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Better material for wearable biosensors

Biosensors that are wearable on human skin or safely used inside the body are increasingly prevalent for both medical applications and everyday health monitoring. Finding the right materials to bind the sensors together and adhere them to surfaces is also an important part of making this technology better. A recent study from Binghamton University, State University of New York offers one possible solution, especially for skin applications.

Matthew S. Brown, a fourth-year PhD student with Assistant Professor Ahyeon Koh’s lab in the Department of Biomedical Engineering, served as the lead author for “Electronic?ECM: A Permeable Microporous Elastomer for an Advanced Bio-Integrated Continuous Sensing Platform,” published in the journal Advanced Materials Technology.

The study utilizes polydimethylsiloxane (PDMS), a silicone material popular for use in biosensors because of its biocompatibility and soft mechanics. It’s generally utilized as a solid film, nonporous material, which can lead to problems in sensor breathability and sweat evaporation.

“In athletic monitoring, if you have a device on your skin, sweat can build up under that device,” Brown said. “That can cause inflammation and also inaccuracies in continuous monitoring applications.

“For instance, one experiment with electrocardiogram (ECG) analysis showed that the porous PDMS allowed for the evaporation of sweat during exercise, capable of maintaining a high-resolution signal. The nonporous PDMS did not provide the ability for the sweat to readily evaporate, leading to a lower signal resolution after exercise.

The team created a porous PDMS material through electrospinning, a production method that makes nanofibers through the use of electric force.

During mechanical testing, the researchers found that this new material acted like the collagen and elastic fibers of the human epidermis. The material was also capable of acting as a dry adhesive for the electronics to strongly laminate on the skin, for adhesive-free monitoring. Biocompatibility and viability testing also showed better results after seven days of use, compared to the nonporous PDMS film.

“You can use this in a wide variety of applications where you need fluids to passively transfer through the material — such as sweat — to readily evaporate through the device,” Brown said.

Because the material’s permeable structure is capable of biofluid, small-molecule and gas diffusion, it can be integrated with soft biological tissue such as skin, neural and cardiac tissue with reduced inflammation at the application site.

Among the applications that Brown sees are electronics for healing long-term, chronic wounds; breathable electronics for oxygen and carbon dioxide respiratory monitoring; devices that integrate human cells within implantable electronic devices; and real-time, in-vitro chemical and biological monitoring.

Koh — whose recent projects include sweat-assisted battery power and biomonitoring — described the porous PDMS study as “a cornerstone of my research.”

“My lab is very interested in developing a biointegrated sensing system beyond wearable electronics,” she said. “At the moment, technologies have advanced to develop durable and flexible devices over the past 10 years. But we always want to go even further, to create sensors that can be used in more nonvisible systems that aren’t just on the skin.

“Koh also sees the possibilities for this porous PDMS material in another line of research she is pursuing with Associate Professor Seokheun Choi from the Department of Electrical and Computer Engineering. She and Choi are combining their strengths to create stretchable papers for soft bioelectronics, enabling us to monitor physiological statuses.

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Materials provided by Binghamton University. Original written by Chris Kocher. Note: Content may be edited for style and length.

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Quantum light squeezes the noise out of microscopy signals

Researchers at the Department of Energy’s Oak Ridge National Laboratory used quantum optics to advance state-of-the-art microscopy and illuminate a path to detecting material properties with greater sensitivity than is possible with traditional tools.

“We showed how to use squeezed light — a workhorse of quantum information science — as a practical resource for microscopy,” said Ben Lawrie of ORNL’s Materials Science and Technology Division, who led the research with Raphael Pooser of ORNL’s Computational Sciences and Engineering Division. “We measured the displacement of an atomic force microscope microcantilever with sensitivity better than the standard quantum limit.”

Unlike today’s classical microscopes, Pooser and Lawrie’s quantum microscope requires quantum theory to describe its sensitivity. The nonlinear amplifiers in ORNL’s microscope generate a special quantum light source known as squeezed light.

