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Multidisciplinary collaboration: the engine-room of opportunity

Like many postgraduate physicists, Hannah Hare was confronted with the classic stick-or-twist dilemma upon completion of her PhD studies at the University of Oxford, UK. Stick would have meant following the traditional academic path – most likely building on and developing her graduate research on the use of noninvasive functional MRI techniques to enhance diagnosis and treatment of stroke patients. She decided to twist, as it turns out, and headed in an altogether different direction after securing a role as a scientific consultant at TTP, an independent technology company where a multidisciplinary staff of 230+ scientists and engineers delivers breakthrough product innovations for clients across a range of industries – from telecoms and computing to healthcare and advanced manufacturing.

What attracted Hare to TTP is a working model that starts and ends with multidisciplinary collaboration. “I really got the sense that I’d continue to learn and do all sorts of new science here,” she explains. “After completing my PhD, I knew I didn’t want to end up as a hyper-specialist within a large R&D organization, making incremental improvements in a narrow field of research.”

Since making the transition to industry in 2015, Hare has grasped the opportunity to broaden her experience at the interface between science, engineering and business. Working as part of TTP’s Sensors and Devices group, she focuses largely on new biosensing technologies for healthcare applications – for example, blood glucose sensors, blood pressure monitors and neurostimulation devices. “The common thread here is you’re working on product innovations that are close to market,” Hare adds, “so TTP is a great place for someone who wants to stay in an R&D environment but also have an impact on the real world – whether that’s for our clients, their customers or patients [in the case of the biosensing programme].”

Focusing on impact

Operationally, TTP is structured around custom R&D projects for a diverse client base, ranging from technology start-ups to established blue-chip organizations. While customer-facing activity predominates, there are also many internal R&D projects under way at any one time, some of which will yield spin-out technologies and new commercial opportunities – for example, TTP’s LEX thermal control technology for DNA amplification in point-of-care diagnostics.

Hannah Hare: “Physicists do a lot of work designing and running experiments at TTP. The task is to figure out what is it we know, what is it we don’t know, and how can we discover the things we need to know that we don’t know yet.” (Courtesy: TTP)

Given that backdrop, every day is different for TTP consultants, whether they’re working in the lab – performing experiments or running computer simulations to elucidate the underlying physics of a customer problem – or out in the field pitching the business to prospective clients. “As a new consultant,” notes Hare, “you’re part of the conversation with the client very early on.”

It’s a steep learning curve. As well as getting to grips with a broad spectrum of new science, there’s the effective communication of that science – with the emphasis on interpretation, analysis and recommendation over granular technical information. Is there a market for this technology? Can this new product deliver the desired price:performance at scale? What other technology options can achieve the desired outcomes?

“These are the sorts of questions that TTP consultants seek to answer,” says Hare. “It’s a big culture change for sure: the shift from writing academic papers – essentially for other experts in your field – to concise business reports and presentations that address the commercial questions and concerns our clients really care about.”

Translational science

That commercial mindset also frames and informs the multidisciplinary conversations that happen day in, day out at TTP. (In normal times, all of the firm’s consultants are co-located at TTP headquarters near Cambridge, UK, though most staff are currently working from home as a result of the Coronavirus restrictions.) “It’s a two-way street – you learn from your colleagues and they learn from you,” Hare says of the firm’s collaborative culture, while at the same time acknowledging that not all scientists and engineers speak the “same language”.

“I have found that biologists and engineers, for example, sometimes struggle to understand one another during the early phases of a project,” Hare explains. “They use different words for similar things, but more crucially their focus is very different.” Biologists need to keep “pesky little cells alive at all costs”, she notes, and the way that different molecules and cells interact with each other is often unpredictable, making the development of new diagnostics challenging and unpredictable. Engineers, by contrast, tend to lay out detailed plans and follow them linearly, as their work is more predictable and often highly regulated.

Physicists fall perfectly between these two extremes, making them ideally placed for “translation” between fundamental scientific research – whether internal to TTP or carried out by its clients – and the needs of high-volume, robust and reliable engineering. “This interface is where the biggest opportunities lie, bringing together different disciplines to create truly ground-breaking new products,” Hare adds. “It means we as physicists are able to learn from both ends of the spectrum, explain the needs of one discipline to another, and help make crucial decisions to balance conflicting requirements such as accuracy, cost, reliability, lifetime, development time and commercial risk.”

That upside extends to the many clients who approach TTP having already demonstrated a new lab technique but needing to scale up to a commercially viable product. “In these cases,” says Hare, “physicists are usually first on the scene, understanding from our clients how their technology works and where its limits lie, so that we can develop a set of requirements to pass on to the engineers.”

