to Grow a Robot is a detailed and informative read – but one whose style and framing might better recommend it to a computer science syllabus rather than your coffee table.
2020 MIT Press 384pp £22.50hb


physicsworld--2020-09-17--Evidence for life is found on Venus, wider access to the best radiotherapy - Physics World

In this episode the astronomy writer Keith Cooper is on hand to chat about the surprising discovery of phosphine in @ @ @ @ @ He explains that here on Earth , microbial life is the only natural source of @ @ @ @ @ that life exists in the clouds of Venus .
Cooper also speculates about how future @ @ @ @ @ zone ” of the Venusian atmosphere could search for life .
Today , there is @ @ @ @ @ care across the world with people living in low- and middle-income countries having limited access @ @ @ @ @ .
This imbalance is the focus of the social enterprise company EmpowerRT , which was @ @ @ @ @ North Carolina medical physicist Sha Chang .
In this episode , Chang and her colleague @ @ @ @ @ World ’ s Tami Freeman about what can be done to provider greater access to @ @ @ @

In this episode the astronomy writer Keith Cooper is on hand to chat about the surprising discovery of phosphine in the atmosphere of Venus. He explains that here on Earth, microbial life is the only natural source of phosphine – which could mean that life exists in the clouds of Venus. Cooper also speculates about how future missions to the “habitable zone” of the Venusian atmosphere could search for life.
Today, there is a huge disparity in cancer care across the world with people living in low- and middle-income countries having limited access to the best radiotherapy treatments. This imbalance is the focus of the social enterprise company EmpowerRT, which was founded by the University of North Carolina medical physicist Sha Chang. In this episode, Chang and her colleague Cielle Collins talk to Physics World’s Tami Freeman about what can be done to provider greater access to the best treatments.


physicsworld--2020-09-19--CERN’s emissions equal to a large cruise liner, says report - Physics World

Greenhouse-gas emissions emitted by the CERN particle-physics lab near Geneva in 2018 were 223 800 tonnes of carbon-dioxide equivalent – similar to the emissions from a large cruise liner .
That is according to the lab ’ s first public Environment Report that details the status of CERN ’ s environmental footprint and outlines some objectives to reduce it in the coming years .
The report finds that three quarters of these emissions came from the fluorinated gases used for particle detection and cooling of the particle detectors .
Covering the years 2017 and 2018 , the report underlines the @ @ @ @ @ @ @ to reduce its emissions .
“ It has provoked debate and increased the environmental awareness of all the people who work here as well as our user community , and made us think hard about what we do now and how we design the next generation of accelerators , ” says Frédérick Bordry , CERN director for accelerators and technology .
The report covers everything from noise and biodiversity to water use and radiation .
Comparing all these aspects , reducing the use of fluorinated gases will have the greatest positive impact and @ @ @ @ @ @ @ do this such as repairing gas leaks in the LHC , optimizing gas re-circulation systems .
The ultimate goal is to replace fluorinated gases in the detector cooling systems with carbon dioxide , whose global warming potential is a few thousand times lower .
“ When we built the Large Hadron Collider we didn ’ t appreciate the global-warming potential of these gases ; our main concern was the ozone hole , ” says Bordry .
The facility has set itself an objective of reducing its direct greenhouse gas emissions by 28 % @ @ @ @ @ @ @ by example : going green in the lab The report also sets out plans for tackling CERN ’ s indirect greenhouse emissions – those due to its small-city-sized appetite for electricity .
“ We are implementing energy-recovery systems at the LHC , and pioneering the use of superconductivity on a large scale , which could improve the efficiency of electricity distribution networks , ” says Bordry .
But until the LHC ’ s successor arrives – maybe in the 2040s or 2050s – there is a limit to how much CERN can reduce @ @ @ @ @ @ @ whether probing the mysteries of the universe can justify such significant greenhouse emissions .
“ It ’ s really positive that CERN staff are being transparent about their impacts and that they have set themselves an absolute reduction in emissions target , as opposed to a greenwash-style intensity metric , ” says John Barrett , from the Sustainability Research Institute at the University of Leeds .
“ The advancement of scientific understanding is clearly important and you don ’ t get much bigger than CERN .
Personally , I would prefer to spend @ @ @ @ @ @ @ high-impact flights for a drunken weekend in Prague .
”

