Fabrication and evaluation of the PDMS-based soft micro electrode for the retinal prosthesis

In the past decades, many types of micro electrodes have been reported for the measurement of biological signals or for the stimulation to the retinal prosthesis, and most of these electrodes are fabricated on the surface of hard or flexible substrates such as silicon, polyimide and parylene. In spite of many advantages of these substrates, they have some limits to be implanted inside the sensitive body (e.g.: eye or brain) owing to the movement artifact or the damage to the tissue. Recently, the PDMS which is soft, elastic, biocompatible and has good water and gas permeability has attracted great attentions as a tissue like substrate. However, the PDMS has many defects as a substrates such as inferior adhesiveness of metal layer or poorer resistances to the developing chemicals. In this paper, a polydimethylsiloxane (PDMS)-based flexible and implantable micro electrode was fabricated for the retinal prosthesis. The patterning of the electrodes and the wires was performed through the photolithography and chemical etching process after e-beam deposition Ti and Au, and the thick electrodes (30mum) were fabricated through the electroplating process. We carried out in-vivo test for the evaluation of biocompatibility by implanting electrodes under the ICR mouse skin for 45 days. The electrode was implanted under the retina of rabbit's eye to investigate the feasibility as a retinal prosthesis