Personal growth = commercial growth

From an employee perspective, a unique and attractive aspect of TTP is its flat management structure, with most consultants having a direct stake in the business (the firm is privately owned by current and former employees). As such, the company prioritizes autonomy and self-directed personal development and career progression.

Consultants, for example, will often lead on one project while providing lab-based support on several others. Hare is a case in point. After just six months in post, she led a project to design a new blood-pressure monitor and has since progressed to more complex briefs with bigger teams and bigger budgets. Right now, she heads a project to develop a low-cost disposable device for peripheral nerve stimulation – a collaboration with Neurent Medical, a start-up based in Galway, Ireland. The aim is to come up with a clinically approved treatment for rhinitis (an allergic inflammation of the inside of the nose) by stimulating nasal nerves with a small amount of electricity.

You’re not micromanaged here. There’s a lot of freedom to pursue the career track that best fits your skill-set.
Hannah Hare, TTP

“You’re not micromanaged here,” says Hare. “There’s a lot of freedom to pursue the career track that best fits your skill-set. Day-to-day there’s also a lot of variety – a morning of lab work might be followed by a few hours drafting a client pitch or a brainstorming session with colleagues on a new project.”

Hare, for her part, has gravitated towards business development activities, on which she currently spends most of her time. She’s currently applying her background in neuroscience and medical imaging, alongside TTP’s engineering know-how, to develop commercial opportunities in neural interfaces – whether that’s smart brain implants to reduce the life-limiting symptoms of Parkinson’s disease or novel noninvasive techniques to help patients with neurological conditions such as Alzheimer’s, severe depression or epilepsy.

While the commercial objectives are clear, this is slow-build, client-facing work that requires direct engagement with established manufacturers and start-ups in the medical device sector – though it’s often the latter pushing truly game-changing innovations. “Putting together a full team for hardware development is a massive undertaking for any start-up,” says Hare, adding that this is where TTP comes into its own by providing a tailored science and engineering team to match their ambitions.

“Ultimately,” she concludes, “it’s the combination of skill sets – from fundamental science to large-scale engineering – that sets us apart, that allows us to create ground-breaking new technologies, and that makes TTP such an exciting place to work.”

• Find out more about TTP careers and current vacancies at Why TTP

Graphene quantum dots could treat autoimmune disorders

Quantum dots made from graphene could be used to treat the inflammatory bowel disease ulcerative colitis, a study in a mouse model has found. Graphene quantum dots (GQDs) effectively regulated the excessive immune response that is characteristic of ulcerative colitis, reducing intestinal inflammation and preventing tissue damage. This finding indicates that GQDs are promising therapeutic agents for the treatment of autoimmune disorders, the researchers say.

At least 300,000 people in the UK have ulcerative colitis or Crohn’s disease – the two main forms of inflammatory bowel disease. These autoimmune diseases can cause inflammation, swelling and ulceration of the digestive system. Ulcerative colitis affects the rectum and colon, while Crohn’s disease can affect any part of the digestive system.

There is no known cure for these life-long conditions. Patients can experience a range in severity of symptoms, with treatments including surgery and medication, such as immunosuppressants and biological therapies that target the immune system. But there are risks in taking these powerful drugs, particularly of catching serious and opportunistic infections, and developing cancers. Alternative therapeutics with less side effects are urgently needed.

Kyung-Sun Kang, director of the Adult Stem Cell Research Center at Seoul National University in South Korea, explains that inflammatory bowel diseases are characterized by a “hyperimmune state”, with over-active macrophages and T cells. “T helper cells produce inflammatory cytokines in ulcerative colitis and you then have inflammation in the intestine,” he explains.

There is previous evidence to suggest that GQDs have an impact on the immune system and now Kang and Byung Hee Hong, head of the Graphene Research Laboratory at Seoul National University, have found that they reduce intestinal inflammation in mice models of ulcerative colitis by suppressing excessive T cell activity. They also found that the GQDs switch the macrophages involved in the inflammatory response to a different type of macrophage that regulates the immune system. GQDs appear to “help maintain a homeostatic balance in the immune system”, Kang says.

For their study, described in Science Advances, Kang, Hong and colleagues injected GQDs with an average size of 29 nm into the abdominal cavity of colitis model mice. GQD-treated mice had increased survival rates and reduced weight loss compared with untreated mice, and scored lower on a disease activity index based around weight loss, activity, stool consistency, bleeding and hair condition. They also had lower levels of a biomarker of ulcerative colitis and reduced shortening of the colon – a characteristic feature of the disease.

