Laser-Induced Surface Modification of Contact Lenses

The authors report on the laser-induced modification of surface properties of contact lenses. Selective areas of the surface of commercial silicon-hydrogel contact lenses are patterned in array formats using different powers of the CO₂ laser. 1D arrays of different groove densities, channels, and 2D intersecting architecture are fabricated. Contact angle measurements are carried out to measure the surface hydrophilicity, and extent of hydration is linked with the surface profile properties and the space gap between the fabricated patterns, which are controlled by the beam exposure time, beam power, and scan speed. Laser treatment of contact lenses results in improved hydration proportional to the density of laser ablated segments on the surface. The hydration time of water droplets on different lens surfaces is also recorded – all 2D patterned lenses show faster hydration as water quickly diffused into the bulk of the lens due to the extended interfacial area between the contact lens and the water droplet as a consequence of larger areal modification in 2D as compared with 1D patterns. The best wettability properties are obtained with 0.3 mm space gap, 9 W power, and 200 mm s⁻¹ scan speed. Optical microscopy is used to image the 3D surface profiles of the modified lenses and the depth of the patterns and is correlated with the experimental observations. The maximum depth of 40 µm is observed with 0.3 mm space gap, 9 W, and 200 mm s⁻¹ scan speed. Optical transmittance of broadband white light is measured to assess the surface treatment effects on the contact lenses. A large exposure and dense patterning of contact lens result in decreased (down to a minimum of 45%) in the light transmittance, which dictates the practical usability of such patterning. Surface treatment of contact lenses can be utilized to deposit stable conducting connection for on-lens-LEDs, displays, and communication antennas as well as for stabilizing biosensing materials and drug dispensing applications.