Design and Implementation of an Inline Coater for Solvent-Based Polyurethane Microelectrode Insulation

Abstract The growing use of microelectrodes in medical technology requires scalable manufacturing processes for high-quality, reproducible, and biocompatible insulation layers. This need is particularly evident in advanced neuroprosthetic systems for upper-limb amputees, where reliable neural and muscular interfaces are essential for intuitive control of bionic prostheses. Current developments aim to integrate electrode-equipped, osseointegrated implants capable of bidirectional communication with the neuromuscular system. Conventional batch coating techniques for microelectrodes often struggle to achieve consistent coating properties at industrial scale. In this work, we present the design and implementation of an inline coater for the continuous deposition of solvent-based polyurethane layers on fine metallic wires. The automated system enables controlled withdrawal of wires from a polymer solution, providing precise adjustment of coating thickness through key process parameters such as solution composition and withdrawal speed. First coating trials on microwires demonstrated homogeneous polyurethane insulation layers. Confocal laser scanning microscopy confirmed that the resulting film thickness correlates predictably with the selected process parameters, highlighting the potential of this approach for scalable production of durable and biocompatible wire insulation for medical applications.