When the team looked at levels of cytokines in the mice, they found marked reductions in interferon-γ, the major cytokine involved in inflammatory bowel disease, in mice treated with GQDs. These animals also had lower levels of other pro-inflammatory cytokines. The researchers conclude that the GQDs had preventive and therapeutic effects, and reduced disease severity.

The exact mechanism behind the immune regulation is still unclear, but Hong tells Physics World that GQDs have very interesting properties that probably enable it to stabilize the immune system. This is likely to be due to their known powerful antioxidant effect and ability to scavenge reactive oxygen species, which helps reduce inflammation, and their random, non-universal structure that seems to stop them provoking an immune response.

The GQDs showed negligible toxicity and were naturally cleared from the mice. “We increased the concentration up to 100 times more than the therapeutic condition, and all the mice survived,” Hong says. “In addition, we confirmed that GQDs are excreted through urine in a few weeks without accumulation in any organs.”

The team is now looking to develop an oral version of the therapy and moving towards clinical trials. “After studying the pre-clinical research this year, we are targeting stage 1 clinical trials in 2022,” Hong tells Physics World.

Ministry of Recovery and Discovery

Am I the only one who thinks that perhaps some of our technology has come too far, too fast? And are we really better off as a result of this? Whenever I bring up the subject among friends and colleagues it invariably results in my being told to “get back to the dark ages” (which I’m old enough to remember). If I have interpreted the current general opinion correctly, it’s that all progressive technology is good, and that rather than eventually making us redundant and supine, the world without it would be a very dark place indeed.

So, when I become World Leader, my first task will be to establish a Ministry of Recovery and Discovery (MoRD). This novel ministry will continue to produce inventions of benefit to mankind, but with the restriction that they do no harm to the planet – for example, by leaving a trail of pollution. Simultaneously, it will tackle the removal of those insidious evolutions that threaten our well-being and that of our planet.

One of the first challenges for the MoRD will be to remove all traces of the internal combustion engine. As a major source of pollution worldwide, its demise would greatly help the environment and would herald a new era of opportunity and challenge. Companies manufacturing things such as bicycles and horseshoes would receive a boost, and what a joy it would be to hear the soothing clatter of hooves making their way along the smooth motorway surfaces, mingled with the soft purr of the electric vehicles developed to fill the needs of emergency services and public service providers. Of course, a new breed of highly efficient, high-capacity batteries would be developed to replace the lithium cell, and the positively archaic lead-acid museum piece.

An important follow-up task for the MoRD would be the removal of any residual legacy left by petrol and diesel cars – perhaps by removing carbon dioxide from the atmosphere using the relatively cheap and efficient direct air capture method, which is currently being pioneered at a few locations, including Cambridge in the UK. At the same time, the ministry’s botany team would be striving to perfect a new breed of trees and plants with enhanced powers of photosynthesis, giving at least twice the capacity for oxygen production.

Further strong candidates for removal include plastics, mobile telephones and nuclear power. Both nuclear power and plastics share the same virtually insoluble problem of waste disposal. The indestructible nature and consequent build-up of long-half-life nuclear waste, the potential for accidental radiation hazard and the proliferation of nuclear weaponry no longer makes nuclear power an attractive option. The current estimate of high-level waste held worldwide is in excess of a quarter of a million tonnes and rising, which is a lot of dangerous material to have around, whether deeply buried, launched into space, submerged beneath the oceans, or elsewhere.

Plastic, with its indestructible nature and ability to insinuate itself into the very fabric of our planet at an alarming rate, has more than outlived its initial usefulness. The diverse scale of its use – from the majority of packaging, to low-friction bearings, to polypropylene used to ensure the physical integrity of the humble tea bag even – leaves a formidable plastics legacy of pollution and destruction. Research at the MoRD to earnestly develop a truly recyclable, biodegradable replacement will be a priority. In the interim period, tea drinkers will need to resort to the faithful tea pot – and with growing sales the emergence of a new, attractive, heat-retaining, truly non-drip tea pot would be welcomed by tea drinkers everywhere.

Of the various clean forms of energy, wind, solar and wave seem to have the greatest potential, especially if their efficiency continues to improve. Vertical axis wind turbines (VAWTs) are particularly versatile, without the need to “track the wind” by yawing the rotor or pitching the blades. Easier maintenance than the horizontal equivalent is assured as generator and gearbox can be positioned at ground level. This also makes them an attractive proposition for the domestic situation, inviting initiatives such as collaboration with rotary clothesline manufacturers. VAWTs are generally longer-lasting, cheaper, can be situated closer together and have higher power outputs than horizontal-axis versions.

