Electrophoretic deposition of dielectric film on stimulation electrodes for the use in intraoperative neuromonitoring

Electrophoretic deposition (EPD) is a material processing technology which uses direct current (DC) voltage to deposit thin layers on a metallic substrate. EPD is a promising coating technology for medical devices due to its advantages such as thin homogenous layers and a broad range of usable substrates. The objective of this paper is to demonstrate how EPD can be deployed successfully to apply an insulation layer on a stimulation electrode. The Mapping suction probe by inomed Medizintechnik GmbH, Germany, was coated in this investigation. The unique feature of this product is that it combines both a surgical vacuum and a stimulation probe and is used for brain tumour resection. As for the insulation layer, ethylene chlorotrifluoroethylene (ECTFE) was chosen because of its good dielectric and biocompatible properties. ECTFE particles (Halar®6514, Solvay Specialty Polymer, Italy) were mixed with a solvent (Novec™ 7100DL Engineered Fluid, 3M™) to form a suspension. The coating process was partly automatized to ensure good repeatability and reproducibility. For coating, the stimulation probe was immersed in the suspension so that the counter electrode, a stainless-steel net, surrounded it equidistantly. A heat treatment of the coated device in an oven (FED56, Binder, Germany) was required afterwards to melt the deposited polymer particles. After the heat treatment, a glossy black layer (layer thickness 42 μm) was observed on the substrate. A smooth and homogenous surface confirmed that the coating is suitable for surgical application. However, due to a high evaporation rate of the solvent, the ratio of particles and solvent changes and the coating process will have to be controlled in the future to achieve a stable process. Further advantages of EPD such as short processing time, straightforward process flow and scalability enables high production quantities which is attractive for industrial application. EPD might be a promising coating technology for medical devices in the future