Nanocomposite Hydrogels with Temperature Response for Capacitive Energy Storage

Functional hydrogels are three-dimensional polymeric networks with potential applicability in the field of wearable electronics. However, hydrogels are often used to develop devices with only one functionality. In this work, a multifunctional hydrogel consisting of poly(3,4-ethylenedioxythiophene) (PEDOT), alginate (Alg), carbon nanoparticles (CNPs), and manganese oxide has been manufactured for devices that can simultaneously store energy (supercapacitor) and sense temperature. The Alg and PEDOT interpenetration allows for obtaining a flexible and electrically conductive hydrogel with an open and interconnected porous structure. The incorporation of CNPs improves electrical conductivity and confers synergies with manganese oxide, which provide energy storage capability. Furthermore, the resistance of the hydrogel varies linearly with the temperature, this behavior being observed consistently and without hysteresis throughout consecutive heating and cooling cycles. Thus, the PEDOT/Alg/CNP/MnO₂ hydrogel shows good capacitance (42 mF cm^–2), capacitance retention (87%), and good temperature sensitivity (−1.05% °C^–1).