Liquid alloy printing of microfluidic stretchable electronics

Abstract

Recently, microfluidic stretchable electronics has attracted great interest from academia since conductive liquids allow for larger cross-sections when stretched and hence low resistance at longer lengths. However, as a serial process it has suffered from low throughput, and a parallel processing technology is needed for more complex systems and production at low costs. In this work, we demonstrate such a technology to implement microfluidic electronics by stencil printing of a liquid alloy onto a semi-cured polydimethylsiloxane (PDMS) substrate, assembly of rigid active components, encapsulation by pouring uncured PDMS on-top and subsequent curing. The printing showed resolution of 200 μm and linear resistance increase of the liquid conductors when elongated up to 60%. No significant change of resistance was shown for a circuit with one LED after 1000 times of cycling between a 0% and an elongation of 60% every 2 s. A radio frequency identity (RFID) tag was demonstrated using the developed technology, showing that good performance could be maintained well into the radio frequency (RF) range.

A skin-attachable, stretchable integrated system based on liquid GaInSn for wireless human motion monitoring with multi-site sensing capabilities

“…30,31 Various techniques have been developed to pattern liquid metals, including the injection method, stencil lithography, inkjet printing, micro-textured surface enabled patterning and selective wetting. [31][32][33][34][35] Figure 2 (a-c) Contact angle images of the GaInSn droplet on various substrates of (a) PDMS, (b) Au deposited glass substrate and (c) Au deposited PDMS substrate. Each image shows dramatic changes in contact angle before (al, b1 and c1) and after (a2, b2 and c2) reducing its surface with 10 wt% NaOH.…”

Fast Fabrication of Flexible Functional Circuits Based on Liquid Metal Dual‐Trans Printing

“…For these reasons, the liquid metal has been increasingly investigated as an excellent electronic material for making stretchable antennas, [ 12 ] bioelectrodes, [ 13 ] capacitors and inductors, [ 14 ] strain sensor, [ 15 ] pressure sensor, [ 16 ] curvature sensor, [ 17 ] micropump, [ 18 ] and so on. Meanwhile, various techniques that targeted for patterning the liquid metal have also been put forward, such as inkjet printing, [ 19,20 ] microfl uidic channel injection, [ 21,22 ] masked deposition, [23][24][25] imprinting, [ 26 ] microcontact printing, [ 27 ] stamp lithography, [ 27 ] 3D printing, [ 28,29 ] and direct writing, [30][31][32][33][34] etc. Using lithographic or droplet-based strategies, each of these techniques has displayed rather distinctive merits and demonstrated their promising potentials for many electrical use purposes.…”

From stretchable to reconfigurable inorganic electronics

“…Other groups have also fabricated liquid-metal patterns through screen-printing and embedding techniques [97,98] (Figure 4a), where electrical resistance changes with mechanical deformation of the liquid metal upon stretching. Although the fluidity of liquid metals provides durability under large applied strains, it can be also seen as a limitation, especially for micropatterning when detailed features would not be properly resolved.…”