Research into the biological effects, if any, of microwave radiation associated with mobile telephones has continued to be minimal and inconclusive since the 2000 Stewart report by the Independent Expert Group on Mobile Phones (IEGMP). Biologist William Stewart concluded, quite correctly, that there was no evidence that such microwave radiation had any harmful effect on humans – much to the relief of mobile phone manufacturers – although, interestingly, he advised that the use of mobiles by children should be discouraged. Stewart’s conclusions, of course, offer no guarantee of safety and one recalls how asbestos, X-rays and cigarettes were retrospectively condemned after considerable damage had been done.

With the current world population racing towards eight billion, it is clear where we are heading, and the destination isn’t that attractive. Facing dwindling resources such as air, water, food and space, the MoRD will have to take the initiative to meet this challenging situation if we are to survive, although it will be difficult to come up with a humane and ethical solution.

Droplets created by speech could contribute to COVID-19 spread, new study suggests

Droplet clouds emitted during 1 min of loud speech by an individual infected with the SARS-CoV-2 virus could contain more than 1000 virus particles – according to new calculations done by scientists in the US. This work, alongside observations that these speech-generated droplet clouds persist in a confined space for 8-14 min, supports suspicions that COVID-19 may be transmitted when infected individuals speak.“This direct visualization demonstrates how normal speech generates airborne droplets that can remain suspended for tens of minutes or longer and are eminently capable of transmitting disease in confined spaces,” write the team in a paper in PNAS Brief Report describing the work.

The piggybacking of viral particles (virions) in droplets generated by coughing and sneezing is a recognized route of respiratory virus transmission. However, the role of fluid droplets emitted during speaking is less-well known. Given the current COVID-19 pandemic, this spoken transmission route is attracting considerable attention, particularly in relation to spread from asymptomatic carriers.

Philip Anfinrud and Adriaan Bax’s biochemical physics teams at the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) (part of the National Institutes of Health) in Bethesda, Maryland recently made high resolution visualizations of droplets produced when a person speaks. They described this work in the New England Journal of Medicine.

Visualizing saliva spray

To observe droplets after they are produced by speech, the NIDDK teams used a laser and optics visualization system. The droplets were created by having a person repeat the phrase “stay healthy” several times (with short delays in between) into the “speaker port” of a cardboard box and then capturing the crossing of the droplets through a sheet of intense laser light. The high sensitivity of the system enabled the teams to detect small droplets, 20-100 micron in diameter, and so record a higher volume of droplets than previous studies.

Now the researchers have quantified those experiments to assess the potential for speech droplets to transmit SARS-CoV-2 viral particles in an enclosed environment. In work described in a PNAS Brief Report, Anfinrud and colleagues used an improved experimental setup to derive quantitative estimates for how long the smallest droplets remain airborne and how many there are. where the researchers write.

Careful estimations

The researchers described the droplets using two exponential decay functions, with the top 25% in scattering brightness and the dimmer 75% fraction having exponential decay constants of 8 min and 14 min, respectively.

They used the weighted average decay rate of all droplets to calculate the terminal velocity of the droplets and, given smaller droplets fall at a slower rate (staying airborne for longer), from the velocity they were able to estimate the average fallen droplet size.

The probability a droplet contains a viral particle depends on the initial droplet volume, but evaporation causes a rapid decrease in volume after release from the mouth. The team made shrinkage assumptions based on the relative humidity and temperature of the experimental settings, estimating the initial droplet size to be 12-21 micron in diameter.

The researchers were unavailable for comment, but the NIDDK responded to questions on their behalf. The NIDDK told Physics World that the researchers were “surprised to find the enormous number of particles in the 12-20 micron range [as this was far higher than suggested by previous research] that, after drying out and shrinking to about 4 micron, remain airborne for many minutes”.

Finally, to determine the probability a droplet encapsulates at least one virus, the team estimated the total volume of emitted saliva in their experiments, and combined this with data from recent research that shows saliva from a COVID-19 patient contains on average about seven million virus particles per millilitre.

They found that a second of speaking could be expected to generate 17-90 virion-containing droplets.

Substantial probability of transmission

In their latest paper the authors conclude, “These observations confirm that there is a substantial probability that normal speaking causes airborne virus transmission in confined environments.”

