Stretchable and Resilient Conductive Films on Polydimethylsiloxane\nfrom Reactive Polymer-Single-Walled Carbon Nanotube Complexes for\nWearable Electronics

Abstract

The increased consumer\ndemand for flexible and wearable electronic\ndevices has inspired researchers to explore new methods to fabricate\nlow-cost, robust, and intrinsically stretchable conductive materials\nas alternatives to the standard rigid elements currently used in electronic\ndevices. This work focuses on the inexpensive and rapid prototyping\nof stretchable electrodes based on the covalent grafting of single-walled\ncarbon nanotubes (SWNTs) onto the surface of poly­(dimethylsiloxane)\n(PDMS) elastomer substrates. SWNTs were dispersed in an organic solvent\nand functionalized through supramolecular association with an alkene-containing\npoly­(phenylene ethynylene) (<b>P2</b>) polymer to yield stable\ndispersions of <b>P2</b>-SWNT complexes. Thin film electrodes\nwere fabricated from <b>P2</b>-SWNT suspensions using a vacuum-assisted\ndrop-casting method through a physical mask onto a porous membrane,\nfollowed by PDMS casting onto the patterned conductive thin films.\nThe ability of the electrodes to conduct under strain was tested by\nmonitoring the change in resistance for electrodes fabricated using\ndifferent <b>P2</b>-SWNT loads per cm². Electrodes\nwith lower <b>P2</b>-SWNT loads, while having lower conductivity,\npresented stable conductive properties up to an applied strain of\n100%. Additionally, the resilience of the <b>P2</b>-SWNT-PDMS\nelectrodes was assessed using standard peel tests and strain-release\ncycles (0% to 100%) while monitoring the changes in resistance. This\nsimple benchtop approach to fabricating stretchable electrodes via\nsupramolecular functionalization of SWNTs and covalent grafting onto\nPDMS could enable the rapid prototyping of a wide range of devices,\nincluding strain sensors, flexible biosensors, and wearable electronic\ndevices.