Speaker: Jurgen van Peer | Company: Nanogate | Date: 11-12 May 2021 | Full Presentation Digital printing has clearly established itself for graphics printing, thanks to the advantages it offers over traditional processes like screen printing. More recently, digital printing started morphing into digital manufacturing and also Printed Electronics is taking advantage of that evolution. In this talk we will review Agfa's digital conductive inks based on nanomaterials, and highlight some features of newly developed inks. In the second part of the talk, Nanogate Netherlands will discuss the application of additive digital manufacturing in motor sport products. Join TechBlick on an annual pass to join all live online conference or online version of onsite conference access library of on-demand talks (600 talks + PDFs) portfolio of expert led masterclass year-round platform https://www.techblick.com/ And do NOT miss our flagship event in Berlin on 17-18 OCT 2023 focused on Reshaping the Future of Electronics. This event attracts 550-600 participants from all the world and offers a superb ambience and dynamic exhibition floor. To learn more visit https://www.techblick.com/electronicsreshaped To see feedback about previous event see https://www.techblick.com/events-agenda

A team of engineers at the University of South Florida has invented a new technology that could forever change the manufacturing of wearable, electronic sensors. They’ve figured out a way to speed up production without having to use polymer binders – the industry standard in printing flexible sensors, which are often used to monitor vital signs in health care settings. Their technology "Corona-Enabled Electrostatic Printing for Ultra-Fast R2R Manufacturing of Binder-Free Multifunctional E-Skins", featured on the cover of the journal ACS Applied Materials & Interfaces, prints electronic skin, or “e-skin,” by using corona discharge to create a strong electric field between binder-free functional powders, such as graphene, and flexible, non-conductive surfaces, such as medical tape. The electrostatic force used in Corona-Enabled Electrostatic Printing enables a multitude of e-skin sensors to be printed within sub-seconds, compared to the 20 minutes it takes with polymer binders and doesn’t require heat. E-skin is a micrometer-thin, pliable technology that can be used to measure things such as strain, temperature, and sound. Ying Zhong, assistant professor of mechanical engineering at USF, and her collaborator, Long Wang at California Polytechnic State University, found that the printing technique has broad applications, such as in health monitoring, prosthetics, and robotics. Unlike with polymer binders, there aren’t sizing limitations, making the technique a strong candidate for the roll-to-roll manufacturing of large flexible sensors, which can greatly reduce production costs. “As a new, advanced manufacturing strategy, Corona-Enabled Electrostatic Printing will potentially transform the cost structure for large-area and high-performance electronics and enable versatile applications of flexible, functional systems,” Zhong said. “The technique can help contribute to maintaining the U.S.’s leadership in advanced manufacturing.” Zhong recently received a $308,928 grant from the National Science Foundation to advance her research, proving the patent-pending ultra-fast manufacturing technique can be used to print materials beyond multifunctional e-skin. For more information: https://www.usf.edu/news/2021/usf-engineers-invent-ultra-fast-manufacturing-technology.aspx

In 2017, Green Bay Packers quarterback Aaron Rodgers broke his right collarbone in a game against the Minnesota Vikings. Typically, it takes about 12 weeks for a collarbone to fully heal, but by mid-December fans and commentators were hoping the three-time MVP might recover early and save a losing season. So did Xudong Wang, a professor of materials science and engineering at the University of Wisconsin–Madison and an expert in creating thin, movement-powered medical devices. “I started wondering if we could provide a new solution to bring athletes back to the field quicker than ever,” Wang says. The researchers published the paper " An implantable and bioresorbable electrostimulation device with its own power supply for the healing of bone fractures with biofeedback" in PNAS. Researchers know that electricity can help speed up bone healing, but “zapping” fractures has never really caught on since it requires surgically implanting and removing electrodes powered by an external source. A major update of that same electrostimulation concept, Wang’s latest invention didn’t come in time to help the 2017 Packers — however, it may help many others by making electrostimulation a much more convenient option to speed up bone healing. His thin, flexible device is self-powered, implantable, and bioresorbable, so once the bone is knitted back together, the device’s components dissolve within the body. Bone is a piezoelectric material, meaning it produces a tiny bit of electricity when placed under strain. These jolts of electricity stimulate factors that promote bone growth and healing, which is why electrostimulation is an effective