Counting the cost: Water vapour rises from cooling towers for the ATLAS detector – part of the energy bill for CERN outlined in the lab’s first environmental report (Courtesy: CERN/Maximilien Brice)
Greenhouse-gas emissions emitted by the CERN particle-physics lab near Geneva in 2018 were 223 800 tonnes of carbon-dioxide equivalent – similar to the emissions from a large cruise liner. That is according to the lab’s first public Environment Report that details the status of CERN’s environmental footprint and outlines some objectives to reduce it in the coming years. The report finds that three quarters of these emissions came from the fluorinated gases used for particle detection and cooling of the particle detectors.
Covering the years 2017 and 2018, the report underlines the scale of the challenge that CERN faces to reduce its emissions. “It has provoked debate and increased the environmental awareness of all the people who work here as well as our user community, and made us think hard about what we do now and how we design the next generation of accelerators,” says Frédérick Bordry, CERN director for accelerators and technology.
It’s really positive that CERN staff are being transparent about their impacts and that they have set themselves an absolute reduction in emissions target, as opposed to a greenwash-style intensity metric John Barrett
The report covers everything from noise and biodiversity to water use and radiation. Comparing all these aspects, reducing the use of fluorinated gases will have the greatest positive impact and the report sets out a path to do this such as repairing gas leaks in the LHC, optimizing gas re-circulation systems. The ultimate goal is to replace fluorinated gases in the detector cooling systems with carbon dioxide, whose global warming potential is a few thousand times lower. “When we built the Large Hadron Collider we didn’t appreciate the global-warming potential of these gases; our main concern was the ozone hole,” says Bordry. The facility has set itself an objective of reducing its direct greenhouse gas emissions by 28% by the end of 2024.
The report also sets out plans for tackling CERN’s indirect greenhouse emissions – those due to its small-city-sized appetite for electricity. “We are implementing energy-recovery systems at the LHC, and pioneering the use of superconductivity on a large scale, which could improve the efficiency of electricity distribution networks,” says Bordry. But until the LHC’s successor arrives – maybe in the 2040s or 2050s – there is a limit to how much CERN can reduce its environmental footprint and some will question whether probing the mysteries of the universe can justify such significant greenhouse emissions.
“It’s really positive that CERN staff are being transparent about their impacts and that they have set themselves an absolute reduction in emissions target, as opposed to a greenwash-style intensity metric,” says John Barrett, from the Sustainability Research Institute at the University of Leeds. “The advancement of scientific understanding is clearly important and you don’t get much bigger than CERN. Personally, I would prefer to spend our carbon budget on CERN than short high-impact flights for a drunken weekend in Prague.”


physicsworld--2020-09-21--CityU physics: where regional connections  underpin global research ambitions - Physics World

