Smartphone app to reliably diagnose irregular heartbeat or atrial fibrillation

Researchers from the University of Turku developed a smartphone app to detect atrial fibrillation with phone alone, without any extra equipment. This application provides a potential tool for timely diagnosis of atrial fibrillation as it is crucial for effective stroke prevention. The results of the study were published in the journal Circulation.

Smartphone app to detect atrial fibrillation or irregular heartbeat.
Credit: Hannah Oksanen, University of Turku.

Researchers conducted a study on three hundred patients with heart problems, 50% had atrial fibrillation. The researchers managed to identify the patients with atrial fibrillation from the other group with a smartphone with around 96% accuracy. According to Chief Physician and Professor of Cardiology Juhani Airaksinen from Turku University Hospital, this is the first time that ordinary consumer electronics have achieved such reliable results.

The technology behind the application involves using small accelerometers that are present in most smartphones. Researchers call this technique mechanochardiography, as it uses mechanical stimulus to generate heart trace.

The researchers want to make this app available for all as quickly as possible. According to Mr. Koivisto, the commercialization of the method is advancing quickly.

Reference: Jaakkola, Jussi, Samuli Jaakkola, Olli Lahdenoja, Tero Hurnanen, Tero Koivisto, Mikko Pänkäälä, Timo Knuutila, Tuomas O. Kiviniemi, Tuija Vasankari, and K.e. Juhani Airaksinen. “Mobile Phone Detection of Atrial Fibrillation With Mechanocardiography: The MODE-AF Study (Mobile Phone Detection of Atrial Fibrillation).” Circulation, 2018. doi:10.1161/circulationaha.117.032804.

Adapted from press release by the University of  Turku.

New nanosensor technology to detect osteoarthritis biomarker

Researchers at Wake Forest Baptist Medical Center have been able to analyze hyaluronic acid using solid-state nanopore sensor. This technique allows them to study its role in osteoarthritis and other inflammatory joint disorders. This technique is first of a kind and is a significant improvement regarding relative ease to perform and high precision from other techniques like gel electrophoresis, mass spectroscopy or size exclusion chromatography.

The study was led by Hall and Elaheh Rahbar, Ph.D., of Wake Forest Baptist, and conducted in collaboration with scientists at Cornell University and the University of Oklahoma. The study is published in the journal of Nature Communications.

“Our results established a new, quantitative method for the assessment of a significant molecular biomarker that bridges a gap in the conventional technology,” said Adam R. Hall. “The sensitivity, speed and small sample requirements of this approach make it attractive as the basis for a powerful analytic tool with distinct advantages over current assessment technologies.”

In the study researchers first employed synthetic hyaluronic acid polymers to validate the measurement approach. They then used the platform to determine the size distribution of hyaluronic acid extracted from the synovial fluid of a horse model of osteoarthritis.

The measurement approach consists of a microchip with a single hole or pore in it that is a few nanometers wide that is small enough that only individual molecules can pass. And as they do, each can be detected and analyzed. By applying the approach to hyaluronic acid molecules, the researchers were able to determine their size one-by-one. Hyaluronic acid size distribution changes over time in osteoarthritis so this technology could help better assess disease progression, Hall said.

Researchers hope to conduct their next study in humans, and then extend the technology with other diseases where hyaluronic acid and similar molecules play a role, including traumatic injuries and cancer.

Citation: Rivas, Felipe, Osama K. Zahid, Heidi L. Reesink, Bridgette T. Peal, Alan J. Nixon, Paul L. Deangelis, Aleksander Skardal, Elaheh Rahbar, and Adam R. Hall. “Label-free analysis of physiological hyaluronan size distribution with a solid-state nanopore sensor.” Nature Communications 9, no. 1 (2018). doi:10.1038/s41467-018-03439-x.

Adapted from press release by Wake Forest Baptist Medical Center.

Researchers create better wearable medical sensors based on graphene nano-flakes

Team of researchers at University of British Columbia Okanagan campus have developed a practical way to monitor and interpret human motion.The sensor is made by infusing graphene nano-flakes (GNF) into a rubber-like adhesive pad. Najjaran says they then tested the durability of the tiny sensor by stretching it to see if it can maintain accuracy under strains of up to 350 per cent of its original state. The device went through more than 10,000 cycles of stretching and relaxing while maintaining its electrical stability.

