Monitoring Water Permeation in Flexible Bioelectronic Devices

Most bioelectronic interfaces call for long-term operation. Their formfactor requires new packaging strategies to ensure hermeticity, thinness and mechanical compliance. Inspired from display technologies, organic-inorganic multilayers are promising candidates to package thin, flexible and miniaturised bioelectronic devices. Besides the materials challenges associated with the choice of suitable thin films, stacking and deposition methods, quantitative evaluation of their barrier performance is a must. We have developed real-time monitoring methods of permeability or water transmission rate of thin film multilayers leveraging magnesium (Mg) degradation under physiological conditions. Water permeation drives Mg hydrolysis. Using Mg film electrical and electrochemical sensors prepared with thin-film microfabrication, embedded in bioelectronic interfaces, ultra-low detection of water permeation (as low as of 3.3 × 10^-8 g/m²/day at room temperature) can be achieved. This method should provide useful information on novel encapsulation strategies for miniaturised, long-term bioelectronic implantable systems.