Ga-Based Liquid Metals: Versatile and Biocompatible Solutions for Next-Generation Bioelectronics

Abstract

The utilization of gallium (Ga)-based liquid metals (LMs) as functional materials in bioelectronics has been extensively explored over the past decade as a key to stimulation of biological systems and recording of biological signals. The motivation behind this class of electronics is driven by the opportunities to exploit mechanical properties similar to biological tissues. These bioelectronic devices are required to maintain functionality under deformation and, especially for implantable applications, should interface with biological tissues in a minimally invasive manner. LMs are attractive for such applications due to their ability to deform while retaining their electrical conductivity. Furthermore, unlike most liquids that form droplets to minimize surface energy, the ultrathin solid-state oxide layer on the outer surface of LMs enables them to be shaped to specific 3D patterns. Unlike mercury, Ga-based LMs are considered biocompatible due to their low toxicity and vapor pressure, highlighting their potential as advantageous materials for bioelectronics. This review comprehensively presents the fundamental aspects of these materials, with a focus on their effectiveness in stimulating and recording specific biological tissues, as well as their diverse applications as soft and stretchable electrodes in bioelectronics. Additionally, this review investigates additional strategies aimed at driving future advancements in this field.