“We tested this sensor vigorously,” says Najjaran. “Not only did it maintain its form but more importantly it retained its sensory functionality. We have further demonstrated the efficacy of GNF-Pad as a haptic technology in real-time applications by precisely replicating the human finger gestures using a three-joint robotic finger.”

The goal was to make something that could stretch, be flexible and a reasonable size, and have the required sensitivity, performance, production cost, and robustness. Unlike an inertial measurement unit (an electronic unit that measures force and movement and is used in most step-based wearable technologies) Najjaran says the sensors need to be sensitive enough to respond to different and complex body motions. That includes infinitesimal movements like a heartbeat or a twitch of a finger, to large muscle movements from walking and running.

School of Engineering Professor and study co-author Mina Hoorfar says their results may help manufacturers create the next level of health monitoring and biomedical devices. “We have introduced an easy and highly repeatable fabrication method to create a highly sensitive sensor with outstanding mechanical and electrical properties at a very low cost,” says Hoorfar.

To demonstrate its practicality, researchers built three wearable devices including a knee band, a wristband and a glove. The wristband monitored heartbeats by sensing the pulse of the artery. In an entirely different range of motion, the finger and knee bands monitored finger gestures and larger scale muscle movements during walking, running, sitting down and standing up. The results, says Hoorfar, indicate an inexpensive device that has a high-level of sensitivity, selectivity and durability.

Citation: Larimi, Seyed Reza, Hojatollah Rezaei Nejad, Michael Oyatsi, Allen O’Brien, Mina Hoorfar, and Homayoun Najjaran. “Low-cost ultra-stretchable strain sensors for monitoring human motion and bio-signals.” Sensors and Actuators A: Physical 271 (2018): 182-91. doi:10.1016/j.sna.2018.01.028.

Research funding: Natural Sciences and Engineering Research Council.

Adapted from press release by the University of British Columbia.

Researchers develop ultra thin wearable skin electronics

This latest research by a Japanese academic-industrial collaboration, led by Professor Takao Someya at the University of Tokyo’s Graduate School of Engineering presents a new ultrathin, elastic display that fits snugly on the skin and can show the moving waveform of an electrocardiogram recorded by a breathable, on-skin electrode sensor. Combined with a wireless communication module, this integrated biomedical sensor system called “skin electronics” can transmit biometric data to the cloud.

Wearable skin electronic biosensors. Credit: 2018 Takao Someya Research Group.

The new integrated system combines a flexible, deformable display with a lightweight sensor composed of a breathable nanomesh electrode and wireless communication module. Medical data measured by the sensor, such as an electrocardiogram, can either be sent wirelessly to a smartphone for viewing or to the cloud for storage. In the latest research, the display showed a moving electrocardiogram waveform that was stored in memory.

The skin display, developed by a collaboration between researchers at the University of Tokyo’s Graduate School of Engineering and Dai Nippon Printing (DNP), a leading Japanese printing company, consists of a 16 x 24 array of micro LEDs and stretchable wiring mounted on a rubber sheet.

“Our skin display exhibits simple graphics with motion,” says Someya. “Because it is made from thin and soft materials, it can be deformed freely.” The display is stretchable by as much as 45 percent of its original length. It is far more resistant to the wear and tear of stretching than previous wearable displays. It is built on a novel structure that minimizes the stress resulting from stretching on the juncture of hard materials, such as the micro LEDs, and soft materials, like the elastic wiring a leading cause of damage for other models.

The nanomesh skin sensor can be worn on the skin continuously for a week without causing any inflammation. Although this sensor, developed in an earlier study, was capable of measuring temperature, pressure and myoelectricity (the electrical properties of muscle), it successfully recorded an electrocardiogram for the first time in the latest research.

The researchers applied tried-and-true methods used in the mass production of electronics – specifically, screen printing the silver wiring and mounting the micro LEDs on the rubber sheet with a chip mounter and solder paste commonly used in manufacturing printed circuit boards. DNP is looking to bring the integrated skin display to market within the next three years by improving the reliability of the stretchable devices through optimizing its structure, enhancing the production process for high integration, and overcoming technical challenges such as large-area coverage.

“The current aging society requires user-friendly wearable sensors for monitoring patient vitals in order to reduce the burden on patients and family members providing nursing care,” says Someya. “Our system could serve as one of the long-awaited solutions to fulfill this need, which will ultimately lead to improving the quality of life for many.”

