Programmable Microfluidic-Assisted Highly Conductive Hydrogel Patches for Customizable Soft Electronics

The use of hydrogels in soft electronics has advanced the development of wearable and implantable devices, but challenges remain, such as balancing stretchability and electrical conductivity, miniaturization difficulties, and dehydration susceptibility. This study introduces a lignin-polyacrylamide (Ag-LPA) hydrogel composite that features anti-freeze properties, self-adhesion, excellent water retention, and high stretchability (1072%). It demonstrates impressive electrical conductivity at both room temperature (47.924 S cm⁻¹) and extremely cold temperatures (42.507 S cm⁻¹). The composite is designed for microfluidic-assisted hydrogel patches (MAHPs), enhancing water retention and versatility in packaging materials, making it suitable for durable soft electronics applications. Various prototypes, including healthcare monitoring, environmental temperature sensing, and 3D-spring pressure monitoring electronics, were successfully developed. The Ag-LPA hydrogel's conductivity suggests potential applications in polar rescue missions. Overall, MAHPs are expected to significantly advance tailored soft electronics, opening new possibilities in engineering applications.

For more info, DOI: https://doi.org/10.1002/adfm.202401930

Synthesis of Ag-LPA hydrogel composite and its electromechanical and electro-stability characterization. a) Synthesis routine of Ag-LPA hydrogel composite. a (i). SEM image illustrating the micromorphology of the Ag-LPA hydrogel composite. a (ii). EDS analysis of the GDP of the Ag flakes. Scale bar = 50 µm. b) Optical images of the 8% Ag-LPA hydrogel composite stretching to over 1000% in the tensile testing. c) Stress–strain curves of 6%, 8%, 10% 12% Ag-LPA hydrogel composite and calculated the Young's modulus for each Ag flake content (inset). N = 3 samples. d) Resistance stability of the 8% Ag-LPA hydrogel composite. d (i). Resistance stability under 100% mechanical strains to 1000 cycles. d (ii). Resistance changes under 100% mechanical strains for the first 10 cycles. d (iii). Resistance changes under 100% mechanical strains for the last 10 cycles. e) Water loss of the Ag-LPA hydrogel composite under high-temperature evaporation conditions (70 °C). f) The resistance changes of the Ag-LPA hydrogel composite under 100% mechanical strains at room temperature and temperature of −20 °C. g) Resistance stability of sharp changes in temperature from room temperature to a temperature of −20 °C. h) Conductivity of Ag-LPA hydrogel composite at room temperature and a temperature of −20 °C.