Fabrication of thin-film electrodes and organic electrochemical transistors for neural implants

Bioelectronic medicine, which involves the delivery of electrical stimulation via implantable electrodes, is poised to advance the treatment of neurological conditions. However, current hand-made devices are bulky, invasive and lack specificity. Thin-film neurotechnology devices can overcome these disadvantages. With a typical thickness in the range of micrometers, thin-film devices demonstrate high conformability, stretchability, are minimally invasive and can be fabricated using traditional lithography techniques. Despite their potential, variability and unreliability in fabrication processes hinder their wider utilization. Here, we detail a fabrication method for thin-film poly(ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) electrodes and organic electrochemical transistors. The use of organic materials makes these devices particularly well suited for bioelectronic medicine applications as they show superior mechanical and electrical matching of biological tissues compared with devices made of inorganic materials. The procedure details the entire process, including mask design, the fabrication through three photolithography stages, the integration with larger-scale electronics, implantation procedures and the expected electrical characterization metrics. The nanofabrication protocol requires at least 3 d and is suitable for those familiar with lithographic fabrication procedures. The surgery requires up to 10 h and is suitable for those familiar with in vivo implantation procedures.