Babies in the neonatal intensive care unit (NICU) are tiny, fragile and covered in wires. Wires for monitoring heart rate, wires for monitoring blood pressure, wires for monitoring temperature, wires for monitoring blood oxygenation. It makes it hard for the babies to wave their little arms, and it makes it even harder for parents to touch them, let alone pick them up.
Now, thanks to an advance in materials science, those wires may eventually disappear. Researchers at Northwestern University have developed incredibly thin, stretchable electronic patches for monitoring a wide variety of vital signs and bodily movements.
These patches “have the strong potential to make human healthcare and rehabilitation much more efficient and effective,” says John Rogers, the scientists who led the research.
The patches, which are now in human trials, look more or less like temporary tattoos. They’re created by putting tiny semiconductor chips on a stretchable substrate. The substrate is embedded with wavy patterns of metal filaments, which make it possible to carry electrical signals. The whole thing uses tiny antennae to transmit information wirelessly, so they don’t need to be attached to any wires or tubing. Rogers calls the patches “epidermal electronics.”
The benefit to babies in the NICU is obvious—in early trials, one baby who kept pulling off the wires of traditional sensors was totally unbothered by the epidermal electronics. But it’s not just NICU babies who stand to gain. Rogers and his team are also trialing epidermal electronics in several different areas. One area is rehabilitative medicine. Beginning in June, Rogers’ team will be launching a trial on patients with Parkinson’s disease, who are often debilitated by involuntary tremors. The trial will involve placing patches on various places all over the subject’s body and using them to measure muscle activity and characteristics of motion.
“The goal is to develop sufficiently precise analytics that could allow us to determine the really early onset of tremors, characterize the development of the disease, and also to determine the efficacy of the drugs,” Rogers says.
By monitoring patients’ neuromuscular activity, researchers could even figure out, based on minute increases in tremors, whether patients had been skipping their medications.
The same technology could be useful for stroke patients, making it possible for doctors to track their progress while they undergo rehabilitation at home.
Rogers and his team are also trialing epidermal electronics with various professional sports teams (Rogers isn’t at liberty to say which ones, but they include football, baseball and basketball teams). The technology could track training progress, allowing coaches to see, for example, if a pitcher is using correct form. It could also monitor the tiny changes in movement that signal fatigue on the field, letting coaches see when a player is getting too tired to play optimally, long before it’s obvious to anyone else.
“The idea is to design these devices in such a way that you can monitor heart rate, pitching mechanics, free throw shooting mechanics [and more],” Rogers says.
Rogers has been working on flexible electronics technology for years. In 2011, he published an article in Science detailing a prototype of his skin patches, which he later improved to make them more durable. In 2015, his lab came out with a version of the patches that could measure blood flow, while last year they created a patch to analyze sweat for biochemical markers. In a commentary on Rogers' work in Science, engineer Zhenqiang Ma wrote that epidermal electronics could potentially solve many of the current problems with health monitoring and "allow monitoring to be simpler, more reliable,and uninterrupted." He also wrote that "other types of electronic skins with applications beyond physiology, such as body heat harvesting and wearable radios, may also point to interesting directions for future work."
While Rogers is considered the father of epidermal electronics, a number of researchers are working on advancing the technology in a number of ways. Some believe flexible electronics will one day be used for applications beyond the skin, such as heart pacemakers, and may even become ubiquitous as continuous health monitors, constantly checking things like blood oxygen levels and blood sugar. Researchers from Stanford to MIT to universities in Japan and Sweden are working on various aspects of flexible electronics, including making the technology smaller and more durable.
The cosmetics company Laroche-Posay has created a heart-shaped patch for monitoring UV exposure; there's currently a waitlist for the device. Unlike Rogers' epidermal electronics, which transmit data wirelessly, the UV patch works by changing color; a corresponding smartphone app reads the color changes and tells you if you've been in the sun too long.
After 10 years of work creating epidermal electronics, the remaining challenges are less about engineering than about optimization and security, Rogers says. Since the devices transmit wirelessly, data encryption will be a concern. Rogers also hopes to develop the devices further, potentially giving them the ability to sample biofluids like sweat and do chemical analysis of biomarkers that indicate health or disease. (Rogers has already done work in this area) The team is also looking at developing devices to deliver fluids through the skin, which could be an unobtrusive way to give medications.
“We’re pretty optimistic about it,” Rogers says. “There are a lot of things we can do today, and there’s a lot of potential for additional things in the future.”