Molecularly hybridized ionically conductive hydrogels prepared by thiol-ene click crosslinking for flexible mechanosensors

Conductive hydrogels with integrated high mechanical robustness and conductivity are increasingly explored in flexible electronic devices. Herein, ionically conductive hydrogels are designed by molecularly hybridizing hydrophilic polymers and hydrophobic polymers into one network. Formation of polymer network occurs among double bond end-capped polyethylene glycol (A-PEG-A), double bond end-capped polydimethylsiloxane (A-PDMS-A) and pentaerythritol tetra(3-mercaptopropionate) (PETMP) via an efficient thiol-ene click crosslinking process. PDMS helps to improve the mechanical properties of hydrogels and KCl is introduced as a conductive component. Compared with pure PEG hydrogel, the stretchability and tensile strength of molecularly hybridized conductive hydrogels (PEG-PDMS/K+ hydrogels) are increased by 9 times and 27 times, respectively. Utilizing PEG-PDMS/K+ hydrogels as key signal-converting materials, flexible mechanosensors, including resistive strain sensors, piezoresistive pressure sensors and capacitive pressure sensors, are fabricated and further demonstrated in monitoring various strains and pressures generated during joint bending, finger pressing, handwriting, water droplets dripping, etc. Overall, the molecularly hybridized conductive hydrogels are expected to provide a versatile molecular approach to functional hydrogels for future soft devices.