Implantable Glass Waveguides and Coating Materials for Chronic Optical Medical Applications

An innovative fabrication process of glass waveguides on silicon substrates for miniaturized implants is presented. Thin glass was bonded on oxidized silicon wafers and patterned using wet etching. Multimode waveguides with different shapes and a low surface roughness as well as low scattering of light were successfully fabricated. For efficient coupling of light and accurate alignment, KOH-grooves were etched in the silicon with respect to the glass waveguides to attach optical fibers from external light sources. Towards higher biostability, several coating materials were evaluated in accelerated in vitro tests in 60°C PBS for the first time over a long period of time regarding their optical properties. Ti0
₂
, SiC, polyimide, Parylene C and SU-8 showed a very stable optical transmittance after 320 days in accelerated aging while PECVDSi
₃
N
₄
showed significant changes within the first days.