Ambition , agility , connection , diversity : it ’ s uncanny how often these themes are echoed and amplified in conversations with faculty in the City University of Hong Kong ’ s Department of Physics .
As such , the sense of shared and collective endeavour is hard to miss among senior CityU physics scholars and early-career scientists , all seemingly pulling in the same direction .
Their goal is certainly ambitious – to create one of the leading centres of excellence for physics research and education in the Asia-Pacific region – and doubly so for a department that @ @ @ @ @ @ @ after CityU chose to create distinct disciplinary specialisms from the former combined physics and materials science programme .
Fast forward to the turbulent here and now – navigating the perfect storm of the coronavirus pandemic against a backdrop of ongoing political tension in Hong Kong – and it ’ s clear that ambition alone will not suffice if CityU ’ s Department of Physics is to sustain its fast-track growth trajectory .
The development roadmap is certainly non-trivial , with a target of around 30 physics faculty members on board by 2027 ( @ @ @ @ @ @ @ ) .
It ’ s also the intention that postgraduate numbers , currently at 79 , will scale significantly over the same timeframe to around 150 PhD students , while the number of postdoctoral researchers and research assistants , currently 30 , is forecast to triple by 2027 .
With the world in flux , agile thinking and adaptive execution look like the “ new normal ” for organizations big and small , whether academic , governmental or corporate .
Just as well that those attributes are reflected in the start-up mindset at @ @ @ @ @ @ @ an ability to pivot at pace unlike some of the bigger , more established physics programmes in Asia and further afield .
A case in point is CityU ’ s Science Summer Camp .
This high-profile event , which was held back in July , seeks to woo outstanding prospective PhD candidates as they embark on their postgraduate studies within physics and other core research disciplines .
In normal times , the Summer Camp would see international students attend a five-day programme of seminars , meetings and laboratory visits across the CityU campus @ @ @ @ @ @ @ however , and faced with ongoing Covid travel restrictions , CityU management successfully transformed the 2020 event into a two-day online meeting that engaged a diverse cohort of 40 students , all of them able to join safely from their homes in mainland China , Australia , Bangladesh , India , Vietnam , the US and Hong Kong .
Beyond that , CityU Department of Physics appears open to further experimentation , flexing and aligning its approach to postgraduate recruitment to address the unprecedented uncertainty facing research students globally .
Witness CityU ’ @ @ @ @ @ @ @ candidates starting their research studies this autumn , opportunistically targeting graduates from Hong Kong and mainland China who are no longer able ( or willing ) to study in Europe or North America owing to the pandemic restrictions .
It helps , of course , that CityU was ranked number one in terms of “ International Outlook ” in the Times Higher Education World University Rankings for 2020 .
“ Nobody knows what the future holds just now , but one thing is certain : Hong Kong will remain a special city with @ @ @ @ @ @ @ east and west , ” explains Xin ( Sunny ) Wang , a CityU theoretical physicist who specializes in fundamental studies of quantum systems and quantum computation .
“ My group and the wider CityU physics programme are at the start of a journey , ” he adds .
“ There are all sorts of exciting research opportunities here – as well as generous funding – for talented physics graduates who can help us to grow our visibility , recognition and impact.
” Sunny Wang exemplifies the relative youth of CityU ’ s @ @ @ @ @ @ @ the academic staff are under 40 .
After graduating from Peking University in 2005 , he spent the next decade working in the US – a PhD at Columbia University in the City of New York followed by postdoctoral studies at the University of Maryland – before returning to CityU as an assistant professor in 2015 ( he was promoted to associate professor earlier this year ) .
“ There ’ s real unity , energy and a spirit of togetherness across the physics faculty , ” he notes .
“ Ultimately that @ @ @ @ @ @ @ that ’ s approachable , accessible and here to help.
” Currently , Sunny Wang supervises a team of six PhD students , four of them drawn from universities in mainland China , one from Malaysia , and the other a local Hong Kong graduate .
In the medium term , though , he hopes to diversify that talent pool , adding one to two graduate students a year , ideally from the near abroad in Asia and perhaps further afield .
“ International collaboration is the engine-room of our future research success @ @ @ @ @ @ @ ’ s a virtuous circle .
We need talented international students coming here to establish their research careers , subsequently reinforcing CityU ’ s reputation with their friends and colleagues as they progress and move on elsewhere.
” For Sunny Wang , those international connections , and the ideas flowing from them , are the lifeblood of his work as a theoretician – and indeed Hong Kong ’ s great strength as a regional research hub .
“ Hong Kong connects east and west at scale , ” he explains .
“ Leading @ @ @ @ @ @ @ through the Territory , sharing their work and their insights – like bees cross-pollinating a field of wild-flowers.
” Connection and diversity are themes endorsed enthusiastically by Shubo Wang who , as head of graduate admissions for CityU Department of Physics , is responsible for building the pipeline of prospective PhD students into the physics programme .
Another faculty member on the right side of 40 , Shubo Wang heads up a team of five PhD students and two research assistants working on theoretical aspects of photonics , including metamaterials , photonic crystals @ @ @ @ @ @ @ is clear , ” he explains .
“ We want to increase the cultural diversity of our PhD students by recruiting graduates with high potential from all over the world , bringing in their unique research experiences , ideas and perspectives.
” Shubo Wang , for his part , reckons the pedigree of CityU ’ s physics faculty , and the staff ’ s extensive international connections , are among the big selling points for would-be PhD students .
Four of the senior team are Fellows of the American Physical Society , while @ @ @ @ @ @ @ top-tier reputations in disciplines as diverse as topological materials , quantum computing , low-dimensional systems and laser spectroscopy .
The generous funding environment also helps , geared towards attracting the best overseas graduate talent to Hong Kong ( see “ CityU physics : PhD applications in brief ” , below ) .
The Hong Kong PhD Fellowship Scheme is a case in point .
This selective programme ( there are around 300 recipients each year ) provides postgraduates with an annual salary of around US $ 40,000 .
That salary is topped up @ @ @ @ @ @ @ work-related travel , with supplements from CityU .
Ultimately , claims Shubo Wang , the strong financial support plus high-class research facilities make Hong Kong a great place for a young physicist to establish their career and forge lasting connections in Asia .
“ Our job at CityU is to help rising stars to shine brighter , ” he concludes .

