Combustion‐Assisted Photonic Sintering of Printed Liquid Metal Nanoparticle Films

Abstract

Liquid metals are ideally suited for flexible and wearable electronics due to their compatibility with additive manufacturing and high electrical conductivity that is maintained following mechanical perturbation. While printing of eutectic gallium–indium (eGaIn) liquid metal nanoparticles has been demonstrated, previous techniques for activating electrical conductivity in the as‐printed insulating eGaIn nanoparticles limit throughput in roll‐to‐roll manufacturing processes. Here, ultrafast photonic sintering of eGaIn nanoparticles is demonstrated, which is further enhanced through the use of nitrocellulose as a carrier polymer that undergoes optically triggered combustion to produce eGaIn thin films with electrical conductivities exceeding 104 S cm–1. This combustion‐assisted photonic sintering (CAPS) is two orders of magnitude faster than previously demonstrated noncontact sintering techniques. By circumventing the established tradeoff between electrical conductivity and activation speed, CAPS will facilitate the use of eGaIn liquid metal nanoparticles in high‐throughput additive manufacturing of flexible and wearable electronics, sensors, and related technologies.

Nanoarchitectonics and Applications of Gallium‐Based Liquid Metal Micro‐ and Nanoparticles

“…The GLM micro-nanoparticles are sintered using combustion-assisted photons. [52] Using this method, the GLM nanoparticles can be sintered in a large area, and the sintering speed is two orders of magnitude faster than the previously proven non-contact sintering technology. Nitrocellulose is a polymer derivative of nitrocellulose, which can be burned exothermically, and has been proved to be effective in dispersing nanomaterials and producing uniform films.…”

“…The GLM micro‐nanoparticles are sintered using combustion‐assisted photons [52] . Using this method, the GLM nanoparticles can be sintered in a large area, and the sintering speed is two orders of magnitude faster than the previously proven non‐contact sintering technology.…”

“…This method can be used to produce conductive circuits with higher resolution. The sintering process of GLM can be realized by different methods, such as high temperature sintering, [50] mechanical pressure sintering, [51] acoustic wave sintering, [24] combustion assisted photon sintering, [52] etc. Sintering can be completed in milliseconds to minutes.…”

3D Printing of Liquid Metals: Recent Advancements and Challenges

“…[86][87][88] Initially, the printed features are non-conductive; therefore, comparable techniques are required to activate the conductivity. [89] In general, EGaIn nanoparticle films are processed by laser or thermal sintering. [90] Both methods transfer heat energy to the film and produce thermal stress in the particles, resulting in the cracking of the gallium oxide shell and enhancement of conductivity on the entire film.…”

Tough Bonding of Liquid Metal‐Elastomer Composites for Multifunctional Adhesives

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Recently, soft composites consisting of liquid metal (LM) droplets dispersed in highly deformable elastomers have gained particular interest, as these materials are soft and stretchable yet display exceptional mechanical, thermal, and electrical properties. [9][10][11][12][13][14][15][16][17][18][19] For example, LM composites can act as soft wiring for wearable devices, yet be flexible enough to seamlessly interface with the contours of human tissue. [20][21][22][23][24] Liquid metal and LM composites are also useful as thermal interface materials (TIMs) for electronic components to improve heat dissipation.

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