Wearable pieces of health tech like the Apple Watch specialize in monitoring heart rates from the wrist. But the Apple Watch, and thousands of apps that seek to tell users about health, have come under serious criticism in recent years. Perhaps these devices and apps are missing a key ingredient: human skin is the largest organ in the body, so why shouldn't it also be our biggest data provider?
The closest we come today to utilizing this data source is strapping wearables to our wrists during a workout, but in the not-so-distant future a new type of wearable will emerge -- a patch of electronic skin (e-skin.)
A team of material scientists from China and the U.S. has designed a new type of e-skin that retains all the flexibility and lightness of other e-skin designs while also accounting for crucial human comfort factors, like breathability and bacterial resistance. This self-powered patch is also incredibly sensitive and can detect even the smallest physical cues in a face or joint, such as a frown or eye-twitch.
In addition to using this e-skin to improve the life-like qualities of futuristic robotics, this easy-to-wear e-skin can also improve communication between paralyzed patients and their loved ones.
"The comfort, safety, and health of e-skins are always neglected."
In a new study published Friday in the journal Science Advances, the team of researchers describes how their approach to designing e-skin differs from previous models in a few important ways.
"[E]-skins are able to detect and quantify a diversity of environmental stimuli, including temperature, humidity, pressure, vibration, and haptics, through transforming them into real-time and visualized electronic impulses," write authors. "[But] the comfort, safety, and health of e-skins are always neglected, which hinders their practical applications to a great extent."
While previous studies have worked to improve the self-healing, shape memory, and electroluminescence of e-skin models, the authors argue that these have done little to improve the actual experience of wearing an e-skin. To solve this problem, the team created an e-skin that maintained the sensitivity of other models while also factoring in the need for antibacterial and biodegradable materials and breathability when worn.
In fact, the authors write that when comparing the breathability of this e-skin to other common materials, they found it was more breathable than a pair of jeans.
To achieve this, the researchers designed an e-skin by sandwiching together silver nanowire between forms of acid and alcohol to create nanofiber generators. By adjusting the ratio between the nanowire, acid, and alcohol, the team was able to tune the antibacterial resistance of the e-skin. When testing just how antibacterial the e-skin was, the researchers found that after a 24-hour incubation period with common bacteria E. coli and S. aureus, the e-skin killed 54 and 88 percent of the respective bacteria colonies.
Beyond its bacterial resistance, the team also tested how biodegradable the e-skin was and found that it nearly completely degraded (more than 90 percent) in only 30-days. Compared to other e-skins -- let alone wearables -- that end up in landfills after their usefulness expires, 30-days is a step-up.
When tested on humans, these e-skins were able to pick-up micromovements that researchers say could have important clinical applications, especially for patients who may be mostly paralyzed and struggle to communicate emotions and thoughts to doctors or family members.
"Frowning, blinking, smiling, and other facial expressions are the most intuitive platforms to convey human emotions and are also the main external communication channels for general paralyzed patients," write the authors. "By sticking an e-skin on the forehead, regular and repeatable voltage signals are monitored during normal and frown alternating movements. Tiny muscle movements caused by microexpression can be easily captured by the voltage signal variations."
The sensitivity of the e-skin also allowed the researchers to easily distinguish from different types of micromovements, such as slow blinking versus rapid blinking, that may be markers of different emotional states.
While there is still more work to be done to ensure these e-skins can stand the test of time (e.g. future-proofing them against excess sweat or pollutants) the authors hope that their device can improve how we interact with our physical world.
"On the basis of the merits of highly sensitive self-powered electrical responses, diversified practical functions, and remarkable human/environmental friendliness, the e-skin can assist the human body to navigate our physical world with ease."
Abstract: Mimicking the comprehensive functions of human sensing via electronic skins (e-skins) is highly interesting for the development of human-machine interactions and artificial intelligences. Some e-skins with high sensitivity and stability were developed; however, little attention is paid to their comfortability, environmental friendliness, and antibacterial activity. Here, we report a breathable, biodegradable, and antibacterial e-skin based on all-nanofiber triboelectric nanogenerators, which is fabricated by sandwiching silver nanowire (Ag NW) between polylactic-co-glycolic acid (PLGA) and polyvinyl alcohol (PVA). With micro-to-nano hierarchical porous structure, the e-skin has high specific surface area for contact electrification and numerous capillary channels for thermal-moisture transfer. Through adjusting the concentration of Ag NW and the selection of PVA and PLGA, the antibacterial and biodegradable capability of e-skins can be tuned, respectively. Our e-skin can achieve real-time and self-powered monitoring of whole-body physiological signal and joint movement. This work provides a previously unexplored strategy for multifunctional e-skins with excellent practicability.