De Smet, Herbert

Vanfleteren, Jan

Vasquez Quintero, Andrés Felipe

Verplancke, Rik

English

Ghent University Academic Bibliography

Stretchable platform enabled with wireless power for smart contact lenses  Andrés Vásquez Quintero, Rik Verplancke, Jelle De Smet, Herbert De Smet and Jan Vanfleteren Center for Microsystems Technology (CMST) imec and Ghent University Technologiepark 915, B-9052 Ghent Belgium  A smart contact lens, envisioned to correct or improve the vision, entails the integration of electronics components such as: Si chips, power source, electro-optic module and Radio Frequency (RF) antenna. The latter is thought to be the main interface for wireless communication and energy transfer at the High Frequency (HF) range. These components are interconnected by non-conventional electrical layouts in a fully stretchable platform which fulfill the essential requirements for eye wearable devices (conformal fitting and optical transparency, etc.). The fabrication process presented here relies on the thermoforming of a flat platform (electronics layout, chips and RF antenna) into a curvilinear spherical geometry fitting the eye’s shape (curvature radius: 9 mm). In particular, we introduce the platform’s mechanical carrier as a soft and biocompatible thermoplastic polyurethane (TPU), which serves as the thermoforming element and provides the essential support and stretchability. A developed thermoforming 3D and time domain Finite Element Model (FEM) using COMSOL is used for the prediction of the final lens curvature and the analysis of the induced mechanical stress throughout the thermoforming steps. The electronic platform includes a thinned-down (25 μm) Near-Field Communication (NFC) chip (M24RL64E from ST) which incorporates an RF energy harvesting module providing a direct current output when coupled magnetically. The NFC chip is interfaced with an ultra-compact RF loop antenna. The antenna was designed and optimized with a combination of analytical equations and subsequent RF momentum simulations with the software Advanced Design Systems. This optimization and a modified pattern plating process resulted in a width, gap, loops and thickness of the antenna of: 24 μm, 6 μm 13 and 10 μm, respectively, which in turn provided a quality factor around 10. Two port S parameters, reading distances, power transfer and frequency matching were validated by comparing fabricated prototypes and RF momentum models, enabling HF energy transfer for smart contact lenses and even other wearable devices in close contact with the body. A measured inductance of 4.78 μH combined with the NFC chip input capacitive impedance (27 pF) were able to communicate with an NFC-ready smartphone and custom reader at 13.56 MHz in order to give external power to an on-lens micro solid-state light emitting diode. The mechanical FEM model served to optimized meandered designs on the TPU-based platform in order to accommodate mechanical deformation during thermoforming, which in turn allowed for an optimal wrinkle-free RF antenna design and platform design. Parallel processing in combination with a short thermoforming step at relatively low temperature, paves the way towards mass scalable fabrication of soft smart contact lenses with integrated electronic components, including Si chips, electro-optics, RFID antennas, micro-size batteries and photovoltaic cells, among others.  Character count: 2994/3000 

Stretchable platform enabled with wireless power for smart contact lenses

https://biblio.ugent.be/publication/8542751/file/8543211

Stretchable platform enabled with wireless power for smart contact lenses

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Ghent University Academic Bibliography