therapy. While there are external stimulators that create an electric field to accelerate healing indirectly, the ideal solution is stimulating the bone directly. Putting the device inside the body, however, has unique requirements — not the least of which is powering it, according to Wang. “The ideal case is to have the device be self-generating, which was something that didn’t exist before this,” he says. To create the new fracture electrostimulation device, or FED, Wang and his team started with a triboelectric nanogenerator, a thin-film device with microstructured surfaces that converts mechanical energy produced by tiny movements into electric power. They coupled the nanogenerator with a pair of electrodes to distribute the electric field to the bone. They built these ultrathin, biodegradable, and bioresorbable components on a substrate of poly(lactic-co-glycolic acid), a commonly used FDA-approved biocompatible polymer. The researchers’ initial tests confirmed that small movements of the device did indeed create an electrical stimulation of about 4 volts, which it could sustain for over six weeks. They then tested the device on rats. The animals implanted with the device completely recovered from a tibia fracture in about six weeks, much more quickly than animals in a control group. The mineral density and flexural strength of the healed bones also reached the same level as healthy bones in the animals that received the electrostimulation. After the treatment, the devices degraded and absorbed into the rats’ bodies with no complications and no need for surgical removal. Wang says that it’s possible to fine-tune how long the stimulator will last within the body — from weeks to months — by tweaking the properties of the bioresorbable material coating the device. Eventually, Wang would like to scale up the fracture electrostimulation device so it will work in humans. But for these self-powered devices, the energy source can be a factor. “Typically, when someone has a broken bone, they need to restrict their movement,” he explains. In other words, someone wearing a cast might not produce enough mechanical energy to power the triboelectric nanogenerator. “The way a rat move provides constant stimulation for the device, but for a broken bone in a human that can’t be moved, that’s an issue,” says Wang. However, the human body provides virtually endless sources of movement that could power the fracture electrostimulation device if the broken bone must remain immobile. “We may need the device to respond to other types of internal mechanical sources, like blood pressure changes,” says Wang, who’s already looking to the FED’s future. “It will be very interesting and impactful to address the development from animal to human,” he says. For more information, visit: https://news.wisc.edu/self-powered-implantable-device-stimulates-fast-bone-healing-then-disappears-without-a-trace/

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Some people are born with hearing loss, while others acquire it with age, infections, or long-term noise exposures. In many instances, the tiny hairs in the inner ear’s cochlea that allow the brain to recognize electrical pulses as sound are damaged. As a step toward an advanced artificial cochlea, researchers in ACS Nano report a conductive membrane, which translated sound waves into matching electrical signals when implanted inside a model ear, without requiring external power. The paper "Acoustic Core-Shell Resonance Harvester for Application of Artificial Cochlea Based on the Piezo-Triboelectric Effect" is published in ACS NANO. When the hair cells inside the inner ear stop working, there’s no way to reverse the damage. Currently, treatment is limited to hearing aids or cochlear implants. But these devices require external power sources and can have difficulty amplifying speech correctly so that it’s understood by the user. One possible solution is to simulate healthy cochlear hairs, converting noise into the electrical signals processed by the brain as recognizable sounds. To accomplish this, previous researchers have tried self-powered piezoelectric materials, which become charged when they’re compressed by the pressure that accompanies sound waves, and triboelectric materials, which produce friction and static electricity when moved by these waves. However, the devices aren’t easy to make and don’t produce enough signals across the frequencies involved in human speech. So, Yunming Wang and colleagues wanted a simple way to fabricate a material that used both compression and friction for an acoustic sensing device with high efficiency and sensitivity across a broad range of audio frequencies. To create a piezo-triboelectric material, the researchers mixed barium titanate nanoparticles coated with silicon dioxide into a conductive polymer, which they dried into a thin, flexible film. Next, they removed the silicon dioxide shells with an alkaline solution. This step left behind a sponge-like membrane with spaces around the nanoparticles, allowing them to jostle around when hit by sound waves. In tests, the researchers showed that contact between the nanoparticles and polymer increased the membrane’s electrical output by 55% compared to the pristine polymer. When they sandwiched the membrane between two thin metal grids, the acoustic sensing device produced a maximum electrical signal at 170 hertz, a frequency within the range of most adults’ voices. Finally, the researchers implanted the device inside a model ear and played a music file. They recorded the electrical output and converted it into a new audio file, which displayed a strong similarity to the original version. The researchers say their self-powered device is sensitive to the wide acoustic range needed to hear most sounds and voices. For more information, visit: https://www.acs.org/content/acs/en/pressroom/presspacs/2021/acs-presspac-october-27-2021/flexible-device-could-treat-hearing-loss-without-batteries.html

