Stretchable Electronic Platform for Soft and Smart Contact Lens Applications

Abstract

A stretchable platform with spherical-shaped electronics based on thermo- plastic polyurethane (TPU) is introduced for soft smart contact lenses. The low glass transition temperature of TPU, its relatively low hardness, and its proven biocompatibility (i.e., protection of exterior body wounds) fulfill the essential requirements for eye wearable devices. These requirements include optical transparency, conformal fitting, and flexibility comparable with soft contact lenses (e.g., hydrogel-based). Moreover, the viscoelastic nature of TPU allows planar structures to be thermoformed into spherical caps with a well-defined curvature (i.e., eye’s curvature at the cornea: 9 mm). Numerical modeling and experimental validation enable fine-tuning of the thermo - forming parameters and the optimization of strain-release patterns. Such tight control is proven necessary to achieve oxygen permeable, thin, nonde- velopable, and wrinkle-free contact lenses with integrated electronics (silicon die, radio-frequency antenna, and stretchable thin-film interconnections). This work paves the way toward fully autonomous smart contact lenses potentially for vision correction or sensing applications, among others

Untethered soft robotics

“…Thin and deterministic structures are not only applicable to stretchable and flexible circuits, but have also been used to transfer electronics onto non-developable (for example, spherical) surfaces 79 , including a contact lens with integrated microelectronics 80 ( Fig. 4d).…”

“…While ultimately constrained by the strain limit of the stiff internal materials, these circuits can interface well with existing devices, thereby enabling advanced sensing capabilities in soft circuits. Some work has taken steps towards untethered batteryfree circuitry by employing near-field communication (NFC) schemes to provide power and transmit data 74,80 NaTuRe elecTRoNics demonstrated untethered wearable devices by powering electronics and Bluetooth using lactate from human sweat 81 . Nanomaterials and conductive elastomer composites.…”

Microfluidic Contact Lenses

“…Moreover, to enhance the flowing biomarkers in the tear fluid mixing with fluorophores under dynamic nonequilibrium conditions, turbulence and nonturbulence mixers could be incorporated in the microfluidic contact lens design to improve the accuracy of real‐time measurement . With the development of emerging wearable technology, the microfluidic contact lens with stretchability and flexibility could also be fabricated by thermoplastic polymer …”

“…Over the last decade, electrochemical sensors were integrated in contact lenses to measure the concentration of glucose for diabetes management . Another contact lens sensor, Triggerfish (Sensimed), has received food and drug administration approval for measuring intraocular pressure for the clinical management of glaucoma . Bimetallic sensing‐resistive strain gauges were used as sensing materials to measure geometrical changes of corneoscleral junction correlated with intraocular pressure .…”

Contact Lens Technology: From Fundamentals to Applications

“…Cosmetic contact lenses, such as colored lenses and limbal‐ring lenses, are also popular, especially in Asian countries, and they are now classified as medical devices in the UK, US, China, Singapore, Malaysia, and Korea . Contact lenses were used as smart delivery systems to achieve extended drug releasing times, and as wearable biosensing platforms . On the other hand, contact lens wear was found to induce adverse effects, the most frequent being discomfort, microbial keratitis, allergies and corneal complications …”