DFG: Transduction of smart hydrogel swelling state by advanced flexible CNT-based MEMS capacitors on a membrane platform (HydroMEMS)

Smart hydrogels are biocompatible 3D polymer networks that change volume in response to stimuli such as temperature, humidity, organic vapors, or biomolecules—making them highly attractive for biomedical and chemical sensing. Yet their potential is often underused because reliable, robust ways to transduce hydrogel swelling into an electrical signal are still limited. This project develops a miniaturizable, energy-efficient sensor concept based on electromechanical transduction. It uses self-forming flexible microstructures made from vertically aligned carbon nanotube (VACNT) pillar electrodes. When the hydrogel swells, it deforms these pillars, measurably changing their resistive–capacitive properties. We will combine simulations and extensive experiments to uncover the underlying physics linking hydrogel swelling, force distribution, and electrical readout. Different hydrogel/transducer configurations will be explored to achieve both linear and switch-like sensor behavior. As a first demonstrator, we target detection of volatile organic compounds in gases, while also validating the platform’s versatility across multiple hydrogel types and environments (gas and liquid) and establishing robust closed-loop operating regimes.