Stretchable and Resilient Conductive Films on Polydimethylsiloxane from Reactive Polymer-Single-Walled Carbon Nanotube Complexes for Wearable Electronics

The increased consumer demand for flexible and wearable electronic devices has inspired researchers to explore new methods to fabricate low-cost, robust, and intrinsically stretchable conductive materials as alternatives to the standard rigid elements currently used in electronic devices. This work focuses on the inexpensive and rapid prototyping of stretchable electrodes based on the covalent grafting of single-walled carbon nanotubes (SWNTs) onto the surface of poly(dimethylsiloxane) (PDMS) elastomer substrates. SWNTs were dispersed in an organic solvent and functionalized through supramolecular association with an alkene-containing poly(phenylene ethynylene) (P2) polymer to yield stable dispersions of P2-SWNT complexes. Thin film electrodes were fabricated from P2-SWNT suspensions using a vacuum-assisted drop-casting method through a physical mask onto a porous membrane, followed by PDMS casting onto the patterned conductive thin films. The ability of the electrodes to conduct under strain was tested by monitoring the change in resistance for electrodes fabricated using different P2-SWNT loads per cm2. Electrodes with lower P2-SWNT loads, while having lower conductivity, presented stable conductive properties up to an applied strain of 100%. Additionally, the resilience of the P2-SWNT-PDMS electrodes was assessed using standard peel tests and strain-release cycles (0% to 100%) while monitoring the changes in resistance. This simple benchtop approach to fabricating stretchable electrodes via supramolecular functionalization of SWNTs and covalent grafting onto PDMS could enable the rapid prototyping of a wide range of devices, including strain sensors, flexible biosensors, and wearable electronic devices.