Researchers at North Carolina State University demonstrated a low-cost technique for retrieving nanowires from electronic devices that have reached the end of their utility and then using those nanowires in new devices. The work is a step toward more sustainable electronics. The paper, “Recycling of Nanowire Percolation Network for Sustainable Soft Electronics,” is published in the journal Advanced Electronic Materials. “There is a lot of interest in recycling electronic materials because we want to both reduce electronic waste and maximize the use we get out of rare or costly materials,” says Yuxuan Liu, first author of a paper on the work and a Ph.D. student at NC State. “We’ve demonstrated an approach that allows us to recycle nanowires, and that we think could be extended to other nanomaterials – including nanomaterials containing noble and rare-earth elements.” “Our recycling technique differs from conventional recycling,” says Yong Zhu, corresponding author of the paper and the Andrew A. Adams Distinguished Professor of Mechanical and Aerospace Engineering at NC State. “When you think about recycling a glass bottle, it is completely melted down before being used to create another glass object. In our approach, a silver nanowire network is separated from the rest of the materials in a device. That network is then disassembled into a collection of separate silver nanowires in solution. These nanowires can then be used to create a new network and incorporated into a new sensor or other devices.” The new recycling technique takes into account the entire life cycle of a device. The first step is to design devices using polymers that are soluble in solvents that will not also dissolve the nanowires. Once a device has been used, the polymer matrix containing the silver nanowires is dissolved, leaving behind the nanowire network. The network is then placed in a separate solvent and hit with ultrasound. This disperses the nanowires, separating them out of the network. In a proof-of-concept demonstration, the researchers created a wearable health sensor patch that could be used to track a patient’s temperature and hydration. The sensor consisted of silver nanowire networks embedded in a polymer material. The researchers tested the sensors to ensure that they were fully functional. Once used, a sensor patch is normally discarded. But for their demonstration, the researchers dissolved the polymer in water, removed the nanowire network, broke it down into a collection of individual nanowires, and then used those nanowires to create a brand-new wearable sensor. While there was minor degradation in the properties of the nanowire network after each “life cycle,” the researchers found that the nanowires could be recycled four times without harming the sensor’s performance. After four life cycles, you can improve the performance of the nanowire network by introducing new silver nanowires into the mix. “Using our approach, you get far more use from the nanowires,” Zhu says. “And even after the nanowires have broken down many times, to the point where they can’t be reused, we can still use them as feedstock for conventional recycling. It’s a tremendous reduction in waste.” One key to the recycling process is identifying a solvent with a low surface tension for use in breaking up the nanowire network. “Low surface tension is important because it makes it easier for the solvent to diffuse into the narrow junctions between nanowires in the network, facilitating the disassembling of the network,” Liu says. The researchers found that it is also important to find the right balance of time when breaking up the nanowire networks with ultrasound. If you apply the ultrasound for too long, you can break the nanowires. If you don’t apply the ultrasound for long enough, you can end up with clumps of nanowires. “The approach we’ve demonstrated here could be used to recycle other nanomaterials – such as nanoparticles, carbon nanotubes, other types of nanowires, and two-dimensional materials – as long as they are used in the form of a network,” Zhu says. For more information, visit: https://news.ncsu.edu/2021/07/recycling-nanowires-in-electronics/

