Printable and transparent micro-electrocorticography (μECoG) for optogenetic applications

Micro-electrocorticography (μECoG) displays advantages over traditional invasive methods. The μECoG electrode can record neural activity with high spatial-temporal resolution and it can reduce implantation side effects (e.g. vascular and local-neuronal damage, tissue encapsulation, infection). In this study, we propose a printable transparent μECoG electrode for optogenetic applications by using ultrasonic microfluid printing technique. The device is based on poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) as a conductive polymer, polydimethylsiloxane (PDMS) as an insulating polymer and poly(chloro-para-xylylene) (Parylene-C) as the device substrate. We focus on ultrasonic microfluid printing due to its low production cost, excellent material handling capability, and its customizable film thickness (down to 5-20 microns). The ultrasonic fluid-printed μECoG displays high spatial resolution and records simulated signal (0-200 Hz sine wave) effectively with low electrode impedance (50-200 kOhms@1kHz). The μECoG also shows good biocompatibility suitable for customizable chronic implants. This new neural interfacing device could be combined with optogenetics and Brain-Computer Interface (BCI) applications for a possible future use in neurological disease diagnosis and rehabilitations.