Adapted from press release by the University of Tokyo.

Digital pill biosensors for monitoring opioid medication use

In a research paper published in the Anesthesia & Analgesia, Brigham and women’s hospital investigators report on the results from a pilot study of 15 individuals who received a prescription to take oxycodone digital pills as needed following treatment for acute fractures.

Recently first digital pill was approved by the FDA for use with the antipsychotic drug Abilify, used to treat schizophrenia, bipolar disorder and depression. Opioids such as oxycodone are frequently prescribed on an as-needed basis for managing acute conditions, but uncertainty exists around how patients take the prescribed drug. Digital pills may offer a unique window into patterns of medication usage.

To conduct their pilot study, the investigators approached 26 individuals in the Emergency Department who had been diagnosed with an acute fracture. (Fifteen completed the study.) The team instructed participants to use oxycodone (one to two 5-mg oxycodone digital pills every six to eight hours) as needed for pain. Unused pills were returned after seven days.

The team used the eTectRx ID-Cap system. Each pill in the system consists of a unique radiofrequency emitter and a standard gelatin capsule containing an oxycodone tablet. When the capsule dissolves, the medication is released, and chloride ions energize the emitter. The patient wears a sticky patch on their abdomen, attached to a cable reader (the size of an iPod) that stores data about pill ingestion. (Since the study was conducted, advances in the technology have miniaturized the reader and added steps to validate the user of the system and provide directed feedback through a smartphone app.)

The digital pill system recorded a total of 112 ingestion events, compared to 134 ingestions based on pill count (84 percent accuracy). However, all missed ingestion events were traced back to two study participants who ingested digital pills without wearing the reader or did not interact with the reader due to severe pain. Most oxycodone doses were ingested within the first three days after discharge. On average, patients ingested only six pills, despite being given 21.

Citation: Chai, Peter R., Stephanie Carreiro, Brendan J. Innes, Brittany Chapman, Kristin L. Schreiber, Robert R. Edwards, Adam W. Carrico, and Edward W. Boyer. “Oxycodone Ingestion Patterns in Acute Fracture Pain With Digital Pills.” Anesthesia & Analgesia 125, no. 6 (2017): 2105-112.
doi:10.1213/ane.0000000000002574
Funding: National Institutes of Health
Adapted from press release by Brigham And Women’s Hospital.

Artificial retina using synthetic and biological materials

A synthetic, soft tissue retina made of hydrogels and biological cell membrane proteins was developed by an Oxford University student Vanessa Restrepo-Schild. Research involved combining biological and synthetic tissues in a laboratory. Designed like a camera, the aqueous droplets containing bacteriorhodopsin (bR), a light-driven proton pump act as pixels, detecting and reacting to light to generate electrical signals, which can stimulate the neurons with resulting output recognized in grey scale.

The retina replica consists of soft water droplets (hydrogels) and biological cell membrane proteins.
Credit: Oxford University

The study, published in the journal Scientific Reports, shows that unlike existing artificial retinal implants, the cell-cultures are created from natural, biodegradable materials and do not contain foreign bodies or living entities. In this way the implant is less invasive than a mechanical devise, and is less likely to have an adverse reaction on the body.

This research could revolutionize the bionic implant industry with development of new, less invasive technologies that more closely resemble human body tissues, helping to treat degenerative eye conditions such as retinitis pigmentosa.

Currently synthetic retina has only been tested in laboratory conditions and further research is needed to see viability of this technology.

Miss Restrepo-Schild has filed a patent for the technology and the next phase of the work will see the Oxford team expand the replica’s function to include recognising different colours. Working with a much larger replica, the team will test the material’s ability to recognise different colours and potentially even shapes and symbols. Looking further ahead the research will expand to include animal testing and then a series of clinical trials in humans.

Citation: Schild, Vanessa Restrepo, Michael J. Booth, Stuart J. Box, Sam N. Olof, Kozhinjampara R. Mahendran, and Hagan Bayley. “Light-Patterned Current Generation in a Droplet Bilayer Array.” Scientific Reports 7 (2017): 46585. doi:10.1038/srep46585.
Adapted from press release by the Oxford University.