City University of Hong Kong wants to scale and diversify its PhD physics programme by recruiting a new generation of rising stars from all over the world
Global outlook: Xun-Li Wang (foreground), head of CityU’s Department of Physics, pictured with three of his PhD students at Oak Ridge National Laboratory’s Spallation Neutron Source (SNS) in Tennessee, US. Working with SNS instrumentation scientist Douglas Abernathy (centre) and other international collaborators, the team demonstrated the existence of high-frequency transverse phonons in metallic glass for the first time. (Courtesy: CityU Hong Kong)
Ambition, agility, connection, diversity: it’s uncanny how often these themes are echoed and amplified in conversations with faculty in the City University of Hong Kong’s Department of Physics. As such, the sense of shared and collective endeavour is hard to miss among senior CityU physics scholars and early-career scientists, all seemingly pulling in the same direction. Their goal is certainly ambitious – to create one of the leading centres of excellence for physics research and education in the Asia-Pacific region – and doubly so for a department that only came into being in July 2017 after CityU chose to create distinct disciplinary specialisms from the former combined physics and materials science programme.
Fast forward to the turbulent here and now – navigating the perfect storm of the coronavirus pandemic against a backdrop of ongoing political tension in Hong Kong – and it’s clear that ambition alone will not suffice if CityU’s Department of Physics is to sustain its fast-track growth trajectory. The development roadmap is certainly non-trivial, with a target of around 30 physics faculty members on board by 2027 (versus a current staff cohort of 21). It’s also the intention that postgraduate numbers, currently at 79, will scale significantly over the same timeframe to around 150 PhD students, while the number of postdoctoral researchers and research assistants, currently 30, is forecast to triple by 2027.
Think fast, move faster
With the world in flux, agile thinking and adaptive execution look like the “new normal” for organizations big and small, whether academic, governmental or corporate. Just as well that those attributes are reflected in the start-up mindset at CityU Department of Physics – manifest in an ability to pivot at pace unlike some of the bigger, more established physics programmes in Asia and further afield.
A case in point is CityU’s Science Summer Camp. This high-profile event, which was held back in July, seeks to woo outstanding prospective PhD candidates as they embark on their postgraduate studies within physics and other core research disciplines. In normal times, the Summer Camp would see international students attend a five-day programme of seminars, meetings and laboratory visits across the CityU campus. These are not normal times, however, and faced with ongoing Covid travel restrictions, CityU management successfully transformed the 2020 event into a two-day online meeting that engaged a diverse cohort of 40 students, all of them able to join safely from their homes in mainland China, Australia, Bangladesh, India, Vietnam, the US and Hong Kong.
Sunny Wang: “Hong Kong connects east and west at scale.” (Courtesy: CityU Hong Kong)
Beyond that, CityU Department of Physics appears open to further experimentation, flexing and aligning its approach to postgraduate recruitment to address the unprecedented uncertainty facing research students globally. Witness CityU’s fast-track consideration of prospective physics PhD candidates starting their research studies this autumn, opportunistically targeting graduates from Hong Kong and mainland China who are no longer able (or willing) to study in Europe or North America owing to the pandemic restrictions. It helps, of course, that CityU was ranked number one in terms of “International Outlook” in the Times Higher Education World University Rankings for 2020.
“Nobody knows what the future holds just now, but one thing is certain: Hong Kong will remain a special city with a special role at the nexus between east and west,” explains Xin (Sunny) Wang, a CityU theoretical physicist who specializes in fundamental studies of quantum systems and quantum computation. “My group and the wider CityU physics programme are at the start of a journey,” he adds. “There are all sorts of exciting research opportunities here – as well as generous funding – for talented physics graduates who can help us to grow our visibility, recognition and impact.”
Sunny Wang exemplifies the relative youth of CityU’s physics faculty – around a third of the academic staff are under 40. After graduating from Peking University in 2005, he spent the next decade working in the US – a PhD at Columbia University in the City of New York followed by postdoctoral studies at the University of Maryland – before returning to CityU as an assistant professor in 2015 (he was promoted to associate professor earlier this year). “There’s real unity, energy and a spirit of togetherness across the physics faculty,” he notes. “Ultimately that means students benefit from a staff team that’s approachable, accessible and here to help.”
Currently, Sunny Wang supervises a team of six PhD students, four of them drawn from universities in mainland China, one from Malaysia, and the other a local Hong Kong graduate. In the medium term, though, he hopes to diversify that talent pool, adding one to two graduate students a year, ideally from the near abroad in Asia and perhaps further afield. “International collaboration is the engine-room of our future research success,” he explains. “It’s a virtuous circle. We need talented international students coming here to establish their research careers, subsequently reinforcing CityU’s reputation with their friends and colleagues as they progress and move on elsewhere.”
For Sunny Wang, those international connections, and the ideas flowing from them, are the lifeblood of his work as a theoretician – and indeed Hong Kong’s great strength as a regional research hub. “Hong Kong connects east and west at scale,” he explains. “Leading physicists and early-career researchers come and go through the Territory, sharing their work and their insights – like bees cross-pollinating a field of wild-flowers.”
Wanted: rising stars
Connection and diversity are themes endorsed enthusiastically by Shubo Wang who, as head of graduate admissions for CityU Department of Physics, is responsible for building the pipeline of prospective PhD students into the physics programme. Another faculty member on the right side of 40, Shubo Wang heads up a team of five PhD students and two research assistants working on theoretical aspects of photonics, including metamaterials, photonic crystals and optomechanical systems.
“The priority is clear,” he explains. “We want to increase the cultural diversity of our PhD students by recruiting graduates with high potential from all over the world, bringing in their unique research experiences, ideas and perspectives.”
Shubo Wang: “We want to recruit physics graduates with high potential from all over the world.” (Courtesy: CityU Hong Kong)
Shubo Wang, for his part, reckons the pedigree of CityU’s physics faculty, and the staff’s extensive international connections, are among the big selling points for would-be PhD students. Four of the senior team are Fellows of the American Physical Society, while many younger faculty members have already established top-tier reputations in disciplines as diverse as topological materials, quantum computing, low-dimensional systems and laser spectroscopy.
The generous funding environment also helps, geared towards attracting the best overseas graduate talent to Hong Kong (see “CityU physics: PhD applications in brief”, below). The Hong Kong PhD Fellowship Scheme is a case in point. This selective programme (there are around 300 recipients each year) provides postgraduates with an annual salary of around US$40,000. That salary is topped up with US$1700 a year for work-related travel, with supplements from CityU.
Ultimately, claims Shubo Wang, the strong financial support plus high-class research facilities make Hong Kong a great place for a young physicist to establish their career and forge lasting connections in Asia. “Our job at CityU is to help rising stars to shine brighter,” he concludes.


