Healable, Recyclable, and Multifunctional Soft Electronics Based on Biopolymer Hydrogel and Patterned Liquid Metal

Abstract

Recent years have witnessed the rapid development of sustainable materials. Along this line, developing biodegradable or recyclable soft electronics is challenging yet important due to their versatile applications in biomedical devices, soft robots, and wearables. Although some degradable bulk hydrogels are directly used as the soft electronics, the sensing performances are usually limited due to the absence of distributed conducting circuits. Here, sustainable hydrogel‐based soft electronics (HSE) are reported that integrate sensing elements and patterned liquid metal (LM) in the gelatin–alginate hybrid hydrogel. The biopolymer hydrogel is transparent, robust, resilient, and recyclable. The HSE is multifunctional; it can sense strain, temperature, heart rate (electrocardiogram), and pH. The strain sensing is sufficiently sensitive to detect a human pulse. In addition, the device serves as a model system for iontophoretic drug delivery by using patterned LM as the soft conductor and electrode. Noncontact detection of nearby objects is also achieved based on electrostatic‐field‐induced voltage. The LM and biopolymer hydrogel are healable, recyclable, and degradable, favoring sustainable applications and reconstruction of the device with new functions. Such HSE with multiple functions and favorable attributes should open opportunities in next‐generation electronic skins and hydrogel machines.

Liquid Metal Patterning and Unique Properties for Next‐Generation Soft Electronics

“…When LM is utilized with other recyclable materials, entirely recyclable electronics become feasible. [118] Several studies on recyclable LM-based circuits have been conducted. [39,114b] For example, Li et al proposed an LM paper composed of cellulose nanofibrils, PVA, and LM by casting them into a mold.…”

Bio‐inspired ionic skins for smart medicine

“…One possible opportunity is to develop circuit boards based on liquid metals and stretchable semiconductive polymers. [97][98][99][100][101] However, the emergence of electric-double-layer interfaces in ionic skin systems may increase power consumption and decrease efficiency. In contrast, the biological system combines the intelligence of stimuli perception, signal transmission, signal processing, and information storage.…”

“…On the other hand, the data processing and storage components for the ionic skins are mainly based on conventional printed circuit boards and rigid semiconductor electronics, causing extra burdens for the ionic skin systems. One possible opportunity is to develop circuit boards based on liquid metals and stretchable semiconductive polymers 97–101 . However, the emergence of electric‐double‐layer interfaces in ionic skin systems may increase power consumption and decrease efficiency.…”

Smart Eutectic Gallium–Indium: From Properties to Applications

“…Flexible and stretchable electronics play an important role in the development of sensors, [240][241][242][243][244] antenna, [245,246] electronic circuits, [74,247] and area which is a natural fit for liquid metals. This section reviews the recent developments of flexible and stretchable electronics based on liquid metals, and we discuss the opportunities as well as challenges for this new generation of soft electronic devices.…”