Solvent-Assisted Filling of Liquid Metal and Its Selective Dewetting for the Multilayered 3D Interconnect in Stretchable Electronics

Abstract

As stretchable electronics are rapidly developing and becoming complex, the requirement for stretchable, multilayered, and large-area printed circuit boards (PCBs) is emerging. This demands a stretchable electrode and its vertical interconnect access (via) for 3-dimensional (3D) connectivity between layers. Here, we demonstrate solvent-assisted liquid metal (LM) filling into the submicrometer channel (∼400 nm), including via-hole filling and selective dewetting of LM. We provide the theoretical background of solvent-assisted LM filling and selective dewetting and reveal the osmotic pressure arising from anomalous mass transport phenomena, case II diffusion, which drives negative pressure, the spontaneous pulling of LM into the open channel. Also, we suggest design criteria for the geometry and dimension of LM interconnects to obtain structural stability without dewetting, based on the theoretical and computational background. We demonstrate a simple stretchable near-field communication (NFC) device including transferred micrometer-size light-emitting diodes (LEDs) with only 230 μm to the stretchable liquid metal PCB, without any soldering process. The device operates stably under repetitive stretching and releasing (∼50% uniaxial strain) due to the stable connection through the LM via between the upper and lower layers. Finally, we propose a concept for modular-type stretchable electronics, based on the cohesive liquid nature of LM. As a building block, the functional module can be easily removed from a mainframe, and replaced by another functional module, to suit user demand.

Bio‐Inspired Differential Capillary Migration of Aqueous Liquid Metal Ink for Rapid Fabrication of High‐Precision Monolayer and Multilayer Circuits

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Breathable and Stretchable Multifunctional Triboelectric Liquid‐Metal E‐Skin for Recovering Electromagnetic Pollution, Extracting Biomechanical Energy, and as Whole‐Body Epidermal Self‐Powered Sensors

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Liquid Metal Combinatorics toward Materials Discovery

“…In addition, organic solvents can be introduced into the substrate for the selective infiltration of liquid metals and modulation of structural elements. [ 159 ]…”

“…In addition, organic solvents can be introduced into the substrate for the selective infiltration of liquid metals and modulation of structural elements. [159] Filling Microchannel with Liquid Metals: The desired liquid metal conductive network can be obtained within the elastomer by injecting liquid metal under positive or negative pressure into a designed microfluidic channel [160] (Figure 7b). Elastomers with microchannels are typically obtained using techniques such as photolithography and molding.…”