“Imagine a blurry picture,” Pooser said. “It’s noisy and some fine details are hidden. Classical, noisy light prevents you from seeing those details. A ‘squeezed’ version is less blurry and reveals fine details that we couldn’t see before because of the noise.” He added, “We can use a squeezed light source instead of a laser to reduce the noise in our sensor readout.”

The microcantilever of an atomic force microscope is a miniature diving board that methodically scans a sample and bends when it senses physical changes. With student interns Nick Savino, Emma Batson, Jeff Garcia and Jacob Beckey, Lawrie and Pooser showed that the quantum microscope they invented could measure the displacement of a microcantilever with 50% better sensitivity than is classically possible. For one-second long measurements, the quantum-enhanced sensitivity was 1.7 femtometers — about twice the diameter of a carbon nucleus.

“Squeezed light sources have been used to provide quantum-enhanced sensitivity for the detection of gravitational waves generated by black hole mergers,” Pooser said. “Our work is helping to translate these quantum sensors from the cosmological scale to the nanoscale.”

Their approach to quantum microscopy relies on control of waves of light. When waves combine, they can interfere constructively, meaning the amplitudes of peaks add to make the resulting wave bigger. Or they can interfere destructively, meaning trough amplitudes subtract from peak amplitudes to make the resulting wave smaller. This effect can be seen in waves in a pond or in an electromagnetic wave of light like a laser.

“Interferometers split and then mix two light beams to measure small changes in phase that affect the interference of the two beams when they are recombined,” Lawrie said. “We employed nonlinear interferometers, which use nonlinear optical amplifiers to do the splitting and mixing to achieve classically inaccessible sensitivity.”

The interdisciplinary study, which is published in Physical Review Letters, is the first practical application of nonlinear interferometry.

A well-known aspect of quantum mechanics, the Heisenberg uncertainty principle, makes it impossible to define both the position and momentum of a particle with absolute certainty. A similar uncertainty relationship exists for the amplitude and phase of light.

That fact creates a problem for sensors that rely on classical light sources like lasers: The highest sensitivity they can achieve minimizes the Heisenberg uncertainty relationship with equal uncertainty in each variable. Squeezed light sources reduce the uncertainty in one variable while increasing the uncertainty in the other variable, thus “squeezing” the uncertainty distribution. For that reason, the scientific community has used squeezing to study phenomena both great and small.

The sensitivity in such quantum sensors is typically limited by optical losses. “Squeezed states are fragile quantum states,” Pooser said. “In this experiment, we were able to circumvent the problem by exploiting properties of entanglement.” Entanglement means independent objects behaving as one. Einstein called it “spooky action at a distance.” In this case, the intensities of the light beams are correlated with each other at the quantum level.

“Because of entanglement, if we measure the power of one beam of light, it would allow us to predict the power of the other one without measuring it,” he continued. “Because of entanglement, these measurements are less noisy, and that provides us with a higher signal to noise ratio.”

ORNL’s approach to quantum microscopy is broadly relevant to any optimized sensor that conventionally uses lasers for signal readout. “For instance, conventional interferometers could be replaced by nonlinear interferometry to achieve quantum-enhanced sensitivity for biochemical sensing, dark matter detection or the characterization of magnetic properties of materials,” Lawrie said.

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How to have a blast like a black hole

Laser Engineering at Osaka University have successfully used short, but extremely powerful laser blasts to generate magnetic field reconnection inside a plasma. This work may lead to a more complete theory of X-ray emission from astronomical objects like black holes.

In addition to being subjected to extreme gravitational forces, matter being devoured by a black hole can be also be pummeled by intense heat and magnetic fields. Plasmas, a fourth state of matter hotter than solids, liquids, or gasses, are made of electrically charged protons and electrons that have too much energy to form neutral atoms. Instead, they bounce frantically in response to magnetic fields. Within a plasma, magnetic reconnection is a process in which twisted magnetic field lines suddenly “snap” and cancel each other, resulting in the rapid conversion of magnetic energy into particle kinetic energy. In stars, including our sun, reconnection is responsible for much of the coronal activity, such as solar flares. Owing to the strong acceleration, the charged particles in the black hole’s accretion disk emit their own light, usually in the X-ray region of the spectrum.

