A scratched contact lens usually means one thing, throw it out. Researchers in South Korea say that may not always be necessary.
Chemists Jung-Hyun Choi and Byoung-Ki Cho from Dankook University have developed contact lenses that can self-heal after an hour under ordinary ultraviolet light, according to research published in ACS Applied Polymer Materials.
The lenses use a hydrogel built around a disulfide cross-linker, a small molecule with a sulfur-to-sulfur bond that can form new attachments after being broken. The researchers combined the disulfide cross-linker with a methacrylate polymer. When a scratch breaks the physical connections between the polymers, ultraviolet light can reconnect them.
The team also added a second polymer to make the hydrogel more resistant to scratches and bacteria, then tested the material against a control hydrogel made with a standard cross-linker.
“In commercial hydrogel contact lenses, surface scratches caused by daily use or cleaning are far more common than complete cuts,” the researchers wrote.
“The DS-Hydrogel exhibited effective recovery of the surface scratches, whereas the Control-Hydrogel , which lacked the disulfide-based DS-Cross-linker, exhibited no visible healing under the same conditions.”
The team found the material could restore about 90 percent of its structural stability after damage. The study also found the new hydrogel had water retention on par with current soft lenses and showed strong scratch resistance.
“During contact lens wear, microscratches caused by blinking or routine cleaning can scatter light, causing glare, while also providing sites for protein or microbial adhesion, ultimately compromising ocular health,” the researchers wrote.
“Moreover, surfaces roughened by scratches and microcracks facilitate the adhesion and accumulation of proteins, increasing wearer discomfort and the risk of infection.”
The researchers said earlier examples of self-healing lenses needed temperatures much higher than room temperature. In this study, repair happened under ordinary ultraviolet light.
“This work details the synthesis, mechanical characterization, and functional evaluation of this disulfide-cross-linked hydrogel system and demonstrates its translation from hydrogel specimens to a practical molded contact lens format,” the researchers wrote.
“The combined self-healing capability, durable anti-fouling behavior, and enhanced scratch resistance highlight the potential of this disulfide-cross-linked hydrogel platform for next-generation functional contact lenses,” they wrote.
“Overall, the materials design strategy presented here provides a promising route toward long-lasting, resilient, and high-performance hydrogel-based ophthalmic devices.”
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