physicsworld--2020-09-21--Planet-forming disc is torn apart in triple star system - Physics World

The young triple star system GW Orionis appears to be surrounded by a ring of gas and dust that has torn away and become misaligned with the rest of the system ’ s circumstellar disc .
That is the conclusion of an international team of astronomers led by Stefan Kraus at the University of Exeter – who combined observations with numerical simulations to identify disc structures that have been confined to theory until now .
Astronomers believe that most stars are born with one or more companions , which interact in complex ways with the disc of planet-forming gas and @ @ @ @ @ @ @ this disc is misaligned with the orbital planes of the host stars , previous simulations have predicted that it will warp and tear under their gravitational torque , forming distinct rings in separate planes from the rest of the disc .
So far , however , astronomers have yet to identify this tearing in their observations of misaligned discs .
In their study , Kraus ’ team aimed to verify this tearing process by making detailed observations of the triple star system , GW Orionis .
At just around 1 million years old @ @ @ @ @ @ @ has yet to collapse to form planets ; while at its centre , the orbital planes of its three stars are highly misaligned with each other .
Over 11 years beginning in 2008 , the researchers used the Very Large Telescope ( VLT ) and Atacama Large Millimeter Array ( ALMA ) telescopes in Chile to measure thermal emissions and scattered visible light originating from the system .
This allowed them to map the distribution of material in the disc .
The team identified three distinct rings from these measurements ; the outer @ @ @ @ @ @ @ each other , but not with the innermost .
Containing roughly 30 Earth masses of material , this innermost ring is highly misaligned both with the circumstellar disc , and the orbital planes of its three host stars .
This means that the ring casts a shadow on the rest of the disc , allowing the astronomers to define its 3D shape and orientation .
The team followed up these observations with advanced numerical simulations of GW Orionis .
As they hoped , the innermost part the virtual disc warped and tore off @ @ @ @ @ @ @ with the same shape as they had observed .
By tearing material out of the main disc in this way , such a ring could potentially form planets with exotic tilted orbits and long orbital periods ; and which may even travel in the opposite directions to the rotations of their host stars .
These ideas will be explored in more detail through further observations with both the VLT and ALMA , potentially leading to discoveries of newly formed planets within the GW Orionis system .
In turn , theories about such formation @ @ @ @ @ @ @ of exoplanets in binary and tertiary systems .
The research is described in Science .

Torn disc: artist’s impression of the circumstellar disc surrounding GW Orionis. The innermost ring can be seen at an angle to the rest of the disc. (Courtesy: ESO/L Calçada, Exeter/Kraus et al.)
The young triple star system GW Orionis appears to be surrounded by a ring of gas and dust that has torn away and become misaligned with the rest of the system’s circumstellar disc. That is the conclusion of an international team of astronomers led by Stefan Kraus at the University of Exeter – who combined observations with numerical simulations to identify disc structures that have been confined to theory until now.
Astronomers believe that most stars are born with one or more companions, which interact in complex ways with the disc of planet-forming gas and dust surrounding the stellar system. If this disc is misaligned with the orbital planes of the host stars, previous simulations have predicted that it will warp and tear under their gravitational torque, forming distinct rings in separate planes from the rest of the disc. So far, however, astronomers have yet to identify this tearing in their observations of misaligned discs.
In their study, Kraus’ team aimed to verify this tearing process by making detailed observations of the triple star system, GW Orionis. At just around 1 million years old, the system’s circumstellar disc has yet to collapse to form planets; while at its centre, the orbital planes of its three stars are highly misaligned with each other. Over 11 years beginning in 2008, the researchers used the Very Large Telescope (VLT) and Atacama Large Millimeter Array (ALMA) telescopes in Chile to measure thermal emissions and scattered visible light originating from the system. This allowed them to map the distribution of material in the disc.
Casting a shadow
The team identified three distinct rings from these measurements; the outer two of which are closely aligned with each other, but not with the innermost. Containing roughly 30 Earth masses of material, this innermost ring is highly misaligned both with the circumstellar disc, and the orbital planes of its three host stars. This means that the ring casts a shadow on the rest of the disc, allowing the astronomers to define its 3D shape and orientation.
The team followed up these observations with advanced numerical simulations of GW Orionis. As they hoped, the innermost part the virtual disc warped and tore off into a separate, misaligned ring, with the same shape as they had observed. By tearing material out of the main disc in this way, such a ring could potentially form planets with exotic tilted orbits and long orbital periods; and which may even travel in the opposite directions to the rotations of their host stars.
These ideas will be explored in more detail through further observations with both the VLT and ALMA, potentially leading to discoveries of newly formed planets within the GW Orionis system. In turn, theories about such formation mechanisms could uncover an as-yet unknown population of exoplanets in binary and tertiary systems.
The research is described in Science.