To better understand the process that gives rise to the observed X-rays coming from black holes, scientists at Osaka University used intense laser pulses to create similarly extreme conditions on the lab. “We were able to study the high-energy acceleration of electrons and protons as the result of relativistic magnetic reconnection,” Senior author Shinsuke Fujioka says. “For example, the origin of emission from the famous black hole Cygnus X-1, can be better understood.”

This level of light intensity is not easily obtained, however. For a brief instant, the laser required two petawatts of power, equivalent to one thousand times the electric consumption of the entire globe. With the LFEX laser, the team was able to achieve peak magnetic fields with a mind-boggling 2,000 telsas. For comparison, the magnetic fields generated by an MRI machine to produce diagnostic images are typically around 3 teslas, and Earth’s magnetic field is a paltry 0.00005 teslas. The particles of the plasma become accelerated to such an extreme degree that relativistic effects needed to be considered.

“Previously, relativistic magnetic reconnection could only be studied via numerical simulation on a supercomputer. Now, it is an experimental reality in a laboratory with powerful lasers,” first author King Fai Farley Law says. The researchers believe that this project will help elucidate the astrophysical processes that can happen at places in the Universe that contain extreme magnetic fields.

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New X-ray detection technology developed

Florida State University researchers have developed a new material that could be used to make flexible X-ray detectors that are less harmful to the environment and cost less than existing technologies.

The team led by Biwu Ma, a professor in the Department of Chemistry and Biochemistry, created X-ray scintillators that use an environmentally friendly material. Their research was published in the journal Nature Communications .

“Developing low-cost scintillation materials that can be easily manufactured and that perform well remains a great challenge,” Ma said. “This work paves the way for exploring new approaches to create these important devices.”

Biwu Ma, professor in the Department of Chemistry and Biochemistry X-ray scintillators convert the radiation of an X-ray into visible light, and they are a common type of X-ray detector. When you visit the dentist or the airport, scintillators are used to take images of your teeth or scan your luggage.

Various materials have been used to make X-ray scintillators, but they can be difficult or expensive to manufacture. Some recent developments use compounds that include lead, but the toxicity of lead could be a concern.

Ma’s team found a different solution. They used the compound organic manganese halide to create scintillators that don’t use lead or heavy metals. The compound can be used to make a powder that performs very well for imaging and can be combined with a polymer to create a flexible composite that can be used as a scintillator. That flexibility broadens the potential use of this technology.

“Researchers have made scintillators with a variety of compounds, but this technology offers something that combines low cost with high performance and environmentally friendly materials,” Ma said. “When you also consider the ability to make flexible scintillators, it’s a promising avenue to explore.”

Ma recently received a GAP Commercialization Investment Program grant from the FSU Office of the Vice President for Research to develop this technology. The grants help faculty members turn their research into possible commercial products.

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Materials provided by Florida State University. Original written by Bill Wellock. Note: Content may be edited for style and length.

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Don’t forget to clean robotic support pets, study says

Robotic support pets used to reduce depression in older adults and people with dementia acquire bacteria over time, but a simple cleaning procedure can help them from spreading illnesses, according to a new study.

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Studying water polo for kicks

Researchers at the University of Tsukuba used high-speed cameras and pressure sensors to quantify the force created by water polo players during kicking motions. They found that the high efficacy of the “eggbeater” technique exceeds the predictions of conventional biomechanical theories, which may be due to turbulent water flow. This research may help improve our understanding of both the biophysics of sports, as well as lead to new ways to travel through the water more easily.

While polo played with horses may seem genteel and relaxing, the same cannot be said of water polo. It is a grueling competition in which players must constantly expend energy just to stay in a position to catch or throw the ball. A common swimming technique that allows players to tread water while upright is called an “eggbeater” kick, in which the legs make large circles, just like the kitchen gadget. In fact, they spend about half their time in the water performing this motion, which allows players to elevate themselves from the surface without becoming exhausted.

