Toward High-Resolution Polymeric Neural Interfaces: A Practical Guide for Electron Beam Lithography.

Electron beam lithography (EBL) offers excellent opportunities to miniaturize and refine neurotechnological implants that serve important application domains such as the treatment of neurological conditions and interface the body with external machines. To improve the biocompatibility and signal resolution of the implantable part, miniaturization of the volume and scaling up the number of channels could enable improved long-term integration in tissue while at the same time extending the functionality. The standard is to pattern these devices using optical lithography, with a resolution limit at the microscale. In recent years, EBL has been employed to fabricate nanoscale electrical features on polymeric substrates. While plenty of data exist for EBL for standard material substrates such as silicon, challenges specific to polymeric substrates remain. These include charging of insulating materials, non-planarity, and heating of the substrate. This tutorial supports the understanding of thin-film micro- and nanofabrication process development for EBL to fabricate high-resolution neural implants. Furthermore, it serves as a guide for implementing EBL to achieve high-resolution structures, offering practical protocols for sub-micron features in polymer-based neuroprostheses, pushing this field closer to clinical implementation of these devices.