physicsworld--2020-09-21--COVID Research and Resources Group brings physicists together - Physics World

Physics has an important role to play in tackling the COVID-19 pandemic .
Many physicists are already contributing to COVID-related research , in areas including computational modelling , medical imaging and development of protective and therapeutic equipment .
Many such physicists are working in isolation , however , and only interacting on a local level .
The newly formed COVID Research and Resources Group ( CRRG ) aims to bring these physicists and related researchers together , allowing them to benefit from a more coordinated approach .
Leading the initiative is Robert Jeraj , professor of medical physics at the @ @ @ @ @ @ @ World how the CRRG originated : “ The American Physical Society [ APS ] has a Topical Group on Medical Physics , GMED , and we had a discussion about how we can help to bring together physicists that are interested in COVID-related research , those already doing research and those who want to contribute and share resources .
Partnering with many other APS units , this turned into the COVID Research and Resources Group.
” The CRRG aspires to be a global initiative , connecting physicists , engineers , and other medical @ @ @ @ @ @ @ worldwide .
To achieve this , it created an online community on the APS Engage platform where members can share ideas and conduct discussions .
Jeraj notes that this group , which now has 100 members , is not limited to physicists or APS members but is open to anyone to join .
Established back in the summer , the first job for the CRRG organizing committee was to understand the needs of the community and set up resources and initiatives to meet these needs .
The first idea to emerge from their @ @ @ @ @ @ @ webinars , which will launch later this week , on 23 September .
The webinars are aimed at a broad audience , from college students upwards , and will be presented by experts , at a level that ’ s understandable to non-experts .
The first speaker will be epidemiologist Marc Lipsitch , director of the Center for Communicable Disease Dynamics at Harvard University .
Lipsitch will describe key features of the epidemiology of the COVID-19 pandemic , focusing on the complexity of the data-generating mechanisms .
“ For the first talk , @ @ @ @ @ @ @ the stage , to present the problem in a form that physicists can respond to , ” explains Jeraj .
“ We ’ ve seen a lot of physicists wanting to help , but either not having access to the data or not understanding the challenges of the publicly available dataset .
Marc Lipsitch has had a career in modelling data , he understands the heterogeneity of data , the difficulties of obtaining data and the impact of data imperfections on the model outcome .
He can explain the current challenges ; physics @ @ @ @ @ @ @ APS COVID webinars will continue on a fortnightly basis , with the next three speakers already lined up ( see box below ) .
Members are encouraged to use the CRRG community website to suggest questions ahead of time and then discuss the webinar coverage afterwards .
In addition , some of the presenters will also create webinars aimed at high-school students and provide resources for physics teachers .
The CRRG also plans to conduct a survey to determine future topics and gather suggestions for additional speakers .
Another project involves a “ @ @ @ @ @ @ @ to highlight high-impact papers .
In partnership with Johns Hopkins University , the CRRG aims to create a library of the most important research .
“ COVID-19 research is an area where I think medical physics needs to be heavily engaged , ” says Jeraj .
“ I feel responsibility to dedicate my time to this.
” Marc Lipsitch , professor of epidemiology and director of the Center for Communicable Disease Dynamics at Harvard University .
23 September , 12.00 ET What we know and don ’ t know about SARS-CoV-2 : physics @ @ @ @ @ @ @ the Program for Mathematical Genomics and director of the Center for Topology of Cancer Evolution and Heterogeneity at Columbia University .
7 October , 12.00 ET What we know and don ’ t know about the role of droplets and aerosol transmission of SARS-CoV-2 Adriaan Bax , section chief of the Biophysical NMR Spectroscopy Section at the National Institutes of Health .
21 October , 12.00 ET Benjamin Greenbaum , associate attending in the Computational Oncology Service at Memorial Sloan Kettering Cancer Center .
4 November , 12.00 ET Details of forthcoming webinars @ @ @ @ @ @ @ Webinar Series web page , which also provides instructions for joining the CRRG community on the APS Engage platform .