To understand why this method is so efficient, researchers at the University of Tsukuba studied six male water polo players.

“Sports are often a good place to look for highly optimized techniques,” Senior author Professor Hideki Takagi says. “We captured the kicking motions using three high-speed cameras, and we attached four pairs of pressure sensors to the dorsal and plantar surfaces of each participant’s right foot.”

The video recording allowed the scientists to know the position, velocity, and acceleration at each moment of time, and the force could be calculated using the pressure sensors.

Surprisingly, the researchers found that the force created by the eggbeater kick was greater than would be expected if one just applied Newton’s laws and hydrodynamics. “Our study hints that water polo players are actually taking advantage of complex physics, including unstable vortices, to achieve this increased efficiency,” explains Professor Takagi. “In addition to improving sports performance, the results of this research may lead to optimized underwater propulsion.”

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Scientists get atomistic picture of platinum catalyst degradation

Degradation of platinum, used as a key electrode material in the hydrogen economy, severely shortens the lifetime of electrochemical energy conversion devices, such as fuel cells. For the first time, scientists elucidated the movements of the platinum atoms that lead to catalyst surface degradation. Their results are published today in Nature Catalysis.

For more than half a century, platinum has been known as one of the best catalysts for oxygen reduction, one of the key reactions in fuel cells. However, it is difficult to meet the catalysts’ long-term high activity and stability needed for the massive deployment of the hydrogen technology in the transportation sector.

Scientists led by Kiel University (Germany), in collaboration with the ESRF, University of Victoria (Canada), University of Barcelona (Spain) and Forschungszentrum Jülich (Germany), have now found out why and how platinum degrades. “We have come up with an atomistic picture to explain it,” says Olaf Magnussen, professor at Kiel University and corresponding author of the article.

In order to achieve this, the team went to ESRF’s beamline ID31 to study the different facets of platinum electrodes in electrolyte solution. They discovered how atoms arrange themselves and move on the surface during the processes of oxidation, the main reaction responsible for platinum dissolution.

The findings open doors to atomistic engineering: “With this new knowledge, we can imagine targeting certain shapes and surface arrangements of nanoparticles to enhance the stability of the catalyst. We can also find how the atoms move, so we could potentially add surface additives to suppress atoms moving the wrong way,” explains Jakub Drnec, scientist at beamline ID31 and co-author of the study.

The fact that the experiments took place under electrochemical conditions similar to what happens in the actual device was key to translate the findings into fuel cell technology. “Because platinum surface rapidly changes during oxidation, these measurements became possible only thanks to a new, very fast technique for surface structure characterization. This method, high-energy surface X-ray diffraction, has been co-developed at the ESRF” explains Timo Fuchs, from Kiel University and co-author of the study. “And it is, in fact, the only technique that can provide this kind of information in the real environment,” he adds. This is the first publication where atomic movements were determined by the technique under such conditions.

This research owes its success to the combination of the X-ray measurements at the ESRF with highly sensitive dissolution measurements performed at Forschungszentrum Jülich and advanced computer simulations. “Only such a combination of different characterization techniques and theoretical calculations provides a full picture of what goes on with the atoms at the nanoscale level in a platinum catalyst,” notes Federico Calle-Vallejo from University of Barcelona, in charge of the simulations.

The next step for the team is to continue experiments that provide insight into the degradation mechanisms of further model facets mimicking edges and corners on catalyst particles. These results will provide a map of platinum stability under reaction conditions and allow researchers to develop rational strategies for the design of more stable catalysts in the future.

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Contagion model predicts flooding in urban areas

Inspired by the same modeling and mathematical laws used to predict the spread of pandemics, researchers at Texas A&M University have created a model to accurately forecast the spread and recession process of floodwaters in urban road networks. With this new approach, researchers have created a simple and powerful mathematical approach to a complex problem.