The potential of far-ultraviolet light for the next pandemic

Julian Tang, a virologist at the University of Leicester, UK, who has expertise in respiratory viruses and their transmission, comments that this work is a “nice visualization method”. But points out that it would be “even more powerful” if the researchers combined their expertise with other disciplines to quantify live virus transported by speech droplets from COVID-19 infected volunteers.

The NIDDK says that Anfinrud and Bax’s team are building a third-generation laser-scattering apparatus to further address questions regarding speech droplet transmission.

The mystery of missing marine plastic

In the May 2020 issue of Physics World, science journalist Marric Stevens wrote about the problem of the missing plastic in the world’s oceans. Although we are starting to see large amounts of plastic in the oceans, the quantity is far smaller than we expect to see – based on the quantities of plastic being released into the oceans every year. In the latest episode of the Physics World Stories podcast, Andrew Glester digs deeper into the mystery to find out where the plastic might be ending up.

To learn about the threat of plastic to marine wildlife, Glester meets Lucy Quinn, a seabird ecologist with the British Antarctic Survey. Quinn was the researcher who captured public awareness of the plastics issue when she appeared in the BBC’s Blue Planet 2 showing the horrific impacts of ingested plastic on an Albatross colony in Bird Island, South Georgia.

Also in the podcast, physical oceanographer Erik van Sebille outlines the extent of the missing plastics issue. He explains how his research on ocean flow at Utrecht University in the Netherlands can help to better understand where the plastics are ending up. While Alethea Mountford from Newcastle University, UK, describes how oceanographers combine physical measurements with modelling to get a handle on the issue.

To find out more, read ‘The search for the missing plastic‘, a feature originally published in the May 2020 issue of Physics World – a special edition on plastic waste.

This podcast is sponsored by Teledyne Hastings Instruments.

The Cassini spacecraft mission at Saturn

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In September 2017, the NASA/ESA Cassini-Huygens spacecraft mission ended its 20 years in space by burning up in Saturn’s atmosphere. The end-of-mission orbits was designed to better understand the interior of Saturn and its magnetic field.

ICL webinar — (Courtesy: NASA/JPL-Caltech)

This webinar will describe these end-of-mission results as well as some of the other surprising discoveries made during the orbital tour at Saturn, including water-vapour plumes at the small moon Enceladus and implications that this has for potential habitability.

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Michele Dougherty is professor of space physics at Imperial College London. She is leading unmanned exploratory missions to Saturn and Jupiter, and was the principal investigator for the magnetometer instrument onboard the Cassini mission to Saturn as well as being the principal investigator of the magnetometer for the JUpiter ICy moons Explorer (JUICE) of the European Space Agency due for launch in June 2022. She is head of the physics department, is a fellow of The Royal Society, was awarded the Royal Astronomical Society Geophysics Gold Medal in 2017, was awarded a CBE in the 2018 New Year Honours list, and was awarded the Institute of Physics Richard Glazebrook Gold Medal and Prize.

Tipsy sludge worms simulate active polymers

Clumps of wriggling – and sometimes drunken – sludge worms have been used by physicists in the Netherlands to simulate the behaviour of self-moving polymers. Antoine Deblais and colleagues at the University of Amsterdam used the creatures to gain new insights into the properties of poorly understood “active polymer” materials by measuring the viscosity of worm clusters as they were subjected to shear forces.

Polymers such as silk and polyester are some of the most familiar and most studied materials. However, scientists know much less about active polymers, which use stored energy or energy in the surrounding environment to move and change shape. When active polymers interact with each other and the fluid surrounding them, new structures and dynamics can emerge – something that could be useful for developing new technologies. However, studying this in the lab or using computer simulations is extremely challenging.

Now, Deblais’ team has used tangled clusters of living sludge worms as an analogue system for studying active polymers. These long, slender animals closely mimic the behaviours of active polymer molecules, and are also widely available in many pet shops, making them ideal for simple, inexpensive experiments. Furthermore, their activity can be varied by placing them in water at different temperatures, and they can even be temporarily incapacitated when exposed to alcohol – allowing them to resemble inactive polymers more closely.

Disentangling freely

In their experiment, Deblais and colleagues studied the physical properties of the worms by putting them in a shallow cylindrical container of water. They then pressed a rotating plate onto the surface of the mixture, subjecting it to a shear force. In a typical polymer, tangling between molecules would resist these forces, increasing the viscosity of the mixture. In contrast, the movements of the worms caused any coils to disentangle more freely. This meant the warmer mixtures, which contained the most active worms, were up to 100 times less viscous than those containing inactive, alcohol-infused specimens.

