Skin‐Friendly Electronics for Acquiring Human Physiological Signatures

Abstract

exercise that may last for hours or even days. [1,6,7] Much effort has been invested to increase adhesion by improving/optimizing the mechanical properties, thickness, and structural design of the device substrate. [8,9] However, just like many skin adhesives and transdermal patches, the strong adhesive design in many skin-mounted devices usually results in difficult detachment after their use, causing skin irritation, pain and even secondary damage to the wound when used, for example, as a wound healing dressing. [10] Strategies to design epidermal devices with strong adhesion and easy (preferably triggered, ondemand) detachment properties have yet to be developed. Moreover, technologies for safe disposal of epidermal electronics (most of which eventually end up in electronic wastes) have been rarely explored. Furthermore, harsh and fluctuating conditions during prolonged outdoor activities may affect the accuracy and reliability of those skin-mounted devices. [3,4] Most designs neglect these important aspects of epidermal devices, hindering them from real-world applications.Here we report a set of degradable epidermal electronics consisting of both physical and biochemical sensors that can monitor multidimensional physiological parameters such as electrocardiograms (ECG), electrooculography (EOG), and electromyography (EMG) as well as temperature, strain, humidity, and bacterial infection. Using an artificial neural network (ANN), important physiology signatures can be detected that are nearly unaffected by individual differences. Moreover, while Epidermal sensing devices offer great potential for real-time health and fitness monitoring via continuous characterization of the skin for vital morphological, physiological, and metabolic parameters. However, peeling them off can be difficult and sometimes painful especially when these skinmounted devices are applied on sensitive or wounded regions of skin due to their strong adhesion. A set of biocompatible and water-decomposable "skinfriendly" epidermal electronic devices fabricated on flexible, stretchable, and degradable protein-based substrates are reported. Strong adhesion and easy detachment are achieved concurrently through an environmentally benign, plasticized protein platform offering engineered mechanical properties and water-triggered, on-demand decomposition lifetime (transiency). Human experiments show that multidimensional physiological signals can be measured using these innovative epidermal devices consisting of electroand biochemical sensing modules and analyzed for important physiological signatures using an artificial neural network. The advances provide unique, versatile capabilities and broader applications for user-and environmentally friendly epidermal devices.Epidermal electronics, an emerging class of wearable electronic devices that are mounted on the human skin with conformal contact for direct skin-sensor interactions, are especially appealing for the "Internet of Things" and next-generation wearable medical applications. [1][2][3][4][5]...

A Bioinspired Wireless Epidermal Photoreceptor for Artificial Skin Vision

“…From the point of biomimetic view, the ASV is constituted of light filter, light sensor, and signal conduction units, mimicking the hierarchical structure of natural rod cells. In detail, the device consists of three subsystems separated by thin encapsulations,: i) a skin‐friendly silk‐based adhesive layer for stable, strong, and seamless adhesion to skin tissues without signs of a rash in a manner that offers biocompatibility with skin, even in regions covered with hairs or in the presence of sweat; [ 25 ] ii) an encapsulated collection of flexible optoelectronic layers, an interdigital electrode, and a wireless coil, functioning as a light sensor and signal conduction unit for on‐skin optical imaging and wireless readout; and iii) a sealed liquid reservoir with a customizable functional light filter and a set of microchannel arrays directly connecting skin tissues to the reservoir for sweat collection.…”

“…Natural skin vision systems will permit a new class of ASV devices and systems to be designed; however, challenges remain in terms of reliable manufacturing and multilevel system integration/packaging of robust light filters, flexible light sensors, wireless signal readout units, skin‐friendly substrates, as well as efficient signal processing and analysis algorithms. [ 20–25 ]…”

Soft Electronics for the Skin: From Health Monitors to Human–Machine Interfaces

“…[83,84] Tao et al innovated a highly flexible and skinadhesive substrate based on a combination of silk and resilin proteins which simultaneously imparted strong adhesion, easy detachment, tunable mechanical properties, and water-triggered on-demand decomposition lifetime. [85]…”

Mechanical Tolerance of Cascade Bioreactions via Adaptive Curvature Engineering for Epidermal Bioelectronics

“…[ 5–8 ] One necessity as well as a challenge for epidermal bioelectronics is mechanical tolerance, that is, the ability to withstand mechanical deformations, which is a vital parameter to preserve signal fidelity in an inherent dynamic and stretchable epidermal system. [ 9–13 ] While mechanical tolerance has been demonstrated in monitoring electrophysiological signals, [ 14–16 ] it is more challenging to achieve mechanically tolerant biosensors that convert biochemical information to detectable signals, due to the difficulty in realizing invariance of surface bioreactions under deformation. Developing rigid biosensing area integrated with stretchable connectors has been proven as one way to circumvent this difficulty.…”