Issue 21, 2024

A highly conductive, robust, self-healable, and thermally responsive liquid metal-based hydrogel for reversible electrical switches

Abstract

This study introduces a thermally responsive smart hydrogel with enhanced electrical properties achieved through volume switching. This advancement was realized by incorporating multiscale liquid metal particles (LMPs) into the PNIPAM hydrogel during polymerization, using their inherent elasticity and conductivity when deswelled. Unlike traditional conductive additives, LMPs endow the PNIPAM hydrogel with a remarkably consistent volume switching ratio, significantly enhancing electrical switching. This is attributed to the minimal nucleation effect of LMPs during polymerization and their liquid-like behavior, like vacancies in the polymeric hydrogel under compression. The PNIPAM/LMP hydrogel exhibits the highest electrical switching, with an unprecedented switch of 6.1 orders of magnitude. Even after repeated swelling/deswelling cycles that merge some LMPs and increase the conductivity when swelled, the hydrogel consistently maintains an electrical switch exceeding 4.5 orders of magnitude, which is still the highest record to date. Comprehensive measurements reveal that the hydrogel possesses robust mechanical properties, a tissue-like compression modulus, biocompatibility, and self-healing capabilities. These features make the PNIPAM/LMP hydrogel an ideal candidate for long-term implantable bioelectronics, offering a solution to the mechanical mismatch with dynamic human tissues.

Graphical abstract: A highly conductive, robust, self-healable, and thermally responsive liquid metal-based hydrogel for reversible electrical switches

Supplementary files

Article information

Article type
Paper
Submitted
01 Feb 2024
Accepted
17 Apr 2024
First published
03 May 2024

J. Mater. Chem. B, 2024,12, 5238-5247

A highly conductive, robust, self-healable, and thermally responsive liquid metal-based hydrogel for reversible electrical switches

J. H. Lee, J. E. Hyun, J. Kim, J. Yang, H. Zhang, H. Ahn, S. Lee, J. H. Kim and T. Lim, J. Mater. Chem. B, 2024, 12, 5238 DOI: 10.1039/D4TB00209A

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