Researchers at North Carolina State University have created a soft and stretchable device that converts movement into electricity and can work in wet environments. The paper, “A Soft Variable-Area Electrical-Double-Layer Energy Harvester,” is published in the journal Advanced Materials. “Mechanical energy – such as the kinetic energy of wind, waves, body movement, and vibrations from motors – is abundant,” says Michael Dickey, corresponding author of a paper on the work and Camille & Henry Dreyfus Professor of Chemical and Biomolecular Engineering at NC State. “We have created a device that can turn this type of mechanical motion into electricity. And one of its remarkable attributes is that it works perfectly well underwater.” The heart of the energy harvester is a liquid metal alloy of gallium and indium. The alloy is encased in a hydrogel – a soft, elastic polymer swollen with water. The water in the hydrogel contains dissolved salts called ions. The ions assemble at the surface of the metal, which can induce a charge in the metal. Increasing the area of the metal provides more surface to attract a charge. This generates electricity, which is captured by a wire attached to the device. “Since the device is soft, any mechanical motion can cause it to deform, including squishing, stretching, and twisting,” Dickey says. “This makes it versatile for harvesting mechanical energy. For example, the hydrogel is elastic enough to be stretched to five times its original length.” In experiments, researchers found that deforming the device by only a few millimeters generates a power density of approximately 0.5 mW m-2. This amount of electricity is comparable to several popular classes of energy harvesting technologies. “However, other technologies don’t work well, if at all, in wet environments,” Dickey says. “This unique feature may enable applications from biomedical settings to athletic wear to marine environments. Plus, the device is simple to make. “There is a path to increase the power, so we consider the work we described here a proof-of-concept demonstration.” The researchers already have two related projects underway. One project is aimed at using the technology to power wearable devices by increasing the harvester’s power output. The second project evaluates how this technology could be used to harvest wave power from the ocean. For more information, visit: https://news.ncsu.edu/2021/08/liquid-metal-energy-harvester/

As anyone who has ever parked a car in the sun on a hot summer day knows, glass windows are great at letting sunlight in but terrible at allowing heat out. Now, engineers at Duke University have developed smart window-like technology that, with the flip of a switch, can alternate between harvesting heat from sunlight and allowing an object to cool. The approach could be a boon for HVAC savings, potentially cutting energy usage by nearly 20% in the United States alone. The electrochromic technology – material that changes color or opacity when electricity is applied – is detailed in a paper "Ultra-Wideband Transparent Conductive Electrode for Electrochromic Synergistic Solar and Radiative Heat Management" published in the journal American Chemical Society Energy Letters. “We have demonstrated the very first electrochromic device that can switch between solar heating and radiative cooling,” said Po-Chun Hsu, assistant professor of mechanical engineering and materials science at Duke. “Our electrochromic tuning method does not have any moving parts and is continuously tunable.” Smart windows made from electrochromic glass are a relatively new technology that uses an electrochromic reaction to change glass from transparent to opaque and back again in the blink of an eye. While there are many approaches to creating this phenomenon, they all involve sandwiching an electrically responsive material between two thin layers of electrodes and passing an electric current between them. While this trick is difficult enough to achieve for visible light, it becomes even more so when having to also consider mid-infrared light (radiative heat). In the paper, Hsu and his graduate student Chenxi Sui demonstrate a thin device that interacts with both spectrums of light while switching between passive heating and cooling modes. In the heating mode, the device darkens to absorb sunlight and stop mid-infrared light from escaping. In the cooling mode, the darkened window-like layer clears, simultaneously revealing a mirror that reflects sunlight and allows mid-infrared light from behind the device to dissipate. Because the mirror is never transparent to visible light, the device would not replace windows in homes or offices, but it might be used on other building surfaces. “It’s very difficult to create materials that can function in both of these regimes,” Hsu said. “Our device has one of the largest tuning ranges in thermal radiation ever demonstrated.” There were two major challenges to overcome to engineer such a device. The first was creating electrode layers that conduct electricity and are transparent to both visible light and thermal radiation. Most conductive materials such as metals, graphite, and some oxides don’t fit the bill, as these two properties are at odds with one another, so Hsu and Sui engineered their own. The researchers started with a one-atom-thick layer of graphene, which they showed is too thin to reflect or absorb either type of light. But it is also not conducive enough to transmit the