Glassy carbon electrodes advances brain-computer interface technology

The Center for Sensorimotor Neural Engineering-a collaboration of San Diego State University with the University of Washington and the Massachusetts Institute of Technology is working on an implantable brain chip that can record neural electrical signals and transmit them to receivers in the limb. Results of the research study utilizing above technology are published in the journal Nature Scientific Reports.

Glassy Carbon Electrodes for Brain-computer Interface technology
This image shows a sheet of glassy carbon electrodes patterned inside chips.
Credit: Sam Kassegne, San Diego State University.

When people suffer spinal cord injuries and lose mobility in their limbs, the brain can still send clear electrical impulses and the limbs can still receive them, but the signal gets lost in the damaged spinal cord. The brain chip the researchers works by bypassing the damage and restoring movement.

The technology, known as a brain-computer interface, records and transmits signals through electrodes, which are tiny pieces of material that read signals from brain chemicals known as neurotransmitters. The device works by recording and analyzing brain signals and convert them into a relevant electrical signal pattern, these signals are then transmitted to the limb’s nerves, or even to a prosthetic limb, restoring mobility and motor function.

The current state-of-the-art material for electrodes in these devices is thin-film platinum. The problem is that these electrodes can fracture and fall apart over time, said one of the study’s lead investigators, Sam Kassegne, deputy director for the CSNE at SDSU and a professor in the mechanical engineering department. To overcome this problem researchers developed electrodes made out of glassy carbon, a form of carbon. This material is about 10 times smoother than granular thin-film platinum, meaning it corrodes less easily under electrical stimulation and lasts much longer than platinum or other metal electrodes. Researchers are using these new and improved brain-computer interfaces to record neural signals both along the brain’s cortical surface and from inside the brain at the same time.

A doctoral graduate student in Kassegne’s lab, Mieko Hirabayashi, is exploring a slightly different application of this technology. She’s working with rats to find out whether precisely calibrated electrical stimulation using these electrodes can cause new neural growth within the spinal cord with hope to replicate these results in humans. The new glassy carbon electrodes will allow her to stimulate, read the electrical signals of and detect the presence of neurotransmitters in the spinal cord better than ever before.

Citation: Vomero, Maria, Elisa Castagnola, Francesca Ciarpella, Emma Maggiolini, Noah Goshi, Elena Zucchini, Stefano Carli, Luciano Fadiga, Sam Kassegne, and Davide Ricci. “Highly Stable Glassy Carbon Interfaces for Long-Term Neural Stimulation and Low-Noise Recording of Brain Activity.” Scientific Reports 7 (2017): 40332.
DOI:10.1038/srep40332.
Research funding: National Science Foundation.
Adapted from press release by San Diego State University.

Novel bio-signal measuring electrodes to advance health diagnosis using internet of things devices

Daegu Gyeongbuk Institute of Science and Technology (DGIST) announced that Professor Kyung-in Jang’s research team from the Department of Robotics Engineering succeeded in developing bio-signal measuring electrodes that can be mounted on Internet of Things (IoT) devices through joint research with a research team led by professor John Rogers of the University of Illinois, USA.

Optical image of bio-signal measurement electrode
design developed by Professor Jang’s research team.
The electrode generates such a large force that it holds
the circular magnet located under the glass only by
attraction (gravitation) of the magnetic field.
Credit: DGIST
The bio-signal measuring electrodes developed by the research team can be easily mounted onInternet of Things (IoT) devices for health diagnosis, thus they can measure bio-signals such as brain waves and electrocardiograms without additional analysis and measurement equipment while not interfering or restricting human activities.
Conventional hydro-gel based electrodes required external analysis and measurement devices to measure bio-signals due to their pulpy gel forms, which made their attachment to and detachment from IoT devices instable. In addition, since these electrodes were wet-bonded to the skin, there have been disadvantages that the characteristics of the electrodes deteriorated or their performance decreased when the electrodes were dried in the air over a long period.
In contrast, the electrodes developed by Professor Kyung-in Jang can be easily interlocked as if they are a part of Internet of Things (IoT) devices for health diagnosis. Also, since they are composed only of polymer and metal materials, they have the advantage of there being no possibility of drying in the air.

The bio-signal measurement electrodes developed by the research team consist of a composite material in which a magnetic material is folded with a soft and adhesive polymer, with a conductive electrode material wrapped around the composite material. The conductive electrode material electrically connects the bottom surface touching the skin and the top surface touching the electrode of the Internet of Things (IoT) device.

