Hydrogel-based bimodal sensors for high-sensitivity independent detection of temperature and strain

Avoiding crosstalk between strain and temperature detection is crucial for bimodal hydrogel sensors, yet achieving high sensitivity for both parameters while maintaining signal decoupling remains a significant challenge. In this study, a bimodal sensor was developed by locally coating poly (3,4-ethylene dioxythiophene): polystyrene sulfonate (PEDOT: PSS) onto the hydrogel surface, creating distinct regions for strain and temperature detection. These regions form localized strain concentration zones and wrinkle structures, respectively. The localized strain concentration enhances the sensor's sensitivity from 8.5 to 18.5. Additionally, the sensor demonstrates a low detection limit (0.2 %), a wide detection range (up to 1356 %), a fast response time, and excellent cyclic stability for strain measurements. The temperature detection region, leveraging the thermoelectric effect, improves the Seebeck coefficient of the PEDOT: PSS coating from 20 to 122.86 μVK^-1 through de-doping and energy band modulation. Moreover, the temperature sensing of the PEDOT: PSS coating features good cyclic stability, a rapid response time, and versatile testing capabilities. This innovative structural design effectively decouples strain and temperature signals across a broad strain range (0-600 %). These sensors hold potential applications in human health monitoring and as electronic skin for flexible robotics.