Self-Lubricating, Living Contact Lenses

The increasing prevalence of dry eye syndrome in aging and digital societies compromises long-term contact lens (CL) wear and forces users to regular eye drop instillation to alleviate discomfort. Here a novel approach with the potential to improve and extend the lubrication properties of CLs is presented. This is achieved by embedding lubricant-secreting biofactories within the CL material. The self-replenishable reservoirs autonomously produce and release hyaluronic acid (HA), a natural lubrication and wetting agent, long term. The hydrogel matrix regulates the growth of the biofactories and the HA production, and allows the diffusion of nutrients and HA for at least 3 weeks. The continuous release of HA sustainably reduces the friction coefficient of the CL surface. A self-lubricating CL prototype is presented, where the functional biofactories are contained in a functional ring at the lens periphery, outside of the vision area. The device is cytocompatible and fulfils physicochemical requirements of commercial CLs. The fabrication process is compatible with current manufacturing processes of CLs for vision correction. It is envisioned that the durable-by-design approach in living CL could enable long-term wear comfort for CL users and minimize the need for lubricating eye drops.

Power Scavenging Microsystem for Smart Contact Lenses

On-the-eye microsystems such as smart contacts for vision correction, health monitoring, drug delivery, and displaying information represent a new emerging class of low-profile (≤ 1 mm) wireless microsystems that conform to the curvature of the eyeball surface. The implementation of suitable low-profile power sources for eye-based microsystems on curved substrates is a major technical challenge addressed in this paper. The fabrication and characterization of a hybrid energy generation unit composed of a flexible silicon solar cell and eye-blinking activated Mg-O2 metal-air harvester capable of sustainably supplying electrical power to smart ocular devices are reported. The encapsulated photovoltaic device provides a DC output with a power density of 42.4 µW cm-2 and 2.5 mW cm-2 under indoor and outdoor lighting conditions, respectively. The eye-blinking activated Mg-air harvester delivers pulsed power output with a maximum power density of 1.3 mW cm-2 . A power management circuit with an integrated 11 mF supercapacitor is used to convert the harvesters' pulsed voltages to DC, boost up the voltages, and continuously deliver ≈150 µW at a stable 3.3 V DC output. Uniquely, in contrast to wireless power transfer, the power pack continuously generates electric power and does not require any type of external accessories for operation.

Smart Contact Lenses-A Step towards Non-Invasive Continuous Eye Health Monitoring

According to the age-old adage, while eyes are often considered the gateway to the soul, they might also provide insights into a more pragmatic aspect of our health: blood sugar levels. This potential breakthrough could be realized through the development of smart contact lenses (SCLs). Although contact lenses were first developed for eyesight correction, new uses have recently become available. In the near future, it might be possible to monitor a variety of ocular and systemic disorders using contact lens sensors. Within the realm of glaucoma, SCLs present a novel prospect, offering a potentially superior avenue compared to traditional management techniques. These lenses introduce the possibility of non-invasive and continuous monitoring of intraocular pressure (IOP) while also enabling the personalized administration of medication as and when needed. This convergence holds great promise for advancing glaucoma care. In this review, recent developments in SCLs, including their potential applications, such as IOP and glucose monitoring, are briefly discussed.

A Microfluidic Contact Lens to Address Contact Lens-Induced Dry Eye

The contact lens (CL) industry has made great strides in improving CL-wearing experiences. However, a large amount of CL wearers continue to experience ocular dryness, known as contact lens-induced dry eye (CLIDE), stemming from the reduction in tear volume, tear film instability, increased tear osmolarity followed by inflammation and resulting in ocular discomfort and visual disturbances. In this article, to address tear film thinning between the CL and the ocular surface, the concept of using a CL with microchannels to deliver the tears from the pre-lens tear film (PrLTF) to the post-lens ocular surface using in vitro eye-blink motion is investigated. This study reports an eye-blink mimicking system with microfluidic poly(2-hydroxyethyl methacrylate) (poly(HEMA)) hydrogel with integrated microchannels to demonstrate eye-blink assisted flow through microchannels. This in vitro experimental study provides a proof-of-concept result that tear transport from PrLTF to post-lens tear film can be enhanced by an artificial eyelid motion in a pressure range of 0.1-5 kPa (similar to human eyelid pressure) through poly(HEMA) microchannels. Simulation is conducted to support the hypothesis. This work demonstrates the feasibility of developing microfluidic CLs with the potential to help prevent or minimize CLIDE and discomfort by the enhanced transport of pre-lens tears to the post-lens ocular surface.

Tear-Based Aqueous Batteries for Smart Contact Lenses Enabled by Prussian Blue Analogue Nanocomposites

Batteries for contact lenses fabricated by conventional methods could cause severe damage to the eyes if broken. Herein, we present flexible aqueous batteries that operate in tears and provide a safe power supply to smart contact lenses. Nanocomposite flexible electrodes of carbon nanotubes and Prussian blue analogue nanoparticles for cathode and anode were embedded in UV-polymerized hydrogel as not only a soft contact lens but also an ion-permeable separator. The battery exhibited a discharging capacity of 155 μAh in an aqueous electrolyte of 0.15 M Na-ions and 0.02 M K-ions, equivalent to the ionic concentration of tears. The power supply was enough to operate a low-power static random-access memory. In addition, we verified the mechanical stability, biocompatibility and compatibility with a contact lens cleaning solution. It could ultimately enable a safe power supply for smart contact lenses without risk of injury due to the leakage or breakage of the battery.

Recent Progress in Wireless Sensors for Wearable Electronics

The development of wearable electronics has emphasized user-comfort, convenience, security, and improved medical functionality. Several previous research studies transformed various types of sensors into a wearable form to more closely monitor body signals and enable real-time, continuous sensing. In order to realize these wearable sensing platforms, it is essential to integrate wireless power supplies and data communication systems with the wearable sensors. This review article discusses recent progress in wireless technologies and various types of wearable sensors. Also, state-of-the-art research related to the application of wearable sensor systems with wireless functionality is discussed, including electronic skin, smart contact lenses, neural interfaces, and retinal prostheses. Current challenges and prospects of wireless sensor systems are discussed.