Bipolar electrochemistry-driven wireless drug loading and energy harvesting in conductive hybrid hydrogels

Bipolar electrochemistry enables wireless and spatially controlled redox reactions on (semi)conductive objects immersed in an electrolyte. Here, we investigate advanced bipolar electrochemistry applications using flexible bipolar electrodes coated with hybrid films of conductive polymer poly(3,4-ethylenedioxythiophene) and alginate hydrogels. These coatings allow for the wireless creation of reversible redox and chemical gradients, providing targeted drug loading and energy harvesting opportunities. We use cyclic voltammetry, electrochemical impedance spectroscopy, Raman microscopy, and X-ray photoelectron spectroscopy to characterize distinct redox regions within the bipolar electrode. The wireless and selective loading of a model drug, fluorescein, into the hydrogel, demonstrated control over drug distribution, suggesting an alternative to conventional uniform doping techniques. Furthermore, cutting the gradient-encoded bipolar electrode and closing an external circuit between the halves, enables energy recovery through a concentration cell mechanism. Our findings illustrate the potential of bipolar electrochemistry in creating versatile platforms that bridge materials science, electrochemistry, and bioelectronics for innovative biomedical and energy applications.