Near-Field Communication Powered Hydrogel-Based Smart Contact Lens

Nowadays, smart contact lenses (SCLs) display interesting features for healthcare monitoring; however, their comfort and practical usability strongly depend on the outermost material in contact with the eye. In this publication, the embedding of a custom-made and thermoformed Near-Field Communication based circuit in a conventional soft CL is presented. The circuit is composed of gold tracks on polyimide between thermoplastic polyurethane layers (insert), while the lens is based on industry standard double-molding process of poly(2-hydroxyethyl methacrylate) with proven compatibility with corneal tissue. The lens shows stable geometrical parameters (bevel landing area) thus enabling a practical implementation. Finite element method models are used to optimize the thermoforming process in order to provide a stable and desired curvature of the insert before the embedding process. While the insert is designed to allow oxygen transmission at the center of the lens, a custom-made ultra-compact radio-frequency antenna provides communication and wireless power transfer both in air and inside saline solutions. The successful combination of the intrinsic soft mechanical properties of the wirelessly powered electronic insert with conventional hydrogel materials and manufacturing processes delivers a practical solution for SCLs. This enables non-invasive applications in fields such as vision correction and/or biomedical sensing.