Contact\u00a0lenses are a great\u00a0vision correction\u00a0option\u00a0for many, but\u00a0if one of them gets damaged, there is little to do other than throw it away.\u00a0A\u00a0team reporting in\u00a0ACS Applied Polymer Materials\u00a0has a solution: special polymer\u00a0hydrogels and UV light.\u00a0Scratches on lenses made from their\u00a0new material\u00a0were\u00a0easily repaired with an hour of UV light exposure. This demonstration\u00a0is\u00a0a first step\u00a0toward\u00a0the next\u00a0generation of contact lenses.\u00a0<\/p>\n
Commonly used\u00a0“soft contacts” are made from hydrogels: porous, water-filled networks of polymers.\u00a0Hydrogel lenses\u00a0can be scratched or become cloudy\u00a0from\u00a0normal\u00a0wear\u00a0and\u00a0tear or\u00a0from\u00a0dust\u00a0and debris.\u00a0Currently,\u00a0there are no methods\u00a0for\u00a0repairing a contact lens once\u00a0it’s\u00a0damaged –\u00a0which can be annoying and expensive.\u00a0So,\u00a0Jung-Hyun Choi and Byoung-Ki Cho\u00a0wanted to develop a self-healing hydrogel material\u00a0for\u00a0repairable contact lenses.\u00a0<\/p>\n
Previously, the researchers created a hydrogel that repaired\u00a0itself after being heated for several hours; however, this was not ideal\u00a0for contact lenses\u00a0because\u00a0extended heating causes the\u00a0delicate\u00a0lens to dry out. So, this time they\u00a0used\u00a0UV light to\u00a0initiate\u00a0a\u00a0self-healing chemical reaction\u00a0at room temperature.\u00a0<\/p>\n
Choi and Cho built the\u00a0hydrogel using a disulfide cross-linker and\u00a0methacrylate polymer. Then\u00a0they\u00a0coated\u00a0it\u00a0with a different polymer to help prevent bacterial growth\u00a0and surface scratches.\u00a0When a damaged hydrogel\u00a0was\u00a0exposed to UV light (365 nanometers in wavelength) at room temperature for one hour, the energy from the light\u00a0induced a process known as disulfide exchange. Here,\u00a0existing sulfur-to-sulfur bonds break and form new bonds with other sulfur atoms,\u00a0slowly knitting the hydrogel back together. In tests, this\u00a0healing\u00a0process\u00a0was\u00a0highly\u00a0efficient, resulting in a near-seamless lens.\u00a0And, according to Cho, the repair process can be repeated\u00a0and could even be conducted using at-home UV lamps, such as\u00a0those used as\u00a0cleaning devices or\u00a0for curing gel nail polish.\u00a0<\/p>\n
In addition,\u00a0a lens formed from the coated hydrogel\u00a0had mechanical properties, including water retention,\u00a0similar to\u00a0those\u00a0expected for\u00a0soft\u00a0contacts.\u00a0The specialized anti-scratch coating even prevented\u00a0scratches from fine-grit sandpaper, dropping in transparency\u00a0only\u00a0by about 2%\u00a0after abrasion.\u00a0<\/p>\n
Before these lenses can be found on store shelves,\u00a0they’ll\u00a0need to go through\u00a0additional\u00a0stability testing and regulatory approval. But the researchers hope that this work\u00a0could\u00a0lead to\u00a0contact lenses that\u00a0are more robust.\u00a0<\/p>\n
Source:<\/p>\n
American Chemical Society<\/a><\/p>\n Journal reference:<\/p>\n