Rewritable, recyclable ‘smart skin’ monitors biological signals on demand

The details of this smart skin, including its ability to be reprogrammed and recycled, were published in Advanced Materials. The paper is part of the “Rising Stars” series, highlighting the work of early career researchers globally. A provisional patent application has also been filed.

"Despite significant efforts on wearable sensors for health monitoring, there haven’t been multifunctional skin-interfaced electronics with intrinsic adhesion on a single material platform prepared by low-cost, efficient fabrication methods,"said Huanyu "Larry" Cheng, the James L. Henderson, Jr. Memorial Associate Professor of Engineering Science and Mechanics at Penn State. "This work introduces a skin-attachable, reprogrammable, multifunctional adhesive device patch fabricated by simple and low-cost laser scribing."

Cheng’s team previously developed biomarker sensors using laser-induced graphene (LIG), which involves using a laser to pattern 3D networks on a porous, flexible substrate. The interactions between the laser and the substrate materials produce conductive graphene.

LIG-based sensors on flexible substrates are not intrinsically stretchable and can’t conform to human skin for bio-sensing. Human skin changes shape, temperature, and moisture levels, especially during physical exertion when monitoring heart rate, nerve performance, or sweat glucose levels might be necessary. Although LIG can be transferred to stretchable elastomers, the process can reduce its quality.

The device can monitor the pH value, glucose, and lactate concentrations in sweat and can be reprogrammed to monitor heart rate, nerve performance, and sweat glucose concentrations in real-time. Reprogramming is as simple as applying clear tape over the LIG networks and peeling them off. The substrate can then be re-lasered to new specifications up to four times before it becomes too thin, after which the entire device can be recycled.

Cheng noted that the device remains adhesive and functional even when the skin is slick with sweat or water. Currently powered by batteries or near-field communication modules, like a wireless charger, the device could potentially harvest energy and communicate over radio frequencies.

Researchers aim to develop a standalone, stretchable adhesive platform capable of sensing desired biomarkers and monitoring electrophysical signals. The team plans to work with physicians to apply the platform for managing various diseases such as diabetes and monitoring acute issues like infections or wounds.

This research was funded by the U.S. National Institutes of Health, the U.S. National Science Foundation, Penn State, the University of Electronic Science and Technology of China, and the National Natural Science Foundation of China.

MEDICA-tradefair.com; Source: Penn State