Aerosol Spray Deposition of Liquid Metal and Elastomer Coatings for Rapid Processing of Stretchable Electronics

Abstract

We report a spray deposition technique for patterning liquid metal alloys to form stretchable conductors, which can then be encapsulated in silicone elastomers via the same spraying procedure. While spraying has been used previously to deposit many materials, including liquid metals, this work focuses on quantifying the spraying process and combining it with silicones. Spraying generates liquid metal microparticles (~5 μm diameter) that pass through openings in a stencil to produce traces with high resolution (~300 µm resolution using stencils from a craft cutter) on a substrate. The spraying produces sufficient kinetic energy (~14 m/s) to distort the particles on impact, which allows them to merge together. This merging process depends on both particle size and velocity. Particles of similar size do not merge when cast as a film. Likewise, smaller particles (<1 µm) moving at the same speed do not rupture on impact either, though calculations suggest that such particles could rupture at higher velocities. The liquid metal features can be encased by spraying uncured silicone elastomer from a volatile solvent to form a conformal coating that does not disrupt the liquid metal features during spraying. Alternating layers of liquid metal and elastomer may be patterned sequentially to build multilayer devices, such as soft and stretchable sensors.

Applications of liquid metals in nanotechnology

“…Alternatively, spraying process of LM can generate sufficient kinetic energy to merge the LM droplets on impact producing conductive paths. 167 The insulating nature of the LM nanodroplets can constitute an advantage for soft electronic device fabrication. As an example, the selective mechanical merging of LM nanodroplets allows for the formation of tunable antennas for wireless communication.…”

Liquid Metal-Based Devices: Material Properties, Fabrication and Functionalities

“…The fabrication technology of LM includes 3-D printing [25][26][27][28], soft lithography [31,32] and spray printing [4][5][6]. To manufacture complex three-dimensional antennas, a cavity can be made by 3-D printing, and the pressure difference used to push the metal into the cavity [25].…”

“…Although spraying technology has been used to deposit many materials, Ref. [6] reported a spray deposition technology that allowed LM alloys to form stretchable conductors that were encapsulated in silicone elastomers. The focus of this work was the quantitative spraying process and combining it with silicone.…”

“…In the EGaIn thin line pattern production method based on soft lithography technology, the size of the produced thin lines can be scalable, uniform and without residue, and the line width on the same soft substrate can be from a single micron to a few millimeters [3]. Spray printing can be directly applied to various substrates, and liquid metal droplets can be sprayed on the cloth substrate [4], sprayed and wiped on the PDMS substrate [5], or quantitatively sprayed and packaged in silicone elastomer in combination with silicone [6].…”

Modification of the Mechanical Properties of Core‐Shell Liquid Gallium Nanoparticles by Thermal Oxidation at Low Temperature

“…In addition, liquid metals possess the ability to be patterned into nonspherical shapes using different methods to form highly conductive and durable interconnects with direct application in microfluidics and soft, flexible, and stretchable electronics. [9][10][11][12][13] For the latter application, it becomes essential to control the mechanical properties of these coreshell NPs.…”