“We were inspired by the fact that the spread of epidemics and pandemics in communities has been studied by people in health sciences and epidemiology and other fields, and they have identified some principles and rules that govern the spread process in complex social networks,” said Dr. Ali Mostafavi, associate professor in the Zachry Department of Civil and Environmental Engineering. “So we ask ourselves, are these spreading processes the same for the spread of flooding in cities? We tested that, and surprisingly, we found that the answer is yes.”

The findings of this study were recently published in Nature Scientific Reports.

The contagion model, Susceptible-Exposed-Infected-Recovered (SEIR), is used to mathematically model the spread of infectious diseases. In relation to flooding, Mostafavi and his team integrated the SEIR model with the network spread process in which the probability of flooding of a road segment depends on the degree to which the nearby road segments are flooded.

In the context of flooding, susceptible is a road that can be flooded because it is in a flood plain; exposed is a road that has flooding due to rainwater or overflow from a nearby channel; infected is a road that is flooded and cannot be used; and recovered is a road where the floodwater has receded.

The research team verified the model’s use with high-resolution historical data of road flooding in Harris County during Hurricane Harvey in 2017. The results show that the model can monitor and predict the evolution of flooded roads over time.

“The power of this approach is it offers a simple and powerful mathematical approach and provides great potential to support emergency managers, public officials, residents, first responders and other decision makers for flood forecast in road networks,” Mostafavi said.

The proposed model can achieve decent precision and recall for the spatial spread of the flooded roads.

“If you look at the flood monitoring system of Harris County, it can show you if a channel is overflowing now, but they’re not able to predict anything about the next four hours or next eight hours. Also, the existing flood monitoring systems provide limited information about the propagation of flooding in road networks and the impacts on urban mobility. But our models, and this specific model for the road networks, is robust at predicting the future spread of flooding,” he said. “In addition to flood prediction in urban networks, the findings of this study provide very important insights about the universality of the network spread processes across various social, natural, physical and engineered systems; this is significant for better modeling and managing cities, as complex systems.”

The only limitation to this flood prediction model is that it cannot identify where the initial flooding will begin, but Mostafavi said there are other mechanisms in place such as sensors on flood gauges that can address this.

“As soon as flooding is reported in these areas, we can use our model, which is very simple compared to hydraulic and hydrologic models, to predict the flood propagation in future hours. The forecast of road inundations and mobility disruptions is critical to inform residents to avoid high-risk roadways and to enable emergency managers and responders to optimize relief and rescue in impacted areas based on predicted information about road access and mobility. This forecast could be the difference between life and death during crisis response,” he said.

Civil engineering doctoral student and graduate research assistant Chao Fan led the analysis and modeling of the Hurricane Harvey data, along with Xiangqi (Alex) Jiang, a graduate student in computer science, who works in Mostafavi’s UrbanResilience.AI Lab.

“By doing this research, I realize the power of mathematical models in addressing engineering problems and real-world challenges.

This research expands my research capabilities and will have a long-term impact on my career,” Fan said. “In addition, I am also very excited that my research can contribute to reducing the negative impacts of natural disasters on infrastructure services.”

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Materials provided by Texas A&M University. Original written by Alyson Chapman. Note: Content may be edited for style and length.

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Graphene sensors find subtleties in magnetic fields

Researchers used an ultrathin graphene ‘sandwich’ to create a tiny magnetic field sensor that can operate over a greater temperature range than previous sensors, while also detecting miniscule changes in magnetic fields that might otherwise get lost within a larger magnetic background.

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Contact tracing apps unlikely to contain COVID-19 spread: UK researchers

Contract tracing apps used to reduce the spread of COVID-19 are unlikely to be effective without proper uptake and support from concurrent control measures, finds a new study by UCL researchers.

The systematic review*, published in Lancet Digital Health, shows that evidence around the effectiveness of automated contact tracing systems is currently very limited, and large-scale manual contact tracing alongside other public health control measures — such as physical distancing and closure of indoor spaces such as pubs — is likely to be required in conjunction with automated approaches.

