High capacitance freestanding PEDOT:PSS electrodes for low-frequency electric field delivery

Since the 18th century, the use of electrical stimulation has been widely used to treat disease and control the development of cells, tissues, and organ growth. Electric fields and currents are used to mimic endogenous signals that regulate cell behavior to both better understand their mechanism of action and provide control for bio-engineering and therapeutics. While delivery of electric fields has proven useful, low frequency field delivery remains inaccessible with standard metal electrodes. This delivery of low frequency electric fields is limited by areal capacitance, resulting in low charge injection capacities or Faradaic reactions, which can generate cytotoxic by-products. Here, we demonstrate freestanding poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) electrodes, which conduct both ions and electrons, resulting in electrode capacitance that scales with volume rather than area. We show that these electrodes can be used to generate electric fields in an aqueous medium at frequencies as low as 0.1 Hz. Specifically, we demonstrate persistent electric fields in aqueous media without exceeding the electrochemical window of water, previously unattainable using standard electrodes. Finally, we show that thick PEDOT:PSS electrodes are not cytotoxic. This work opens the path toward delivery of low frequency stimulating electric fields to cells and tissues both in vitro and in vivo.