amount of electricity required for the device to work at a large scale. To get around this limitation, Hsu and Sui added a thin grid of gold on top of the graphene to act as a highway for electricity. While this somewhat decreased the graphene’s ability to allow light to pass through unimpeded, the tradeoff was small enough to be worth it. The second challenge involved engineering a material that could go between the two electrode layers and switch back and forth between absorbing light and heat or allowing them to pass through. The researchers achieved this by harnessing a phenomenon called plasmonics. When tiny, nanoscale metal particles are placed just nanometers away from each other, they can essentially trap specific wavelengths of light based on their size and spacing. But in this case, the nanoparticles are randomly distributed in clusters, leading to interactions with a wide range of wavelengths, which is beneficial for efficiently trapping sunlight. In the demonstration, electricity passing through the two electrodes causes metal nanoparticles to form near the top electrode. Not only does this blackout the device, but it also causes the entire device to absorb and trap both visible light and heat. And when the electrical flow is reversed, the nanoparticles dissolve back into the liquid transparent electrolyte. The transition between the two states takes a minute or two to complete. “The device would spend many hours in one state or the other out in the real world, so losing a couple of minutes of efficiency during the transition is just a drop in the bucket,” said Hsu. There are still many challenges to making this technology useful in everyday settings. The largest might be increasing the number of times the nanoparticles can cycle between forming and disintegrating, as the prototype was only able to perform a couple dozen transitions before losing efficiency. There is also room for improvement in the solar reflectivity of the cooling mode, which Hsu hopes can achieve sub-ambient cooling in the near future. As the technology matures, however, there may be many applications for it. The technology might be applied to exterior walls or roofs to help heat and cool buildings while consuming very little energy. Providing the building envelopes such a dynamic capability to use renewable resources for heating and cooling could also open up the opportunity to use less of the construction materials that have been a significant source of carbon emission for decades. For more information, visit: https://pratt.duke.edu/about/news/smart-material-switches-between-heating-and-cooling-minutes

Speaker: Frank Louwet | Company: Agfa | Date: 11-12 May 2021 | Full Presentation Digital printing has clearly established itself for graphics printing, thanks to the advantages it offers over traditional processes like screen printing. More recently, digital printing started morphing into digital manufacturing and also Printed Electronics is taking advantage of that evolution. In this talk we will review Agfa's digital conductive inks based on nanomaterials, and highlight some features of newly developed inks. In the second part of the talk, Nanogate Netherlands will discuss the application of additive digital manufacturing in motor sport products. Peter Willaert Global Marketing Manager Printed Electronics @ Agfa Bio Experienced Product Marketing and Business Development Manager in Printed Electronics with a background in Electronic Engineering. Over the years I have developed a broad knowledge about materials and processes for applications like RFID, iOT, Sensors, Displays etc. Join TechBlick on an annual pass to join all live online conference or online version of onsite conference access library of on-demand talks (600 talks + PDFs) portfolio of expert led masterclass year-round platform https://www.techblick.com/ And do NOT miss our flagship event in Berlin on 17-18 OCT 2023 focused on Reshaping the Future of Electronics. This event attracts 550-600 participants from all the world and offers a superb ambience and dynamic exhibition floor. To learn more visit https://www.techblick.com/electronicsreshaped To see feedback about previous event see https://www.techblick.com/events-agenda

Miniaturized electronics, minute sample volumes in lab equipment, small footprint batteries, and a multitude of other applications have one thing in common: The need for miniaturization and component flexibility. Whether employed as a reference sensor for precise ambient temperature measurement, or for temperature monitoring of critical components – the tiny sensor ‘microRTD’ developed by Heraeus Nexensos fulfills the need for a tiny, flexible temperature sensor. Thanks to a well-focused development effort, the sensor is ready for the transition to pilot plant production. The microRTD—the Right Temperature Sensor for Applications Requiring Ultrasmall, Ultra-Thin, and Flexibility With a footprint of just 0.6mm x 0.3 mm and a low profile of 50 microns, the microRTD can be employed in applications that require temperature control on localized hot spots or require a reference sensor that contributes to the overall small system layout. As a result of the low profile and innovative