3D printing holds great potential for the customized production of contact lenses, including advanced multi-material and multifunctional contact lenses. However, there are limitations in the geometrical accuracy and surface quality of 3D-printed contact lenses because of issues such as overcure and staircase effect. This study aims to develop 4D printing techniques to overcome these challenges.
Controlled warpage and bilayer hydrogel actuation are explored as two 4D printing techniques for contact lenses. In both techniques, a flat disk with radial apertures is printed, which then turns into a curved lens after printing. While the warpage technique uses differences in curing between two sides of a contact lens for shape change, bilayer actuation uses differences in swelling between two layers of material within the lens. The two techniques are investigated with different hydrogel combinations and sample thicknesses.
Flat disks with radial apertures curve because of warpage and bilayer actuation, forming a shape similar to contact lenses. The bilayer actuation technique offers better reliability and control over the curvature compared to warpage. In both cases, 4D printing enhances surface quality and reduces print time. Further, these techniques offer increased flexibility in the production of multi-material and multifunctional contact lenses.
This study highlights the utility of 4D printing for simpler and faster production of advanced contact lenses. With further optimization, 4D printing techniques can facilitate the rapid and efficient production of next-generation contact lenses.
