Liquid Metal–Based Soft Microfluidics

Abstract

Motivated by the increasing demand of wearable and soft electronics, liquid metal (LM)‐based microfluidics has been subjected to tremendous development in the past decade, especially in electronics, robotics, and related fields, due to the unique advantages of LMs that combines the conductivity and deformability all‐in‐one. LMs can be integrated as the core component into microfluidic systems in the form of either droplets/marbles or composites embedded by polymer materials with isotropic and anisotropic distribution. The LM microfluidic systems are found to have broad applications in deformable antennas, soft diodes, biomedical sensing chips, transient circuits, mechanically adaptive materials, etc. Herein, the recent progress in the development of LM‐based microfluidics and their potential applications are summarized. The current challenges toward industrial applications and future research orientation of this field are also summarized and discussed.

Designing “Supermetalphobic” Surfaces that Greatly Repel Liquid Metal by Femtosecond Laser Processing: Does the Surface Chemistry or Microstructure Play a Crucial Role?

“…Then, the liquid mixture was cured at 80 °C for 2 h. The typical EgaIn (70% Ga & 30% In) (Shuochen Metal Co., Ltd., China) droplet was adopted in the experiment as the LM. Liquid EGaIn has the melting point of ≈15.5 °C, surface tension of ≈624 × 10 −3 N m −1 , viscosity of ≈1.99 × 10 −3 Pa∙s, conductivity of ≈3.40 × 10 6 S m −1 , thermal conductivity of ≈26.6 W m −1 K −1 , and density of 6.28 g cm −3 71…”

“…Liquid EGaIn has the melting point of ≈15.5 °C, surface tension of ≈624 × 10 −3 N m −1 , viscosity of ≈1.99 × 10 −3 Pa•s, conductivity of ≈3.40 × 10 6 S m −1 , thermal conductivity of ≈26.6 W m −1 K −1 , and density of 6.28 g cm −3 . [71] Femtosecond Laser Treatment: FsL was applied to generate microstructure on the sample surfaces. The sample was previously fixed on a moveable platform.…”

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

“…[34] In addition to imparting flexibility to electronic devices, they also require mechanical stretchability to better interface and concurrently deform with the skin. Two strategies have been applied to achieve mechanical stretchability in soft electronics: 1) utilizing intrinsically stretchable, rubbery materials including rubbery electronic materials (semiconductors, conductors, and dielectrics) [14,15,24,[35][36][37][38][39][40][41][42][43][44][45] and liquid metals [46][47][48][49] to build the electronics; 2) employing engineered structures like wrinkles, [34,[50][51][52][53][54][55][56] serpentines, [12,17,33,44,[57][58][59][60][61] island-bridge structures, [62,63] textiles, [64] origami, [65,66] kirigami, [37,67] and microcracks [68] to accommodate the induced strain. [30,…”

Liquid metal nanocomposites

“…Metals that are liquid at room temperature have the potential for transformative impact in applications that depend on combining high electrical or thermal conductivity with extreme mechanical compliance and deformability. 1 Over the past decade, liquid metal (LM) alloys like eutectic gallium-indium (EGaIn) and gallium-indium-tin (Galinstan) have been shown to provide a unique functional role in applications ranging from so and stretchable "second skin" electronics for wearable sensing [2][3][4] to stimuli-responsive actuators capable of eldcontrolled motion and reversible shape change [5][6][7] and intracellular drug delivery. 8 Such applications of LM in wearable electronics, so robotics, and nanomedicine have largely focused on ways to encapsulate the liquid so that it can remain intact during interaction with other materials.…”

“…He leads a research group dedicated to creating materials that match the extraordinary adaptability, rich multi-functionality, and embodied intelligence of natural material systems by bridging the gap between nanoscale engineering and system-level functionality. He received his PhD at the University of Florida, had a postdoctoral fellowship at the elastomer remains a popular approach, 2,4 there has been increasing interest in material systems composed of a suspension of LM droplets that are either isolated from each other or connected to form electrically conductive pathways. 9,10 In recent years, these latter efforts have merged with practices in LMbased nanotechnology 11 to enable a new domain of research on the topic of liquid metal nanocomposites.…”