production technology, the bendable microRTD sensor is capable of conformal contact to curved or flexible surfaces, resulting in fast and precise temperature detection. The operating temperature window is -40 to +140 °C. Miniaturization Combined with Precision – Ready for Pilot Evaluation by Our Customers In close cooperation with a strategic partner, Nexensos channeled decades of sensor expertise into the development of the miniaturized temperature sensor. In the next phase, a large-scale production facility will be constructed, ready to serve our customer’s needs. With this next exciting stage, Nexensos ensures that the required production capabilities will be in place to fill our customers’ requirements for this innovative sensor. For more information: https://www.heraeus.com/en/hne/company_sensors/press_news_sensors/2021_news_hne/2021-08-micrortd.html?utm_medium=social.post&utm_source=linkedin&utm_campaign=HNE.micro-rtd&utm_content=option4

Graphene, hexagonally arranged carbon atoms in a single layer with, superior pliability and high conductivity, could advance flexible electronics according to a Penn State-led international research team. Huanyu “Larry” Cheng, Dorothy Quiggle Career Development Professor in Penn State's Department of Engineering Science and Mechanics (ESM), heads the collaboration, which recently published two studies that could inform research and development of future motion detection, tactile sensing and health monitoring devices. Investigating how laser processing affects graphene form and function Several substances can be converted into carbon to create graphene through laser radiation. Called laser-induced graphene (LIG), the resulting product can have specific properties determined by the original material. The team tested this process and their results were made available online ahead of publication in SCIENCE CHINA Technological Sciences "Effects of laser processing parameters on properties of laser-induced graphene by irradiating CO2 laser on polyimide". Samples of polyimide, a type of plastic, were irradiated through laser scanning. The researchers varied the power, scanning speed, number of passes, and density of scanning lines. “We wanted to look at how different parameters of the laser processing process create different nanostructures,” Cheng said. “Varying the power allowed us to create LIG either in a fiber or foam structure.” The researchers found that lower power levels, from 7.2 watts to roughly 9 watts, resulted in the formation of a porous foam with many ultrafine layers. This LIG foam exhibited electrical conductivity and fair resistance to heat damage — both properties that are useful in components of electronic devices. Increasing the power from approximately 9 watts to 12.6 watts changed the LIG formation pattern from foam to bundles of small fibers. These bundles grew larger in diameter with increased laser power, while higher power promoted the web-like growth of a fiber network. The fibrous structure showed better electrical conductivity than the foam. According to Cheng, this increased performance combined with the fiber’s form could open possibilities for sensing devices. “In general, this is a conductive framework we can use to construct other components,” Cheng said. “As long as the fiber is conductive, we can use it as a scaffold and do a lot of subsequent modifications on the surface to enable a number of sensors, such as a glucose sensor on the skin or an infection detector for wounds.”Varying the laser scanning speed, density, and passes for the LIG formed at different powers also influenced conductivity and subsequent performance. More laser exposure resulted in higher conductivity but eventually dropped due to excess carbonization from burning. Demonstrating a low-cost LIG sensor Using the previous study as a foundation, Cheng and the team set out to design, fabricate and test a flexible LIG pressure sensor. “Pressure sensors are very important,” Cheng said. “We can use them not only in households and manufacturing but also on the skin surface to measure lots of signals from the human body, like the pulse. They can also be used at the human-machine interface to enhance the performance of prosthetic limbs or monitor their attachment points.” The team tested two designs. For the first, they sandwiched a thin LIG foam layer between two polyimide layers containing copper electrodes. When the pressure was applied, the LIG generated electricity. The voids in the foam reduced the number of pathways for electricity to travel, making it easier to localize the pressure source, and appeared to improve sensitivity to delicate touches. This first design, when attached to the back of the hand or the finger, detected bending and stretching hand movements — as well as the characteristic percussion, tidal and diastolic waves of the heartbeat. According to Cheng, this pulse reading could be combined with an electrocardiogram reading to yield blood pressure measurements without a cuff. In the second design, the researchers incorporated nanoparticles into the LIG foam. These tiny spheres of molybdenum disulfide, a semiconductor that can act as a conductor and an insulator, enhanced the foam’s sensitivity and resistance to physical forces. This design was also resilient to repeated use, showing nearly identical performance before and after nearly 10,000 uses. Both designs were cost-effective and allowed for simple data acquisition, according to Cheng. For more information: https://www.psu.edu/news/research/story/graphene-made-lasers-wearable-health-devices/

