A wearable sensor can monitor levels of metabolites and nutrients in a person’s blood by analyzing their sweat

via Caltech

There are numerous things to dislike about going to the doctor: Paying a copay, sitting in the waiting room, out-of-date magazines, sick people coughing without covering their mouths. For many, though, the worst thing about a doctor’s visit is getting stuck with a needle. Blood tests are a tried-and-true way of evaluating what is going on with your body, but the discomfort is unavoidable. Or maybe not, say Caltech scientists.

In a new paper published in Nature Biotechnology, researchers led by Wei Gao, assistant professor of medical engineering, describe a mass-producible wearable sensor that can monitor levels of metabolites and nutrients in a person’s blood by analyzing their sweat. Previously developed sweat sensors mostly target compounds that appear in high concentrations, such as electrolytes, glucose, and lactate. Gao’s sweat sensor is more sensitive than current devices and can detect sweat compounds of much lower concentrations, in addition to being easier to manufacture, the researchers say.

The development of such sensors would allow doctors to continuously monitor the condition of patients with illnesses like cardiovascular disease, diabetes, or kidney disease, all of which result in abnormal levels of nutrients or metabolites in the bloodstream. Patients would benefit from having their physician better informed of their condition, while also avoiding invasive and painful encounters with hypodermic needles.

“Such wearable sweat sensors have the potential to rapidly, continuously, and noninvasively capture changes in health at molecular levels,” Gao says. “They could enable personalized monitoring, early diagnosis, and timely intervention.”

Gao’s work is focused on developing devices based on microfluidics, a name for technologies that manipulate tiny amounts of liquids, usually through channels less than a quarter of a millimeter in width. Microfluidics are ideal for an application of this sort because they minimize the influence of sweat evaporation and skin contamination on the sensing accuracy. As freshly supplied sweat flows through the microchannels, the device can make more accurate measurements of sweat and can capture temporal changes in concentrations.

Until now, Gao and his colleagues say, microfluidic-based wearable sensors were mostly fabricated with a lithography-evaporation process, which requires complicated and expensive fabrication processes. His team instead opted to make their biosensors out of graphene, a sheet-like form of carbon. Both the graphene-based sensors and the tiny microfluidics channels are created by engraving the plastic sheets with a carbon dioxide laser, a device that is now so common that it is available to home hobbyists.

The research team opted to have their sensor measure respiratory rate, heart rate, and levels of uric acid and tyrosine. Tyrosine was chosen because it can be an indicator of metabolic disorders, liver disease, eating disorders, and neuropsychiatric conditions. Uric acid was chosen because, at elevated levels, it is associated with gout, a painful joint condition that is on the rise globally. Gout occurs when high levels of uric acid in the body begin crystallizing in the joints, particularly those of the feet, causing irritation and inflammation.

To see how well the sensors performed, the researchers ran a series of tests with healthy individuals and patients. To check sweat tyrosine levels, which are influenced by a person’s physical fitness, they used two groups of people: trained athletes and individuals of average fitness. As expected, the sensors showed lower levels of tyrosine in the sweat of the athletes. To check uric acid levels, they took a group of healthy individuals and monitored their sweat while they were fasting as well as after they ate a meal rich in purines, compounds in food that are metabolized into uric acid. The sensor showed uric acid levels rising after the meal. Gao’s team also performed a similar test with gout patients. Their uric acid levels, the sensor showed, were much higher than those of healthy people.

To check the accuracy of the sensors, the researchers also drew blood samples from the gout patients and healthy subjects. The sensors’ measurements of uric acid levels strongly correlated with levels of the compound in the blood.

Gao says the high sensitivity of the sensors, along with the ease with which they can be manufactured, means they could eventually be used by patients at home to monitor conditions like gout, diabetes, and cardiovascular diseases. Having accurate real-time information about their health could even allow a patient to adjust their own medication levels and diet as required.

“Considering that abnormal circulating nutrients and metabolites are related to a number of health conditions, the information collected from such wearable sensors will be invaluable for both research and medical treatment,” Gao says.

Learn more: Wearable Sweat Sensor Detects Gout-Causing Compounds



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Continuous-variable quantum key distribution over commercial fiber networks gets more real for metropolitan areas

The city of Guangzhou, one of the field test locations

Successful new field tests of a continuous-variable quantum key distribution (CV-QKD) system over commercial fiber networks could pave the way to its use in metropolitan areas.

