Self‐Moisturizing Smart Contact Lens Employing Electroosmosis

Abstract

dry eye syndrome, it is important to keep the lens moist and maintain tears between the CL and the ocular surface, which is here referred to TCO (the initial letters of tear, contact lens, and ocular). Conventional rehydration by regular eye drops, the electrical stimulation of the lacrimal gland, [17] and treatment with a punctum plug [18] will increase the total tear fluid in eye, but cannot directly address the maintenance of the amount of TCO. The only example so far of a smart CL for maintaining the TCO is that of Lee et al., who developed a CL coated with single layer of graphene which decreases the moisture evaporation. [19] Hence, there is still a high demand to develop a CL equipped with an antidehydration function.In this paper, we report that electroosmotic flow (EOF) can be induced in a soft CL in order to maintain the moisture of the lens. EOF is the motion of water induced by an applied voltage across a fluid conduit like a capillary tube [20,21] or a porous material such as hydrogels. [22,23] When the fluid conduit contains fixed electrical charges, the dominant electromigration of the mobile counterions produces net water flow. [24,25] For example, due to the large amount of carboxyl groups in keratin in the stratum corneum of the skin, the transdermal iontophoretic current is known to be accompanied by the EOF from anode to cathode, which assists the penetration of drugs into the skin. [26][27][28] Here, we first developed charge-fixed hydrogel materials and studied their properties as the fluid conduit for EOF generation. The density of the fixed charge was optimized by adjusting the mechanical strength and the efficiency of EOF generation (EOF strength). It was successfully demonstrated that the upward EOF within the soft CL can maintain moisture of the lens itself and also the TCO as illustrated in Figure 1, by in situ monitoring of conductance and by microscope observations. As an example of a built-in power source for EOF generation, the mounting of batteries (Mg/O 2 battery and fructose/O 2 enzymatic battery) was also demonstrated. Results and Discussion EOF Generation in Charged HydrogelsThe hydrogel materials composed of 2-hydroxyethyl methacrylate (HEMA), methyl methacrylate (MMA), and methacrylic acid (MA) were prepared using a the copolymerization ratio of Contact lenses (CLs) can be a cause of "dry eye syndrome" that can lead to corneal wounds and inflammation as well as a feeling of discomfort. To prevent the dry eye, it is important to keep the lens moist and maintain tears between the CL and the ocular surface. Here, the use of electroosmotic flow (EOF) in a CL is reported as a novel mechanism for antidehydration. A CL made from a charged hydrogel has served as the fluid conduit for EOF generation. The charge density of the gel is optimized by varying the composition ratio of anionic monomer having carboxyl group, by taking into account the efficiency of EOF generation and the mechanical strength of the hydrogels. By in situ monitoring of conductance and by microscope observations,...

Transdermal electroosmotic flow generated by a porous microneedle array patch

“…McIlvaine buffer (pH 7.0) (Supplementary Table 2 ) was used as the electrolyte solution. Ag/AgCl (AgCl + e → Ag + Cl − ) and Ag (Ag → Ag + + e) were used for a cathode and an anode, respectively 54 . Therefore, no bubbles were observed from the electrodes during the current application.…”

“…Electroosmotic flow (EOF) through PMN modified with charged hydrogel. By using the side-by-side Franz cell 6,54 shown in Fig. 3a, the efficiency of EOF generation (EOF strength) was evaluated to study the effect of the modification of poly-2-acrylamido-2-methylpropane sulfonate (PAMPS) into the porous structures of PMN.…”

Prospects for Additive Manufacturing in Contact Lens Devices

“…A smartphone was used as a reader to record the diffracted light signals coming out of the smart CL, which were correlated with the glucose concentrations. [ 111 ] Smart CLs can help to correct the color blindness. A rhodamine derivative was incorporated in commercial CLs to filter out specific wavelength bands (545–575 nm) to correct color vision blindness.…”

“…Reproduced with permission. [ 111 ] Copyright 2019, Wiley. F) Photographs of contact lens integrated with electrochromic alarm system above forefinger, and artificial eye.…”

“…Photonic CLs can be utilized for continuous glucose monitoring wirelessly with the smartphones used as readers. [ 111 ] This reported lens had photonic microstructures imprinted on its surface and the change in glucose concentrations led to the modification of their geometry. This led to the change in the optical reflection properties of the microstructures, which can be detected via a smartphone.…”