Polarity-switchable ionic diode

The unidirectional current conduction of diodes is fundamental to integrated circuits. Current rectifying diodes (electronic and ionic) rely on permanently establishing heterojunctions by using two opposite materials, making it infeasible to modulate the rectification polarity. We report a polarity-switchable ionic diode based on a single material of mixed-ion polyelectrolyte hydrogel. By applying a programming electric field, asymmetric ion distribution is induced within the homogeneous gel. This generates a potential barrier that enables current rectification. The programming process is reversible, allowing on-demand reconfiguration of the rectification polarity. At a circuit level, this introduces reconfigurability not achievable with current diodes. Our work establishes a new platform for designing next-generation neuromorphic devices with versatility far beyond current devices.