Electrodes with this structure reacting to the magnetic field can be easily attached and detached by using the attraction that occurs between the magnet and the electrode mounted on the IoT devices. Then, through the conductive electrode materials that connect the skin and the electrode part of the IoT device, the electric signals generated on the skin can be directly transmitted to the IoT device for health diagnosis.

The research team succeeded in storing and analyzing brain waves (electroencephalogram, EEG), electrocardiograms (ECG), eye movements (electrooculogram, EOG), and limb movements and muscle contractions (electromyogram, EMG) of the wearer for a long period through an experiment in which IoT devices with the electrodes are attached to various parts of the human body.

The bio-signal measurement electrodes can measure the bioelectric signal generated from the skin without loss or noise by using the Internet of Things (IoT) platform, thus they are expected to be applicable to the medical and healthcare fields since they cannot only measure the electrical signals of the body, but also analyze various forms of bio-signals such as body temperature change, skin change, and in-body ion concentration change.

Professor Kyung-in Jang said, “We have secured the source technology that can diagnose the state of human health anytime and anywhere by combining bio-electrode technology with Internet of Things (IoT) platforms utilizing advanced high-tech composite materials. We will carry out subsequent research to make it applicable for diseases that require ongoing medical diagnosis such as diabetes, insomnia, and epilepsy, and to make it available to people in medically vulnerable areas such as remote mountainous and rural areas.”

Citation: “Ferromagnetic, Folded Electrode Composite as a Soft Interface to the Skin for Long-Term Electrophysiological Recording”. Kyung-In Jang, Han Na Jung, Jung Woo Lee, Sheng Xu, Yu Hao Liu, Yinji Ma, Jae-Woong Jeong, Young Min Song, Jeonghyun Kim, Bong Hoon Kim, Anthony Banks, Jean Won Kwak, Yiyuan Yang, Dawei Shi, Zijun Wei, Xue Feng, Ungyu Paik, Yonggang Huang, Roozbeh Ghaffari, John A. Rogers.Advanced Functional Materials 2016 vol: 26 (40) pp: 7281-7290.
DOI: 10.1002/adfm.201603146
Adapted from press release by Daegu Gyeongbuk Institute of Science and Technology (DGIST).

New technology using gold wires on flexible plastic for wearable electronic devices

Researchers from National Institute of Standards and Technology (NIST) has come up with a way to build safe, nontoxic gold wires onto flexible, thin plastic film. Their demonstration potentially clears the path for a host of wearable electronic devices that monitor our health.

NIST research has found that the flexible plastic membrane on
 which wearables would be built might work better if the
membrane had microscopic holes in it.
Credit: Reyes-Hernandez/NIST
Wearable health monitors are already commonplace; bracelet-style fitness trackers have escaped mere utility to become a full-on fashion trend. But the medical field has its eye on something more profound, known as personalized medicine. The long-term goal is to keep track of hundreds of real-time changes in our bodies, from fluctuations in the amount of potassium in sweat to the level of particular sugars or proteins in the bloodstream. These changes manifest themselves a bit differently in each person, and some of them could mark the onset of disease in ways not yet apparent to a doctor’s eye. Wearable electronics might help spot those problems early.

First, though, engineers need a way to build them so that they work dependably and safely–a tall order for the metals that make up their circuits and the flexible surfaces or “substrates” on which they are built. Gold is a good option because it does not corrode, unlike most metals, and it has the added value of being nontoxic. But it’s also brittle. If you bend it, it tends to crack, potentially breaking completely– meaning thin gold wires might stop conducting electricity after a few twists of the body.

“Gold has been used to make wires that run across plastic surfaces, but until now the plastic has needed to be fairly rigid,” said Reyes-Hernandez. “You wouldn’t want it attached to you; it would be uncomfortable.”

Reyes-Hernandez doesn’t work on wearable electronics. His field is microfluidics, the study of tiny quantities of liquid and their flow, typically through narrow, thin channels. One day he was exploring a commercially available porous polyester membrane–it feels like ordinary plastic wrap, only a lot lighter and thinner–to see if its tiny holes could make it useful for separating different fluid components. He patterned some gold electrodes onto the membrane to create a simple device that would help with separations. While sitting at his desk, he twisted the plastic a few times and noticed the electrodes, which covered numerous pores as they crisscrossed the surface, still conducted electricity. This wasn’t the case with nonporous membranes. “Apparently the pores keep the gold from cracking as dramatically as usual,” he said. “The cracks are so tiny that the gold still conducts well after bending.”

