Robust and Multifunctional Liquid-Metal Embedded Elastomers for Ultrastretchable Electronics: a Short Review

Abstract: Soft electronics are a promising and revolutionary alternative for traditional electronics when safe physical interaction between machines and the human body is required. Among various materials architectures developed for producing soft and stretchable electronics, Liquid-Metal Embedded Elastomers (LMEEs), which contain Ga-based inclusions as a conductive phase, has drawn considerable attention in various emerging fields such as wearable computing and bio-inspired robotics. This is because LMEEs exhibit a unique combination of desirable mechanical, electrical, and thermal properties. For instance, these so-called multifunctional materials can undergo large deformations as high as 600% strain without losing their electrical conductivity. Moreover, the desperation of conductive liquid-metal inclusions within the entire medium of an elastomer makes it possible to fabricate autonomously self-healing circuits that maintain their electrical functionality after extreme mechanical damage induction. The electrically self-healing property is of great importance for further progress in autonomous soft robotics, where materials are subjected to various modes of mechanical damage such as tearing. In this short review, we review the fundamental characteristics of LMEEs, their advantages over other conductive composites, materials used in LMMEs, their preparation and activation process, and the fabrication process of self-healing circuits. Additionally, we will review the soft-lithography-enabled techniques for liquid-metal pattering.