Hydrogel-based soft lenses integrate LED and RF antenna
Rather than relying on impermeable elastomeric polymers, the new device was based on a hydrogel-based material, opening the door to unique applications such as lenses with sensors and/or drug-delivery systems for the treatment of different eye disorders, at the congenital, post-surgery or trauma level. Such a wearable sensor-laden lens could perform continuous monitoring in an almost imperceptible manner.
About 130 million people worldwide wear contact lenses, mainly to correct their vision. Now, with electronic systems getting ever smaller and with the possibility of having electrical power on-lens, it becomes feasible to integrate a variety of transducers (i.e. physical, biochemical, etc.) into a lens. This is interesting for diagnosing and treating ocular diseases. The challenge is to integrate a complete autonomous system and make it as flexible as a soft lens, without compromising its oxygen-permeable nature and the integrity of the electronics components.
CMST, an imec research group at Ghent University, together with SEED Co., Ltd., demonstrated a semi-passive smart lens with blue LED light powered by an RF coupling. Besides power transfer, the RF link can be used to calibrate the integrated transducers and reading the sensors out into a handheld device for further post-processing.
The spherical‐shaped electronics were made by imec/CMST, whereas SEED Co., Ltd. was responsible for the seamless integration into the hydrogel-based soft lens.
The interconnect substrate is based on thermoplastic polyurethane (TPU), a material with a low glass transition temperature, relatively low hardness, proven biocompatibility, optical transparency, conformal fitting, oxygen permeability, 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). Very precise fine‐tuning of the thermoforming parameters and optimization of strain‐release patterns enabled to achieve oxygen permeable, thin, non-developable, and wrinkle‐free contact lenses with integrated electronics. Well-chosen gaps in the circuit provide for oxygen permeability of the lens.
Next, the researchers want to develop active lenses with extended power autonomy in order to drive and readout integrated transducers, then they’ll design a variety of micro-transducers compatible with such stretchable systems.
“With this technology, contact lens-type wearable devices could be mass produced as those existing contact lens products” noted Ms. Arai, researcher at SEED Co., Ltd., one of the developers of the device. “Moreover, the device could be installed on the outer side (tear film side), the inner side (cornea side), or in the center part of the contact lens. The adjustability of location is valuable for the biosensing field”. The R&D group is dedicating to the development of contact lens material for biological monitoring.
Imec – www.imec.be
SEED – www.seed.co.jp
Ghent University – www.UGent.be
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