Monolithically Programmed Stretchable Conductor by Laser‐Induced Entanglement of Liquid Metal and Metallic Nanowire Backbone

Abstract

Owing to its low mechanical compliance, liquid metal is intrinsically suitable for stretchable electronics and future wearable devices. However, its invariable strain‐resistance behavior according to the strain‐induced geometrical deformation and the difficulty of circuit patterning limit the extensive use of liquid metal, especially for strain‐insensitive wiring purposes. To overcome these limitations, herein, novel liquid‐metal‐based electrodes of fragmented eutectic gallium‐indium alloy (EGaIn) and Ag nanowire (NW) backbone of which their entanglement is controlled by the laser‐induced photothermal reaction to enable immediate and direct patterning of the stretchable electrode with spatially programmed strain‐resistance characteristics are developed. The coexistence of fragmented EGaIn and AgNW backbone, that is, a biphasic metallic composite (BMC), primarily supports the uniform and durable formation of target layers on stretchable substrates. The laser‐induced photothermal reaction not only promotes the adhesion between the BMC layer and substrates but also alters the structure of laser‐irradiated BMC. By controlling the degree of entanglement between fragmented EGaIn and AgNW, the initial conductivity and local gauge factor are regulated and the electrode becomes effectively insensitive to applied strain. As the configuration developed in this study is compatible with both regimes of electrodes, it can open new routes for the rapid creation of complex stretchable circuitry through a single process.

Nanowire-assisted freestanding liquid metal thin-film patterns for highly stretchable electrodes on 3D surfaces

“…This phenomenon is defined as multiphase sintering in this research article. As the laser is exposed to the composite film of LM and AgNW, LM undergoes small explosion and the liquid core covers the AgNW due to the capillary force and the metallic binding force between them 22 , where other LM coalesces together. These results of coalescence between the two with enhanced interaction can be seen as gross coalescing in Fig.…”

Liquid Metal Patterning and Unique Properties for Next‐Generation Soft Electronics

“…Additive DW originates from the engineering desire to draw complex electrically conducting patterns using a mere pen similar to conventional art sketching. [ 48 ] One intuitive DW method is drawing with a roller‐ball pen, which was presented by Zheng et al The group directly wrote an LM circuit with the pen onto a flexible polymer, forming an electronic device. The width and thickness of the pattern were as low as 200 and 80 µm, respectively.…”

Toward a new generation of permeable skin electronics

“…The sensor showed an extremely low detection limit (2 μM) and superior sensitivity (8.51 mA cm −2 mM −1 ). 56 Besides, metal nanowire percolation networks are promising electrodes components, including AgNWs network electrodes [57][58][59][60][61] and CuNWs electrodes. [62][63][64][65][66] Their ultra-thin thickness, porosity, and high conductivity demonstrate great potential for developing gas-permeable skin-mountable electronics.…”