Nanofabrication for all-soft and high-density electronic devices based on liquid metal

Min-Gu Kim,Devin K Brown,Oliver Brand

doi:10.1038/s41467-020-14814-y

Min-Gu Kim, Devin K Brown + Show 1 more

Open Access

https://doi.org/10.1038/s41467-020-14814-y

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Abstract

Innovations in soft material synthesis and fabrication technologies have led to the development of integrated soft electronic devices. Such soft devices offer opportunities to interact with biological cells, mimicking their soft environment. However, existing fabrication technologies cannot create the submicron-scale, soft transducers needed for healthcare and medical applications involving single cells. This work presents a nanofabrication strategy to create submicron-scale, all-soft electronic devices based on eutectic gallium-indium alloy (EGaIn) using a hybrid method utilizing electron-beam lithography and soft lithography. The hybrid lithography process is applied to a biphasic structure, comprising a metallic adhesion layer coated with EGaIn, to create soft nano/microstructures embedded in elastomeric materials. Submicron-scale EGaIn thin-film patterning with feature sizes as small as 180 nm and 1 μm line spacing was achieved, resulting in the highest resolution EGaIn patterning technique to date. The resulting soft and stretchable EGaIn patterns offer a currently unrivaled combination of resolution, electrical conductivity, and electronic/wiring density.

Highlights

Innovations in soft material synthesis and fabrication technologies have led to the development of integrated soft electronic devices
Innovations in soft functional material synthesis and fabrication technologies have led to the development of integrated soft electronic devices for applications in human organs-on-chips as well as skin- or body-integrated electronics with material interfaces that are better matched from a mechanical properties point of view[6,7,8,9]
Building on our initial work[50], this paper describes a nanofabrication strategy to create submicron-scale, all-soft electronic devices based on eutectic gallium-indium alloy (EGaIn)

Summary

Introduction

Innovations in soft material synthesis and fabrication technologies have led to the development of integrated soft electronic devices. In design-focused approaches, compliant two-dimensional (2D) serpentine or three-dimensional (3D) helical patterns are formed from solid metal thin films on soft substrates to endure mechanical deformation[14,15,16] These engineered 2D/3D network architectures can interface with biological materials over large areas. Material-focused approaches utilize elastic conductors based on conductive nanomaterials that are either embedded into polymer matrices or dispensed directly onto a soft substrate[19,20,21] These printing approaches enable inexpensive fabrication processes for conductive circuits without the need of serpentine geometries, but the relatively low resolution (50–150 μm for conventional printing methods19–21) and low conductivity (

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