Biodegradable, inkjet-printed neural interface

Abstract

The evolution of the neural prosthesis as a clinical solution holds significant promise for treatment and management of neurological disorders such as Parkinson’s, Alzheimer’s and Epilepsy. In this work, we developed and built a new generation of biodegradable and flexible neural interfaces that have the potential to record high-fidelity electrical activity from the brain for monitoring neurological diseases and guiding therapeutic decisions without the need for prosthetic device resection. For that purpose, we utilized innovations in inkjet printing technology aimed at overcoming limitations of current semiconductor fabrication techniques on low melting point polymer substrates. Inkjet printing allows for the fabrication of electronic devices at a resolution of a few tens of microns with reduced material waste, low cost and low temperatures. The devices in this study were fabricated on flexible polymers that allow for reduced mechanical mismatch between soft brain tissue and implanted devices improving the biocompatibility of prosthetic intervention. The devices were fabricated on polycaprolactone (PCL), a biodegradable polyester with a low melting point of around 60 °C and polyimide (PI) a low moisture uptake and biocompatible polymer. Electrodes for neural recording were built at 50 μm diameter using (3,4- ethylenedioxytiophene)-poly(styrenesulfonate) (PEDOT:PSS). The latter is a low impedance organic semiconductor and it was deposited in 10 layers via non-contact inkjet printing reducing the impedance to ∼200 Ω at 1 KHz leading to increased electrical and ionic conductivities. In-vitro validation was performed on both rat PC12 cells and isolated neural rat retina to confirm their biocompatibility of the fabricated devices and their ability to record single unit activity from spontaneously firing neurons. The study shows the potential of inkjet printing for building high performance, biodegradable and flexible neural interfaces.