gms | German Medical Science

Objective: Modern implants often use flexible polymer substrates to enhance biocompatibility. Retinal implants also utilize these polymers like polyimide or parylene, but they can release volatile organic compounds (VOCs) when treated with high temperatures, limiting their use in high-purity cleanrooms. To address this, we use silicon ultrathinning. The goal of this study is to evaluate whether ultrathinning is sufficient for flexible retinal implants to conform to the eye's anatomy and reduces immune responses.

Materials and Methods: An FEM simulation will assess the mechanical properties of ultrathin silicon, modeling both the MEA and ASIC within a 3D stack. The goal is to evaluate the flexibility, yield strength, and stiffness of the implant across wafer thicknesses (30–70 µm), focusing on its ability to adapt to the eye’s concave shape. Wafers will also be thinned to the same range, cut into MEA dummies, and tested for mechanical flexibility. Those mechanical tests will be compared to simulation Results. Silicon dies will be implanted into cow eyes, fixed with PFA, and sectioned for microscopic analysis of implant behavior.

Results: Building on our previous work, more FEM simulations are being conducted to further refine the evaluation of ultrathin silicon's mechanical properties. However, simulations are expected to offer valuable insights into ultrathin silicon's flexibility. Implantation tests will evaluate whether the silicon dies conform to the eye’s concave shape for safe placement. These tests will also provide information on injury risk and mechanical adaptability.

Discussion: This study investigates whether retinal implants can be fabricated by ultrathinning without damaging the eye. Silicon ultrathinning may not provide enough flexibility for optimal conformity to the eye’s concave shape. However, if successful, functional MEAs and ASICs could be developed.

Acknowledgment: This work was supported by the German Research Foundation grant 424556709.