That is the key achievement from a joint team of Chinese scientists, published today in Quantum Science and Technology, which demonstrates CV-QKD transmission over commercial deployed fiber link with a distance of 50 kilometres.

Team leader and lead author, Prof. Hong Guo, from a joint team of Peking University and Beijing University of Posts and Telecommunications (PKU-BUPT joint team), Beijing, said: “CV-QKD provides, in principle, unconditional secret keys to protect people’s data – such as banking information, emails and passwords.

“It has attracted much attention in the past few years, because it uses standard telecom components that operate at room temperature, instead of specific quantum devices such as single photon detectors etc, and it has potentially much higher secret key rates. However, most previous long-distance CV-QKD demonstrations were only done in laboratory fiber, without the disturbances caused by the field environment.”

Lead authors Dr. Yichen Zhang and Prof. Song Yu, from the PKU-BUPT joint team, Beijing, said: “There are several challenges to bringing a practical CV-QKD system from a laboratory setup to the real world. Deployed commercial dark fibers are inevitably subject to much stronger perturbations from changing environmental conditions and physical stress. This in turn causes severe disturbances of the transmitted quantum states.

“They also suffer from higher losses due to splices, sharp bends and inter-fiber couplings. The software and hardware of CV-QKD modules must not only be designed to cope with all the conditions affecting the transmission fiber, but must also be robustly engineered to operate in premises designed for standard telecom equipment. Furthermore, as the systems need to run continuously and without frequent attention, they need to be designed to automaticallyrecover from any errors and shield end users from service interruptions.”

The PKU-BUPT joint research team carried out two field tests of CV-QKD over commercial fiber networks in two cities of China – Xi’an and Guangzhou – achieving transmission distances of 30.02 km (12.48 dB loss) and 49.85 km (11.62 dB loss), respectively.

Prof. Hong Guo said: “The longest previous field tests of a CV-QKD system were over a 17.52 km deployed fiber (10.25 dB loss) and a 17.7 km deployed fiber (5.6 dB loss), where the secret key rates were 0.2 kbps and 0.3 kbps, respectively.

“Comparing with these results, our results show a more than twice transmission distance, and a two orders-of-magnitude higher secret key rates, though in more lossy commercial fiber links.

“This is a significant step in bringing CV-QKD closer to everyday use. It has pushed CV-QKD towards a more practical setting, and, naturally, one may expect that a quantum-guaranteedsecure metropolitan network could be built within reach of current technologies.”

Learn more: Secure metropolitan quantum networks move a step closer


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Major challenge solved in the production of low-cost solar cells

A model of a perovskite solar cell, showing its different layers. Professor André D. Taylor has been working to solve fabrication challenges with perovskite cells

Spray Coating Could Make Perovskite an Inexpensive Alternative to Silicon for Solar Panels

An international team of university researchers today reports solving a major fabrication challenge for perovskite cells — the intriguing potential challengers to silicon-based solar cells.

These crystalline structures show great promise because they can absorb almost all wavelengths of light. Perovskite solar cells are already commercialized on a small scale, but recent vast improvements in their power conversion efficiency (PCE) are driving interest in using them as low-cost alternatives for solar panels.

In the cover article published online today for the June 28, 2018 issue of Nanoscale, a publication of the Royal Society of Chemistry, the research team reveals a new scalable means of applying a critical component to perovskite cells to solve some major fabrication challenges. The researchers were able to apply the critical electron transport layer (ETL) in perovskite photovoltaic cells in a new way — spray coating — to imbue the ETL with superior conductivity and a strong interface with its neighbor, the perovskite layer.

The research is led by André D. Taylor, an associate professor in the NYU Tandon School of Engineering’s Chemical and Biomolecular Engineering Department, with Yifan Zheng, the first author on the paper and a Peking University researcher. Co-authors are from the University of Electronic Science and Technology of China, Yale University, and Johns Hopkins University.

Most solar cells are “sandwiches” of materials layered in such a way that when light hits the cell’s surface, it excites electrons in negatively charged material and sets up an electric current by moving the electrons toward a latticework of positively charged “holes.” In perovskite solar cells with a simple planar orientation called p-i-n (or n-i-p when inverted), the perovskite constitutes the light-trapping intrinsic layer (the “i” in p-i-n) between the negatively charged ETL and a positively charged hole transport layer (HTL).

