Biofouling on protective coatings for implantable MEMS

Protective coatings can replace traditional packaging methods, which are often voluminous and may spoil the otherwise excellent opportunity for miniaturized implantable medical MEMS. The bio-growth on a selection of biocompatible protective coatings (TiO₂, DLC and Parylene) was investigated. The model system for evaluation was a diaphragm based acoustic resonator primary designed for fish identification. By detecting the shift in resonance frequency, we wanted to highlight the following; i) does the amount of biological growth vary for the different coatings? ii) if biofouling occurs, is the growth devastating for the device characteristics? We found that the resonance frequency did not change significantly. From this we conclude that the stiffness, represented by the spring constant for the resonating structure, was not affected. This result is of major importance also for other diaphragm based in vivo devices to be, e.g. pressure sensors, ultrasonic imaging devices, and dosage pumps.