Fabrication of flexible electrode array based on PDMS for long-term in-vivo use

This paper proposes a novel flexible electrode array based on Poly(dimethylsiloxane). PDMS is widely used in biomedical applications but it has shortcomings such as high water absorption and generation of micro-cracks in metal patterns on PDMS. To overcome such shortcomings, we applied parylene-C as an intermediate layer between PDMS and metal on one hand, and also applied parylene-C to fill the porous PDMS surface in order to reduce water absorption into PDMS on the other hand. In addition, we adopted Pt as adhesion layer between Au and parylene-C deposited PDMS. To verify the suitability of Pt as an adhesion layer, we performed 10 × 10 grid adhesion tests and pull-off tests, and compared the adhesion strength of Pt with those of Ti and Cr that are commonly used as adhesion layers in MEMS processes. Lastly, to evaluate the electrical characteristics and water absorption property of the fabricated electrode, electrochemical impedance spectroscopy (EIS) was measured. We expect our electrodes provide high flexibility and low water absorption that is desired for long-term neural signal recording.