Noninvasive glucose monitoring devices are not currently commercially available in the United States, so people with diabetes must collect blood samples or use sensors embedded under the skin to measure their blood sugar levels. Now, with a new wearable device created by Penn State researchers, less intrusive glucose monitoring could become the norm. Led by Huanyu “Larry” Cheng, Dorothy Quiggle Career Development Professor in Penn State's Department of Engineering Science and Mechanics, the researchers published the details of the noninvasive, low-cost sensor that can detect glucose in sweat in Biosensors and Bioelectronics "Laser-induced graphene non-enzymatic glucose sensors for on-body measurements". The researchers constructed the device first with laser-induced graphene (LIG), a material consisting of atom-thick carbon layers in various shapes. With high electrical conductivity and a convenient fabrication time of just seconds, LIG appeared to be an ideal framework for the sensing device but there was a significant caveat. “The challenge here is that LIG is not sensitive to glucose at all,” Cheng said. “So, we needed to deposit a glucose-sensitive material onto the LIG.” The team chose nickel because of its robust glucose sensitivity, according to Cheng, and combined it with gold to lower potential risks of an allergic reaction. The researchers hypothesized that the LIG outfitted with the nickel-gold alloy would be able to detect low concentrations of glucose in sweat on the skin’s surface. A material with high glucose sensitivity was a priority. Sweat exhibits remarkably low glucose concentrations compared to blood but, according to Cheng, there is a strong correlation between glucose levels in sweat and blood. While the concentration of glucose in sweat is about 100 times less than the concentration in blood, the team’s device is sensitive enough to accurately measure the glucose in sweat and reflect the concentration in blood. The nickel-gold alloy’s sensitivity allowed Cheng’s team to exclude enzymes, which are often used to measure glucose in more invasive, commercially available devices or in noninvasive monitors proposed by other researchers. These enzymes, however, can degrade quickly with time and changing temperatures. “An enzymatic sensor has to be kept at a certain temperature and pH, and the enzyme can’t be stored in the long term,” Cheng said. “A nonenzymatic glucose sensor, on the other hand, is advantageous in terms of stable performance and glucose sensitivity regardless of these changes.” Nonenzymatic sensors require an alkaline solution, which can damage the skin and typically limits device wearability. To curb this issue, Cheng and his team attached a microfluidic chamber to the LIG alloy. This chamber is smaller than previously developed configurations to promote wearability and porous to allow for a range of movement, such as stretching or crushing. It is connected to a collection inlet that passes sweat into the solution without allowing the solution to touch the skin. The basic solution interacts with the glucose molecules to produce a compound that reacts with the alloy. This reaction triggers an electrical signal, indicating the concentration of glucose in the sweat. With a smaller alkaline solution chamber, the entire device is roughly the size of a quarter and is flexible enough to maintain a secure attachment to the human body, Cheng said. In a proof-of-concept test, the researchers used a skin-safe adhesive to attach the reusable device to a person’s arm one hour and three hours after a meal. The subject performed a brief workout — just enough to produce sweat — right before each measurement time. A few minutes after collecting the sweat, the researchers found that the detected glucose concentration dropped from the first measurement to the next. The glucose measurements from the device were verified by measurements made with a commercially available glucose monitor. Cheng and the team plan to improve upon their prototype for future applications, including addressing how patients or clinicians may use the sensor for incremental glucose measurements or continuous monitoring to determine treatment actions, such as administering insulin. They also intend to refine and expand this platform for more comfortable monitoring of other biomarkers that can be found in the sweat or interstitial fluids that fill the space between cells in the body. “We want to work with physicians and other health care providers to see how we can apply this technology for daily monitoring of a patient,” Cheng said. “This glucose sensor serves as a foundational example to show that we can improve the detection of biomarkers in sweat at extremely low concentrations.” For more information: https://www.psu.edu/news/research/story/monitoring-glucose-levels-no-needles-required/