The newly formed CRRG will bring together physicists, engineers, and other medical and biological experts to collaborate on COVID-19 research. (Courtesy: iStock/RomoloTavani)
Physics has an important role to play in tackling the COVID-19 pandemic. Many physicists are already contributing to COVID-related research, in areas including computational modelling, medical imaging and development of protective and therapeutic equipment. Many such physicists are working in isolation, however, and only interacting on a local level. The newly formed COVID Research and Resources Group (CRRG) aims to bring these physicists and related researchers together, allowing them to benefit from a more coordinated approach.
Robert Jeraj.
Leading the initiative is Robert Jeraj, professor of medical physics at the University of Wisconsin–Madison. He tells Physics World how the CRRG originated: “The American Physical Society [APS] has a Topical Group on Medical Physics, GMED, and we had a discussion about how we can help to bring together physicists that are interested in COVID-related research, those already doing research and those who want to contribute and share resources. Partnering with many other APS units, this turned into the COVID Research and Resources Group.”
The CRRG aspires to be a global initiative, connecting physicists, engineers, and other medical and biological experts from groups and societies worldwide. To achieve this, it created an online community on the APS Engage platform where members can share ideas and conduct discussions. Jeraj notes that this group, which now has 100 members, is not limited to physicists or APS members but is open to anyone to join.
Established back in the summer, the first job for the CRRG organizing committee was to understand the needs of the community and set up resources and initiatives to meet these needs. The first idea to emerge from their brainstorming was a series of APS COVID webinars, which will launch later this week, on 23 September.
The webinars are aimed at a broad audience, from college students upwards, and will be presented by experts, at a level that’s understandable to non-experts. The first speaker will be epidemiologist Marc Lipsitch, director of the Center for Communicable Disease Dynamics at Harvard University. Lipsitch will describe key features of the epidemiology of the COVID-19 pandemic, focusing on the complexity of the data-generating mechanisms.
“For the first talk, we wanted to have somebody to set the stage, to present the problem in a form that physicists can respond to,” explains Jeraj. “We’ve seen a lot of physicists wanting to help, but either not having access to the data or not understanding the challenges of the publicly available dataset. Marc Lipsitch has had a career in modelling data, he understands the heterogeneity of data, the difficulties of obtaining data and the impact of data imperfections on the model outcome. He can explain the current challenges; physics can then bring the solutions.”
The APS COVID webinars will continue on a fortnightly basis, with the next three speakers already lined up (see box below). Members are encouraged to use the CRRG community website to suggest questions ahead of time and then discuss the webinar coverage afterwards. In addition, some of the presenters will also create webinars aimed at high-school students and provide resources for physics teachers. The CRRG also plans to conduct a survey to determine future topics and gather suggestions for additional speakers.
Another project involves a “post-review” of recently published COVID-19 literature to highlight high-impact papers. In partnership with Johns Hopkins University, the CRRG aims to create a library of the most important research.
“COVID-19 research is an area where I think medical physics needs to be heavily engaged,” says Jeraj. “I feel responsibility to dedicate my time to this.”
The APS COVID webinars Epidemiology of COVID-19: Implications for control Marc Lipsitch, professor of epidemiology and director of the Center for Communicable Disease Dynamics at Harvard University. 23 September, 12.00 ET What we know and don’t know about SARS-CoV-2: physics of viruses Raul Rabadan, director of the Program for Mathematical Genomics and director of the Center for Topology of Cancer Evolution and Heterogeneity at Columbia University. 7 October, 12.00 ET What we know and don’t know about the role of droplets and aerosol transmission of SARS-CoV-2 Adriaan Bax, section chief of the Biophysical NMR Spectroscopy Section at the National Institutes of Health. 21 October, 12.00 ET Immune interactions and SARS-CoV-2 evolution Benjamin Greenbaum, associate attending in the Computational Oncology Service at Memorial Sloan Kettering Cancer Center. 4 November, 12.00 ET Details of forthcoming webinars can be found on the APS COVID Webinar Series web page, which also provides instructions for joining the CRRG community on the APS Engage platform.