When the positively and negatively charged layers are separated, the architecture behaves like a subatomic game of Pachinko in which photons from a light source dislodge unstable electrons from the ETL, causing them to fall toward the positive HTL side of the sandwich. The perovskite layer expedites this flow. While perovskite makes for an ideal intrinsic layer because of its strong affinity both for holes and electrons and its quick reaction time, commercial-scale fabrication has proved challenging partly because it is difficult to effectively apply a uniform ETL layer over the crystalline surface of the perovskite.

The researchers chose the compound [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) because of its track record as an ETL material and because PCBM applied in a rough layer offers the possibility of improved conductivity, less-penetrable interface contact, and enhanced light trapping.

“Very little research has been done on ETL options for the planar p-i-n design,” said Taylor. “The key challenge in planar cells is, how do you actually assemble them in a way that doesn’t destroy the adjacent layers?”

The most common method is spin casting, which involves spinning the cell and allowing centripetal force to disperse the ETL fluid over the perovskite substrate. But this technique is limited to small surfaces and results in an inconsistent layer that lowers the performance of the solar cell. Spin casting is also inimicable to commercial production of large solar panels by such methods as roll-to-roll manufacture, for which the flexible p-i-n planar perovskite architecture is otherwise well suited.

The researchers instead turned to spray coating, which applies the ETL uniformly across a large area and is suitable for manufacturing large solar panels. They reported a 30 percent efficiency gain over other ETLs – from a PCE of 13 percent to over 17 percent – and fewer defects.

Added Taylor, “Our approach is concise, highly reproducible, and scalable. It suggests that spray coating the PCBM ETL could have broad appeal toward improving the efficiency baseline of perovskite solar cells and providing an ideal platform for record-breaking p-i-n perovskite solar cells in the near future.”

Learn more: Researchers Solve Major Challenge in Mass Production of Low-Cost Solar Cells


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PowerPoint has a new job: Producing self-folding three-dimensional origami structures from photocurable liquid polymers

A tiny origami structure created through a self-folding process is shown on a quarter for size comparison. (Credit: Rob Felt, Georgia Tech)

Researchers at the Georgia Institute of Technology and Peking University have found a new use for the ubiquitous PowerPoint slide: The technique involves projecting a grayscale pattern of light and dark shapes onto a thin layer of liquid acrylate polymer placed in a plate or between two glass slides. A photoinitiator material mixed into the polymer initiates a crosslinking reaction when struck by light from an ordinary LED projector, causing a solid film to form. A light-absorbing dye in the polymer serves as a regulator for the light. Due to the complicated interaction between the evolution of the polymer network and volume shrinkage during photo curing, areas of the polymer that receive less light exhibit more apparent bending behavior.

When the newly-created polymer film is removed from the liquid polymer, the stress created in the film by the differential shrinkage causes the folding to begin. To make the most complex origami structures, the researchers shine light onto both sides of the structures.

Origami structures produced so far include tiny tables, capsules, flowers, birds and the traditional miura-ori fold – all about a half-inch in size. The origami structures could have applications in soft robots, microelectronics, soft actuators, mechanical metamaterials and biomedical devices.

“The basic idea of our method is to utilize the volume shrinkage phenomenon during photo-polymerization,” said Jerry Qi, a professor in the Woodruff School of Mechanical Engineering at Georgia Tech. “During a specific type of photopolymerization, frontal photopolymerization, the liquid resin is cured continuously from the side under light irradiation toward the inner side. This creates a non-uniform stress field that drives the film to bend along the direction of light path.”

Details of the work were published April 28 in the journal Science Advances. The research was supported by the National Science Foundation, the Air Force Office of Scientific Research and the Chinese Scholarship Council. It is believed to be the first application to create self-folding origami structures through the control of volume shrinkage during patterned photopolymerization.

The process that creates the shrinkage phenomenon is considered harmful in other uses of the polymer.

“Volume shrinkage of polymer was always assumed to be detrimental in the fabrication of composites and in the conventional 3-D printing technology,” said Daining Fang, a co-author of the paper and a professor at Peking University when the research was done. “Our work shows that with a change of perspective, this phenomenon can become quite useful.” Fang is now at Beijing Institute of Technology.

