South Korean research team has developed nano-optical device that can be combined with biological tissue and inserted into a human eyeball. This device can be applied to wireless intraocular pressure detection sensor and ocular insert for improving eyesight.
Research team led by Professor Kim Sung-hwan of Ajou University announced on the 21st that it has developed 3D photonic crystal device that has similar properties as biological tissues by utilizing natural silk protein that is extracted from cocoons.
Photonic crystal is a structure that has matters with different refractive indexes periodically arranged in order to control light. Photonic crystal device can be inserted into an eyeball safely as it is harmless to human body.
Silk protein from a cocoon is harmless to human body and is transparent and strong. It is seen as a material that can assist in making attachable and insert-type device for a human body. However because it is easily dissolved in water, it was difficult to make a device that will work in a moist environment such as human tissues.
Research team combined stilbene dye, which play a role of photoinitiator, with aqueous solution of silk protein (fibroin). Afterwards it applied UV ray and formed (photopolymerization) strong union between molecules and made 3D photonic crystal with silk protein that is formed from this process.

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<Pictures of epidemiological change of silk photonic crystal device. Even when it is stretched, bent, and compressed by external force, it works normally.>

Research team made ‘hydrogel’ photonic crystal structure that remains moisturized and not dissolved in water under moist environment. While it is elastic and flexible, it does not dissolve in water and it can be easily combined with body tissue without any sense of difference. Research team has overcome limitations of current materials and implemented safe photonic crystal structure even when it is inserted into human body.
Research team was able to confirm that its device can be used as a wireless intraocular pressure detection sensor. Optical band gap of this device changes due to external force and can be measured remotely and in real-time with simple equipment. When this device is inserted into an eyeball, it will measure values that change depending on intraocular pressure.
This device can be used as an ocular insert to improve eyesight. Research team carried out a trial test that integrates silk photonic crystal to surface of an eyeball model and confirmed that light that escapes from an eyeball to outside is reflected back to inside.
Research team predicts that visual cells from retina will absorb light 30% more and this will lead to improvement in eyesight. This is same principle as how nocturnal or deep-sea animals, which have tapetum lucidum, have excellent sensitivity towards light and excellent eyesight.
“We have developed world’s first nano-optical device that can be combined with biological tissue.” said Professor Kim Sung-hwan. “This device can be applied to healthcare fields such as measurement of intraocular pressure’s wireless optical signal and ocular insert for improving eyesight.”
Result of this research was published on an international scientific journal called PNAS (Proceedings of the National Academy of Sciences). This research was supported by X-Project Support Project from Ministry of Science, ICP and Future Planning and National Research Foundation of Korea and Ministry of Education’s Science & Engineering Personal Basic Research Support Project.
Staff Reporter Song, Junyoung | songjy@etnews.com