Reyes-Hernandez said the porous membrane’s electrodes show even higher conductivity than their counterparts on rigid surfaces, an unexpected benefit that he cannot explain as yet. The next steps, he said, will be to test changes in conductivity over the long term after many bends and twists, and also to build some sort of sensor out of the electrode-coated membrane to explore its real-world usability. “This thin membrane could fit into very small places,” he said, “and its flexibility and high conductivity make it a very special material, almost one of a kind.”

Citation: “Flexible Thin-Film Electrodes on Porous Polyester Membranes for Wearable Sensors”.
Aveek Gangopadhyay, Brian J. Nablo, Mulpuri V. Rao,  Darwin R. Reyes. Advanced Engineering Materials 2016.
DOI: 10.1002/adem.201600592
Adapted from press release by National Institute of Standards and Technology.

Wearable biosensor to test sweat

Researchers has developed soft, flexible microfluidic device that easily adheres to the skin and measures the wearer’s sweat to show how his or her body is responding to exercise. A little larger than a quarter and about the same thickness, the simple, low-cost device analyzes pH and concentrations of glucose, chloride and lactate.

Credit: John A Rogers, Northwestern University

“Sweat is a rich, chemical broth containing a number of important chemical compounds with physiological health information. By expanding our previously developed ‘epidermal’ electronics platform to include a complex network of microfluidic channels and storage reservoirs, we now can perform biochemical analysis of this important biofluid,” said John A. Rogers, who led the multi-institution research team that created the ‘lab on the skin.

Rogers is the Louis Simpson and Kimberly Querrey Professor of Materials Science and Engineering, Biomedical Engineering and Neurological Surgery in the McCormick School of Engineering and Northwestern University Feinberg School of Medicine.  Rogers and his longtime collaborator Yonggang Huang are pioneers in developing skin-like stretchable electronics that move naturally with the skin, and this is their first device to monitor physiological health by analyzing biofluids.

In a study of accuracy and durability, the device was tested on two different groups of athletes: one cycling indoors in a fitness center under controlled conditions and the other participating in the El Tour de Tucson, a long-distance bicycle race in arid and complex conditions. The researchers placed the device on the arms and backs of the athletes to capture sweat. Details of the versatile platform for sweat analysis were published in the journal Science Translational Medicine.

During moderate or vigorous exercise, sweat winds through the tiny microscopic channels of the device and into four different small, circular compartments. In the compartments, reactions with chemical reagents result in visible color changes in ways that quantitatively relate to pH and concentrations of glucose, chloride and lactate.  When a smartphone is brought into proximity with the device, the wireless electronics trigger an app that captures a photo of the device and analyzes the image to yield data on the biomarker concentrations.

In the group that cycled indoors, the researchers compared the new device’s biomarker readouts to conventional laboratory analysis of the same sweat and found the two sets of results agreed with each other. (Conventional methods include capturing sweat with absorbent patches taped to the skin and analyzing them off-site.)

With the long-distance cyclists, the researchers tested the durability of the device in the complex and unpredictable conditions of the desert. They found the devices to be robust: They stayed adhered to the athletes’ skin, did not leak and provided the kind of quality information the researchers sought.

Citation: “A soft, wearable microfluidic device for the capture, storage, and colorimetric sensing of sweat”. Ahyeon Kohl, Daeshik Kang, Yeguang Xue, Seungmin Lee, Rafal M. Pielak, Jeonghyun Kim1, Taehwan Hwang, Seunghwan Min, Anthony Banks, Philippe Bastien, Megan C. Manco, Liang Wang, Kaitlyn R. Ammann, Kyung-In Jang, Phillip Won, Seungyong Han, Roozbeh Ghaffari, Ungyu Paik, Marvin J. Slepian, Guive Balooch, Yonggang Huang and John A. Rogers. Science Translational Medicine  23 Nov 2016: Vol. 8, Issue 366, pp. 366ra165
DOI: 10.1126/scitranslmed.aaf2593
Research funding: L’Oréal, Frederick Seitz Materials Research Laboratory at the University of Illinois at Urbana-Champaign, National Research Foundation of Korea and National Institutes of Health.
Adapted from news release by Northwestern University.