physicsworld--2020-09-21--Thermal diodes bridge the gap - Physics World

Electronic devices are hard to keep cool .
Mechanical fans suck up energy .
Heat sinks add unwanted bulk and mass .
And thermal diodes – devices that allow heat to flow more easily in one direction than the other – are fragile , inefficient and require gravity to operate .
Now , however , a new type of thermal diode looks set to overcome some of these drawbacks , with developers at Virginia Tech in the US suggesting that a future commercialized version could help manage heat in computer chips and aircraft components .
The directional thermal effect was @ @ @ @ @ @ @ physicist Chauncey Starr of the Rensselaer Polytechnic Institute in New York developed a thermal diode based on a copper-cuprous oxide interface .
The new device , dubbed a “ bridging-droplet ” diode , consists of two opposing copper plates separated by an insulating micron-thick gasket .
The surface of the first plate has a wick-like structure consisting of micropillars that hold and conduct water .
The second plate , meanwhile , is coated with a water-repelling layer .
In the diode ’ s forward operation mode , water on the wicking plate absorbs @ @ @ @ @ @ @ steam .
The steam propagates across the narrow gap between the plate and condenses into dew-like droplets on the hydrophobic plate .
When the droplets grow large enough to bridge the gap , they get sucked back into the wick structure , starting the process anew .
During the device ’ s reverse mode of operation , the situation is different .
In this case , the heat source is now on the hydrophobic plate , but no steam can be produced because the water remains in the wicking structure on the other @ @ @ @ @ @ @ explains team leader Jonathan Boreyko , is what allows the device to conduct heat unidirectionally .
The new device can also be used upright , sideways or even upside-down and would thus work just as well in space .
The researchers measured the ratio of heat transferred from the wick side to the hydrophobic side – a quantity known as “ diodicity ” – to be as high as 85 .
While assymmetric heat pipes offer an even larger diodicity of around 100 , their 1D heat transfer is ineffective for large 3D @ @ @ @ @ @ @ array of directional heat pipes into a wall panel solves this problem , but this is both complex and decreases the effective diodicity by more than a factor of 10 , he explains .
Boreyko notes that the water-repellent coating he and his colleagues used to create their test device ( a mixture of 1-hexadecanethiol in ethanol ) is not suitable for practical applications .
However , he says this coating could be replaced with more durable alternatives such as graphene or grafted polymers .
This gives the Virginia Tech device a potential @ @ @ @ @ @ @ as a “ jumping-droplet ” thermal diode , which requires a fragile superhydrophobic nanostructure to operate .
Members of the team , who report their work in Advanced Functional Materials , have filed a provisional patent for their diode and are now looking to collaborate with industry partners to continue the research .
One of the items on their to-do list is to boost the diodicity of their device to 100 .
This could be achieved , for example , by decreasing the height of the micropillars so that smaller droplets could bridge @ @ @ @ @ @ @ plates .
The researchers would also like to test more durable hydrophobic coatings .

Lab member Mojtaba Edalatpour shows the thermal diode developed by Boreyko's team. Credit: Virginia Tech
Electronic devices are hard to keep cool. Mechanical fans suck up energy. Heat sinks add unwanted bulk and mass. And thermal diodes – devices that allow heat to flow more easily in one direction than the other – are fragile, inefficient and require gravity to operate. Now, however, a new type of thermal diode looks set to overcome some of these drawbacks, with developers at Virginia Tech in the US suggesting that a future commercialized version could help manage heat in computer chips and aircraft components.
The directional thermal effect was first observed in the 1930s, when physicist Chauncey Starr of the Rensselaer Polytechnic Institute in New York developed a thermal diode based on a copper-cuprous oxide interface. The new device, dubbed a “bridging-droplet” diode, consists of two opposing copper plates separated by an insulating micron-thick gasket.
The surface of the first plate has a wick-like structure consisting of micropillars that hold and conduct water. The second plate, meanwhile, is coated with a water-repelling layer. In the diode’s forward operation mode, water on the wicking plate absorbs heat from its surroundings and evaporates into steam. The steam propagates across the narrow gap between the plate and condenses into dew-like droplets on the hydrophobic plate. When the droplets grow large enough to bridge the gap, they get sucked back into the wick structure, starting the process anew.
A “diodicity” as high as 85
During the device’s reverse mode of operation, the situation is different. In this case, the heat source is now on the hydrophobic plate, but no steam can be produced because the water remains in the wicking structure on the other plate. This transfer of water, explains team leader Jonathan Boreyko, is what allows the device to conduct heat unidirectionally. The new device can also be used upright, sideways or even upside-down and would thus work just as well in space.
The researchers measured the ratio of heat transferred from the wick side to the hydrophobic side – a quantity known as “diodicity” – to be as high as 85. While assymmetric heat pipes offer an even larger diodicity of around 100, their 1D heat transfer is ineffective for large 3D systems, Boreyko says. Placing an array of directional heat pipes into a wall panel solves this problem, but this is both complex and decreases the effective diodicity by more than a factor of 10, he explains.
Boreyko notes that the water-repellent coating he and his colleagues used to create their test device (a mixture of 1-hexadecanethiol in ethanol) is not suitable for practical applications. However, he says this coating could be replaced with more durable alternatives such as graphene or grafted polymers. This gives the Virginia Tech device a potential advantage over a conceptually similar device known as a “jumping-droplet” thermal diode, which requires a fragile superhydrophobic nanostructure to operate.
Members of the team, who report their work in Advanced Functional Materials, have filed a provisional patent for their diode and are now looking to collaborate with industry partners to continue the research. One of the items on their to-do list is to boost the diodicity of their device to 100. This could be achieved, for example, by decreasing the height of the micropillars so that smaller droplets could bridge the insulating gap between the two copper plates. The researchers would also like to test more durable hydrophobic coatings.