Encapsulation Material for Retinal Prosthesis With Photodetectors or Photovoltaics

Retinal prosthesis is one of the key strategies for tackling retinitis pigmentosa – a group of genetic disorders that can cause blindness. However, further advancement of retinal implant is hindered by some technical limitations. Current state-of-the-art retinal implants failed within two-three years after implant and showed a significant decrement in their visual acuity. The purpose of this investigation is to search for a material that is better suited for the packaging of retinal implants. Specifically, the study was conducted under the assumption that image acquisition is done internally, i.e. without the use of an external camera. Polydimethylsiloxane (PDMS) and polyimide (PI) are some of the most commonly used materials in implantable devices. In addition, colorless transparent polyimide (CPI) was studied to overcome the optical limitations of PI. Finally, liquid crystal polymer (LCP) and cyclic olefin copolymer (COC) were added in the comparison due to their promising results regarding their expected longevity. In this experiment, PDMS, CPI, and COC outperformed the other materials in optical transparency. Considering the excellent encapsulation properties due to thermoplasticity while being able to be fabricated into a micro-lens array, we believe COC is worth further in-depth investigation for further advancement in the field of a retinal prosthesis.