The team also looked at an effect called“shear thinning”, which occurs when higher shear forces force the polymer strands to align themselves, thereby lowering the viscosity. In contrast, Deblais’ team found that mixtures containing more active worms displayed less shear thinning than their inactive counterparts when the plate was spun at several rotations per second. They believe that this occurs as the bending, stretching, and contracting motions of the wriggling worms works against the alignment process.

Deblais and colleagues now hope that their research will pave the way for a new experimental research field they call “polymer-like worms”, which could lead to much better models of similar systems on microscopic scales. Their research could also lead to sophisticated new techniques for modelling a variety of microscopic biological systems.

The research is described in Physical Review Letters.

Nano-optomechanical resonator detects low-frequency bacteria vibrations

Researchers in Spain and France have measured the vibrations of individual bacteria by coupling them to a nanomechanical device with a similar resonance frequency. This new optomechanical spectrometry technique could offer an alternative to current methods of detecting and classifying bacteria and other biological particles.

Proteins, viruses and bacteria all vibrate at frequencies in the terahertz and gigahertz range. Their vibrations carry valuable information about their structure and mechanical properties, but efforts to study these using optical inelastic scattering techniques are extremely challenging because the bioparticles change shape and deform as they vibrate.

The new method, developed by a team led by Javier Tamayo and Eduardo Gil-Santos from the Instituto de Micro y Nanotecnología (IMN-CSIC) in Madrid, involves coupling the mechanical vibrations of bacteria to an ultrahigh frequency (UHF) nano-optomechanical resonator made from a GaAs microdisk. Such coupling is only possible when the resonance frequencies of the disk and the bacteria are similar, Tamayo explains. In contrast, previous experiments relied on the biological particles vibrating much faster than the micro- and nanomechanical resonators or microcantilevers used to measure the particles’ mass and stiffness.

Going beyond mass and stiffness measurements

The Madrid team’s disks support two different types of vibration: radial breathing modes (RBMs), which correspond to a radial expansion and contraction of the disk (and therefore depend on its diameter), and so-called optical whispering gallery modes, which correspond to resonances within the disk’s structure. In both cases, the disk vibrates at frequencies in the GHz range, which can actually surpass the low-frequency vibration modes of bioparticles.

In their experiments, Tamayo and colleagues deposited a single S. epidermis bacterium onto their optomechanical microdisks using an electrospray ionization technique. The bacteria are round in shape and have a radius of roughly 400 nm. The researchers measured the fundamental RBM frequencies of the disks before and after depositing the bacteria, then used a general theoretical framework to describe the coupling between the bacteria and the disks. This framework allowed them to calculate the resonant frequencies of a bacterium’s low-frequency vibration modes based on their “before and after” measurements of the disks’ RBM frequencies.

To determine the mechanical coupling between a bacterium and their nanomechanical resonator, the researchers had to measure very tiny fluctuations – a few picometres (10^-12 m) – at ultrahigh frequencies. Such measurements were only possible thanks to the strong optomechanical coupling of the disks to the bacterium. Indeed, the coupling is so strong that these devices can measure displacements of just attometres (10^-18 m) – a value similar to the precision of the kilometre-sized interferometers used to measure gravitational waves, Tamayo says.

The work was done within the framework of the EU FE VIRUSCAN project, which aims to use optomechanical resonators to detect viral particles based on their physical parameters. The idea is to build up a “library” of the mechanical and vibrational properties of different viruses and bacteria.

Members of the Madrid team, who report their work in Nature Nanotechnology, are now planning to use their technique to measure the vibration modes of viruses, which are much smaller than bacteria. “This future work will be more challenging,” Tamayo tells Physics World.

Dual-layer spectral CT proves feasible for routine practice

© AuntMinnieEurope.com — © *AuntMinnieEurope.com*

Reduced-dose dual-layer spectral CT (DLCT) is feasible in routine practice, despite the required higher tube potential, researchers from Heidelberg University Hospital, Germany, reported in a study published in European Radiology.

DLCT can deliver comparable objective and subjective image quality to that of reduced-dose single-layer CT (SLCT), reported Thuy Duong Do, senior physician at the Clinic for Diagnostic and Interventional Radiology, and colleagues. Also, further dose reduction in the thorax might be possible by adjusting mAs thresholds.

Conventional CT acquires images in a single broad energy band, but spectral CT separates energy into two or more narrow energy bands. Because different types of energies are absorbed differently by tissues, they can provide insights into the different chemical compositions of tissues.