The team found 15 relevant studies by reviewing more than 4,000 papers on automated and partially-automated contact tracing, and analysed these to understand the potential impact these tools could have in controlling the COVID-19 pandemic.

Lead author Dr Isobel Braithwaite (UCL Institute of Health Informatics) said: “Across a number of modelling studies, we found a consistent picture that although automated contact tracing could support manual contact tracing, the systems will require large-scale uptake by the population and strict adherence to quarantine advice by contacts notified to have a significant impact on reducing transmission.”

The authors suggest that even under optimistic assumptions — where 75-80% of UK smartphone owners are using a contact tracing app, and 90-100% of identified potential close contacts initially adhere to quarantine advice — automated contact tracing methods would still need to be used within an integrated public health response to prevent exponential growth of the epidemic.

In total, 4,033 papers published between 1 Jan 2000 and 14 April 2020 were reviewed, which allowed researchers to identify 15 papers with useful data. The seven studies that addressed automated contact tracing directly were modelling studies that all focused on COVID-19. Five studies of partially-automated contact tracing were descriptive observational studies or case studies, and three studies of automated contact detection looked at a similar disease context to COVID-19, but did not include subsequent tracing or contact notification.

Partially-automated systems may have some automated processes, for instance in determining the duration of follow-up of contacts required, but do not use proximity of smartphones as a proxy for contact with an infected person.

Analysis of automated contact tracing apps generally suggested that high population uptake of relevant apps is required alongside other control measures, while partially-automated systems often had better follow-up and slightly more timely intervention.

Dr Braithwaite said: “Although automated contact tracing shows some promise in helping reduce transmission of COVID-19 within communities, our research highlighted the urgent need for further evaluation of these apps within public health practice, as none of the studies we found provided real-world evidence of their effectiveness, and to improve our understanding of how they could support manual contact tracing systems.”

The review shows that, at present, there is insufficient evidence to justify reliance on automated contact tracing approaches without additional extensive public health control measures.

Dr Robert Aldridge (UCL Institute of Health Informatics) added: “We currently do not have good evidence about whether a notification from a smartphone app is as effective in breaking chains of transmission by giving advice to isolate due to contact with a case of COVID-19 when compared to advice provided by a public health contact tracer. We urgently need to study this evidence gap and examine how automated approaches can be integrated with existing contact tracing and disease control strategies, and generate evidence on whether these new digital approaches are cost-effective and equitable.”

If implemented effectively and quarantine advice is adhered to appropriately, automated contact tracing may offer benefits such as reducing reliance on human recall of close contacts, which could enable identification of additional at-risk individuals, informing potentially affected people in real-time, and saving on resources.

Dr Braithwaite added: “We should be mindful that automated approaches raise potential privacy and ethics concerns, and also rely on high smartphone ownership, so they may be of very limited value in some countries. Too much reliance on automated contact tracing apps may also increase the risk of COVID-19 for vulnerable and digitally-excluded groups such as older people and people experiencing homelessness.”

If implementing automated contact tracing technology, the authors say that decision-makers should thoroughly assess available evidence around its effectiveness, privacy and equality considerations, monitoring this as the evidence base evolves.

They add that plans to properly integrate contact tracing apps within comprehensive outbreak response strategies are important, and their impacts should be evaluated rigorously. A combination of different approaches is needed to control COVID-19, and the review concludes that contact tracing apps have the potential to support that but they are not a panacea.

This study is co-authored by researchers UCL Public Health Data Science Research Group, Institute of Health Informatics, Department of Applied Health Research, and Collaborative Centre for Inclusion Health.

*A systematic review carefully identifies all the relevant published and unpublished studies, rates them for quality and synthesises the studies’ findings across the studies identified.

Study limitations

As part of this systematic review, researchers did not find any epidemiological studies comparing automated to manual contact tracing systems and their effectiveness in identifying contacts. Other limitations include the lack of eligible empirical studies of fully-automated contact tracing and a paucity of evidence related to ethical concerns or cost-effectiveness.

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