Light-adaptable artificial iris with dynamically scalable pupil-aperture function by radially patterned photochromic transition control

• Published in: Materials & design 2024-01, Vol.237, p.112515, Article 112515
• Main Authors: Nauman, Asad, Choi, Jun-Chan, Cho, Young-Min, Lee, Jae-Won, Kim, Hak-Rin
• Format: Article
• Language: English
• Subjects: Artificial iris; Gradient crosslinking polymer networks; Light-adaptable transmission; Photochromic switching; Scalable pupil-aperture
• ISSN: 0264-1275
• DOI: 10.1016/j.matdes.2023.112515

The iris is an ocular organ that actively controls the size of the pupil-aperture in response to external light, thereby regulating the amount of light reaching the retina for better visual acquisition. Herein, we propose a light-adaptive pupil-scalable artificial iris for addressing human iris defects with biomimetic self-regulating light control similar to human iris actuation, which is realized by a radially gradient and reversible photoswitching of photochromic dyes doped within a biocompatible hydrogel matrix. The radial photochromic switching of light transmissions was achieved by the gradient patterning of the crosslinking density of the hydrogel matrix using a near-infrared light-absorbing photomask that generated radially thermal gradience during hydrogel matrix polymerization. With the effective pupil-aperture control, the proposed artificial iris exhibited a variation in the visible-light transmittance from ∼82 % at the ultraviolet light (UV) intensity of 0.5 mW/cm2 to ∼43 % at 3.0 mW/cm2 representing the transparent and colored states, respectively. The switching times for the transitions to the colored and transparent states were 27.42 and 112.25 s, respectively, at a UV intensity of 3.0 mW/cm2, which can be faster under the hydrated state. The artificial iris demonstrated potential in biomedical applications by offering reliable light-adaptive attenuation control through human-like pupil-aperture adjustments.