“DLCT acquisitions allow material decomposition (virtual non-contrast, iodine-only imaging and effective atomic numbers) as well as the calculation of virtual monoenergetic images,” noted the authors, adding that several clinical studies have shown the benefits of DLCT for head CT to image intracerebral lesions and haemorrhage, for thoracic CT, for vertebral CT to differentiate bone lesions, and for abdominal CT angiographies to improve delineation of visceral arteries.

“For the image acquisition of such data, a tube potential of either 140 kVp or 120 kVp is necessary to allow for spectral decomposition under the exploitation of the energy-specific X-ray absorption of different materials,” they explained. “In contrast to changes in tube current, changes in tube potential have a nonlinear effect on radiation dose.”

Study details

The Heidelberg group’s overall aim was to quantitatively and qualitatively evaluate image quality in DLCT compared with SLCT in the thorax, abdomen and pelvis in a reduced-dose setting.

Example images — Examples of regions-of-interest used for the quantitative evaluation in the thorax at the height of the tracheal bifurcation (left), the upper abdomen at the height of the portal vein (centre), and the lower abdomen at the level of the lumbar spine L4 (right). (Courtesy: *European Radiology*)

The researchers performed intra-individual, retrospective comparisons in 25 patients who received at least one acquisition of all three acquisition protocols – SLCT_low (100 kVp, iCT, Philips Healthcare), DLCT_low (120 kVp) and DLCT_high (120 kVp, IQon Spectral CT, Philips Healthcare) – covering the venous-phase thorax, abdomen and pelvis with matched volumetric CT dose index between SLCT_low and DLCT_low.

All examinations were conducted in the craniocaudal direction and supine position, with automatic exposure control, using an iohexol contrast agent (Accupaque 350, GE Healthcare). Contrast agent application was performed using a power injector with an injection rate of 3 ml/s.

Reconstruction parameters were identical for every scan. Image quality was assessed quantitatively at 10 measurement locations in the thorax, abdomen and pelvis by two independent observers, and subjectively with an intraindividual forced-choice test between the three acquisitions. The authors extracted dose–length product (DLP) and volumetric CT dose index (CTDI_vol) for dose comparison.

The main findings were as follows:

Despite matched CTDI_vol in acquisition protocols, CTDI_vol and DLP were lower for SLCT_low compared with DLCT_low and DLCT_high (DLP of 408.58, 444.68, 647.08 mGy·cm, respectively; p < 0.0004), as automated tube current modulation for DLCT_low reached the lower limit in the thorax (mean 66.1 mAs vs limit 65 mAs).
Noise and contrast-to-noise ratio (CNR) were comparable between SLCT_low and DLCT_low (p values, 0.29–0.51 and 0.05–0.20), but CT numbers were significantly higher for organs and vessels in the upper abdomen for SLCT_low compared with DLCT_low. DLCT_high had significantly better image quality (noise and CNR). Subjective image quality was superior for DLCT_high, but no difference was found between SLCT_low and DLCT_low.
DLCT_low showed comparable image quality to SLCT_low, with the additional possibility of spectral postprocessing. Further dose reduction seems possible by decreasing the lower limit of the tube current for the thorax, the researchers noted.

The team was surprised to see that the transition from 100 kVp to 120 kVp tube potential worked out so well in terms of both image quality and patient radiation exposure, according to corresponding author Stephan Skornitzke, a medical physicist at Heidelberg University Hospital.

“I would have expected that we would lose some contrast with the increase in tube potential, but the contrast-to-noise ratio turned out to be very similar before and after the switch to the new scanner and new protocol,” he told AuntMinnieEurope.com in an email. “Another surprise for me was to see how well the automatic exposure control is able to adjust the tube output to the patient anatomy.”

For the 120 kVp protocols, the exposure control hit the lower threshold for the tube current–time product in the thorax for a number of patients, where it wanted to regulate even lower but could not, he continued.

“This shows us that we can still optimize our acquisition protocols with an attention to detail and reduce patient radiation exposure,” Skornitzke explained. “The automatic exposure control was hitting the lower threshold for the tube current–time product in the thorax for a number of patients. We are in the process of evaluating an adjustment of this lower threshold, which may allow to further reduce patient radiation exposure, especially in smaller patients. However, we will have to carefully consider any potential impact on diagnostic image quality.”

Looking to the future

For follow-up studies based on the spectral imaging capabilities of the CT scanner, the researchers are investigating the potential clinical benefit of the large number of available spectral postprocessing applications. For example, they are evaluating calcium-suppressed imaging, which could allow for more accurate evaluation of bone marrow and fractures.

