Solvent-free synthesis and processing of conductive elastomer composites for "green" dielectric elastomer transducers

Stretchable electrodes are the more suitable for dielectric elastomer transducers (DET), the closer the mechanical characteristics of electrodes and elastomer are. Here, we present a solvent-free synthesis and processing of conductive composites with excellent electrical and mechanical properties for transducers. The composites are prepared by in-situ polymerization of cyclosiloxane monomers in the presence of graphene nanoplatelets. The low viscosity of the monomer allows for easy dispersion of the filler, eliminating the need for a solvent. After the polymerization, a cross-linking agent is added at room temperature, the composite is solvent-free screen-printed, and the cross-linking reaction is initiated by heating. The best material shows conductivity σ = 8.2 S∙cm^-1 , Young's modulus Y_10% = 167 kPa, and strain at break s = 305%. The electrode withstands large uniaxial strains without delamination, shows no conductivity losses during repeated operation for 500 000 cycles, and has an excellent recovery of electrical properties upon being stretched at strains of up to 180%. Reliable prototype capacitive sensors and stack actuators are manufactured by screen-printing the conductive composite on the dielectric film. Finally, stack actuators manufactured from dielectric and conductive materials that are synthesized solvent-free are demonstrated. The stack actuators even self-repair after a breakdown event. This article is protected by copyright. All rights reserved.

Stretchable gold fiber-based wearable textile electrochemical biosensor for lactate monitoring in sweat

Past several years have witnessed growing interest in developing wearable biosensors for non-invasive monitoring vital signs of chemical/biological markers such as lactate. In this context, textiles can be seen as a promising platform for the integration of wearable chemical sensors due to their inherent breathability, flexibility, softness and comfortableness. Gold is regarded as a preferred active sensing material due to its excellent biocompatibility, chemical inertness and wide electrochemical window. Here, a dry-spinning method was used to fabricate stretchable, strain-insensitive and highly conductive gold fibers. Such gold fibers could be used to fabricate lactate-sensing working electrodes, reference electrode, counter electrodes and further weaved into textiles in a standard three-electrode system with a planar layout. The textile lactate biosensors showed a high sensitivity of 19.13 μA/mM cm² in phosphate-buffered solution (PBS) and 14.6 μA/mM cm² in artificial sweat. This sensitivity could be maintained under high tensile strain up to 100% without external structural design. The results presented here indicate the potential application of wearable smart textile towards non-invasive lactate monitoring.