Ultrasonic‐Enabled Nondestructive and Substrate‐Independent Liquid Metal Ink Sintering

Abstract

Printing or patterning particle‐based liquid metal (LM) ink is a good strategy to overcome poor wettability of LM for its circuits’ preparation in flexible and printed electronics. Subsequently, a crucial step is to recover conductivity of LM circuits consisting of insulating LM micro/nano‐particles. However, most widely used mechanical sintering methods based on hard contact such as pressing, may not be able to contact the LM patterns' whole surface conformally, leading to insufficient sintering in some areas. Hard contact may also break delicate shapes of the printed patterns. Hereby, an ultrasonic‐assisted sintering strategy that can not only preserve original morphology of the LM circuits but also sinter circuits on various substrates of complex surface topography is proposed. The influencing factors of the ultrasonic sintering are investigated empirically and interpreted with theoretical understanding by simulation. LM circuits encapsulated inside soft elastomer are successfully sintered, proving feasibility in constructing stretchable or flexible electronics. By using water as energy transmission medium, remote sintering without any direct contact with substrate is achieved, which greatly protect LM circuits from mechanical damage. In virtue of such remote and non‐contact manipulation manner, the ultrasonic sintering strategy would greatly advance the fabrication and application scenarios of LM electronics.

Magnetically Responsive Gallium-Based Liquid Metal: Preparation, Property and Application

“…The liquid metal droplets can be controlled as miniature components within microfluidic system including pump, valve, electrode, and mixer. 162 In comparison to electronic field, 163 ultrasound 164 and pneumatic systems, 165 magnetic manipulation can achieve accurate and on-demand movement. Therefore, the advancement of MRLM in microfluidics contributes to the construction of a customized chip laboratory with a controllability.…”

Acidic-Induced Liquid Metal–Montmorillonite Self-Sintering Conductive Ink with Multilayer Sandwiched Structure for Flexible Printed Electronics

“…19 Although the encapsulation of liquid metal nanoparticles (LMNPs) through an organic shell layer could improve their stable dispersion, 21−24 the conductivity would be impaired, making the extra sintering of the ink necessary. 20,25 The widely used sintering strategies including mechanical force, 26,27 laser etching, 28 ultrasonication, 29 and cryogenic phase change 30 protective shell of the LMNPs to release the internal LM fluid, forming a connected conductive path. Nevertheless, these external sintering methods can hardly be quantitatively and accurately applied, probably leading to certain damage to the pattern or substrate and particularly affecting the performance and standardization of LM-based electronic devices.…”

“…The widely used sintering strategies including mechanical force, , laser etching, ultrasonication, and cryogenic phase change are all aimed at externally rupturing the protective shell of the LMNPs to release the internal LM fluid, forming a connected conductive path. Nevertheless, these external sintering methods can hardly be quantitatively and accurately applied, probably leading to certain damage to the pattern or substrate and particularly affecting the performance and standardization of LM-based electronic devices.…”

Ultrasound Powered Wetting and Filling of Liquid Metal into Ultrafine Channels for Flexible Electronics

“…Considerable approaches have been explored to prepare and pattern LM circuits on various soft substrates for exible electronics, which can be broadly divided into two categories, i.e., direct and indirect strategies. The former includes direct ink writing 5,22 , lithography-enabled patterning 21,23 , 3D printing [24][25][26] and subtractive ablation 27,28 , which selectively deposit LMs at desired locations on the substrate, usually followed by sealed packaging with polymeric elastomers. Due to the intrinsically high surface tension, LMs are non-wettable to most soft substrate materials used in exible electronics.…”