Also, they are planning to further investigate the connection between automated exposure control, image quality and patient radiation exposure.

“In the context of appropriate imaging, the automated exposure control is a very important tool, as it serves to ensure that the radiation is applied exactly where it is needed,” Skornitzke noted. “Today, with 3D-modulation, online-adaption and specific technologies like ‘Liver Boost’, we have a large number of methods available that help us to guarantee adequate image throughout the scan.”

More research is necessary to evaluate the complex interaction between these technologies, radiation exposure, and image quality, he stated.

The COVID-19 pandemic has provided new challenges for the radiological community regarding the fast and reliable assessment of the associated changes in the lung, and the Heidelberg group is involved in the research of these topics.

“Of course, the pandemic has affected all of our lives. However, as researchers in radiology, we are in a comparatively privileged situation, where our research often involves only a small number of people and a lot of work can be performed digitally, so that our research has so far only been affected minimally,” Skornitzke pointed out.

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New material could be used to make a liquid metal robot

A liquid metal lattice that can be crushed but returns to its original shape on heating has been developed by Pu Zhang and colleagues at Binghamton University in the US. The material is held together by a silicone shell and could find myriad uses including soft robotics, foldable antennas and aerospace engineering. Indeed, the research could even lead to the creation of a liquid metal robot evoking the T-1000 character in the film Terminator 2.

The team created the liquid metal lattice using a special mixture of bismuth, indium and tin known as Field’s alloy. This alloy has the relatively unusual property of melting at just 62 °C, which means it can be liquefied with just hot water. Field’s alloy already has several applications – including as a liquid-metal coolant for advanced nuclear reactors.

Zhang and colleagues combined the alloy with a silicone shell through a complex hybrid manufacturing process that combines 3D printing, vacuum casting and so-called “conformal coating” – a technique normally used to coat circuit boards in a thin polymer layer to protect them against the environment. The silicone shell is what allows the lattice to “remember” a desired shape and restore such when the alloy is melted.

Shell skeleton

“Without the shell, it won’t work, because the liquid metal will flow away,” Zhang said. “The shell skeleton controls the overall shape and integrity, so the liquid metal itself can be confined in the channels.”

To illustrate the potential of the lattice technology, Zhang and colleagues made several demonstration structures – including honeycombs, the letters BUME (for Binghamton University mechanical engineering), a spider web-like mesh and a lattice in the shape of a human hand. When crushed and reheated, all eerily return to their original shape.

When solid, Field’s alloy is very strong and stable and is far stiffer than most shape-memory polymers, according to Zhang. A crucial benefit of the new material is that an object can easily be crushed down into a much smaller spaces for transport or storage before being restored to its usual shape. The researchers think this would make the material ideal for use in space missions, where it could be used to make antennas or building superstructures that could packed tightly on spacecraft ship and then expanded on arrival on the Moon or another planet.

Space cushions

The material could also be used to make cushions because it can absorb a considerable amount of energy when crushed. Zhang suggests that this could be useful for building reusable spacecraft. “Normally, engineers use aluminium or steel to produce cushion structures,” he says. “After you land on the Moon, the metal absorbs the energy and deforms. It’s over – you can use it only once.”

In contrast, a spacecraft with landing cushions built using a liquid metal lattice could be reused over and over again. “Using this Field’s alloy, you can crash into it like other metals, but then heat it up later to recover its shape,” Zhang said.

“There’s been growing interest in machines and structures that can change their shape, stiffness, and ability to bear load. These architectures have potential use in emerging applications like soft robots that mimic biological organisms, wearable computing systems that can conform to the body’s natural motion, or wearable robotics that can assist in human motor tasks,” says Carmel Majidi, a mechanical engineer from the Carnegie Mellon University. “[This work] nicely builds on past research in stiffness tuning and shape memory materials,” he says, adding it. “is an excellent demonstration of how low melting point metals can be used for creating smart and adaptive structures”.

Enormous changes

Michael Dickey —a chemical engineer at North Carolina State University agrees, adding, “This work nicely takes advantage of the capabilities of 3D printing, the elastic energy of elastomers, and the enormous changes in modulus that occur when low melting point metal alloys melt”.

With their initial study complete, the researchers are now working to improve the durability, strength and energy absorption capacity of their liquid metal lattice materials – alongside scaling up and refining the manufacturing process for such.

Zhang also has another goal in mind. “Our dream is to build a liquid metal robot,” he said. “Now we have a hand, so we’re one step further.