To make the most complex shapes with bending in both directions, the researchers can flip the patterned film over to create crosslinking on the other side.

“We have developed two types of fabrication processes,” said Zeang Zhao, a Ph.D. student at Georgia Tech and Peking University. “In the first one, you can just shine the light pattern towards a layer of liquid resin, and then you will get the origami structure. In the second one, you may need to flip the layer and shine a second pattern. This second process gives you much wider design freedom.”

Light is shined onto the film for five to ten seconds, which produces a film about 200 microns thick. “The areas that receive light become solid; the other parts of the pattern remain liquid, and the structure can then be removed from the liquid polymer,” said Qi. “The technique is very simple.”

Frontal photopolymerization is a process in which a polymer film is continuously cured from one side in a thick layer of liquid resin. In the presence of strong light attenuation, the solidification front initiates at the surface upon illumination and propagates toward the liquid side as the irradiation time increases. The process can be delicately tuned by controlling the illumination time and the light intensity, and the method has been used to fabricate microfluidic devices and synthesize microparticles.

The researchers used poly(ethylene glycol) diacrylate in this demonstration, but the technique should work with a broad range of photocurable polymers. An orange dye was used in the demonstration, but other dyes could produce structures in a range of different colors.

For the proof-of-principle, Zhao created a PowerPoint pattern by hand. To scale the process up, the system could be connected to a computer-aided design (CAD) tool for generating more precise grayscale patterns.

Qi believes the technique could be used to produce structures as much as an inch in size. “The self-folding requires relatively thin films which might not be possible in larger structures,” he said.

Added Qi, “We have developed a simple approach to fold a thin sheet of polymer into complicated three-dimensional origami structures. Our approach is not limited by specific materials, and the patterning is so simple that anybody with PowerPoint and a projector could do it.”

Learn more: PowerPoint & LED Projector Enable New Technique for Self-Folding Origami



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Promising new treatment for lupus on the horizon

via Monash University

via Monash University

A drug originally used to boost the immune system is showing promise as a potential new treatment for lupus, joint Monash University and Peking University research published today shows. Lupus is an autoimmune disease, where the immune system attacks the body’s own organs and tissues.

An international team of scientists from Australia and China have, for the first time, shown in a study published in Nature Medicine, that a natural immune system protein called IL-2 can help restore balance to the overactive immune system of lupus patients. The drug could soon be rolled out for clinical trials in lupus treatment.

Monash Biomedicine Discovery Institute researcher, Dr Di Yu and Professor Zhanguo Li from Peking University People’s Hospital in China co-led the study.

Dr Yu said he hoped the drug could be approved as a lupus treatment within a handful of years.

“This drug, which can help the immune system fight against cancer, was approved in the 1990s but is not commonly used now. We’re now using this drug for a different purpose, based on our new knowledge of the immune system,” Dr Yu said.

“The amount we tested for treating lupus is much less than the dose used in treating cancers. We observed the treatment was safe and showed promising results, so there’s reason to believe formal trials could begin almost immediately,” he said.

Dr Yu said lupus could be a serious disease, and that it hadn’t been able to be treated in a very satisfactory way in the past.

IL-2 is a protein that regulates the activity of white blood cells, which are an important part of the immune system that protect the body against infections. In cancer therapy, patients are given large doses of IL-2 to stimulate their immune system but, paradoxically, the low dose IL-2 given to lupus sufferers in this study actually supressed the overactive part of their immune system that attacks their body. The research also showed the “self-checking” part of the immune system that prevents an overactive immune response, called regulatory T cells, increased after IL-2 treatment.

Professor Eric Morand, fellow Monash University researcher on the study and founder of the Asia Pacific Lupus Collaboration, said that in this study, IL-2 was given to people whose lupus wasn’t responding well to standard treatments.

“The real promise of this treatment is that it calms the hyperactive immune system through multiple mechanisms, which is very important as this new therapy may be effective for many patients,” Professor Morand said.

”As the drug has been on the market for some time for other diseases, it can be rapidly put into formal trials for lupus treatment right away.”

Learn more: Promising new treatment for lupus on the horizon



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