A novel photonic-switch for biomolecular detection across the 10 nm gap via electro-wetting phenomena

Achieving complete wetting on nanophotonic devices is crucial for developing surface‐enhanced optical biosensors. However, ensuring complete wetting on solid surface of ultrafine nanoscale roughness becomes challenging owing to their water‐repellent properties. Korean researchers at Korea Institute of Science and Technology (KIST), and KU-KIST graduate School of Converging Science and Technolgy report the discovery of electrically‐induced wetting transition across the ultrafine nanogap on liquid‐permeable Fabry–Perot resonator for colorimetric refractive index sensing and switchable structural color with optical memory effects. The study appears in the journal Small in Febrary 2022.  

With narrow and dense nanoarchitectures increasingly adopted to improve optical functionality, achieving the complete wetting of photonic devices is required when aiming at underwater molecule detection over the water‐repellent optical materials. Despite continuous advances in photonic applications, real‐time monitoring of nanoscale wetting transitions across nanostructures with 10‐nm gaps, the distance at which photonic performance is maximized, remains a chronic hurdle when attempting to quantify the water influx and molecules therein. Work for leading-edge techniques, led by Prof. Yong-Sang Ryu, identified a novel photonic-switch for biomolecular detection across the 10 nm gap via electro-wetting phenomena. 

The researchers develops a photonic switch that transforms the wetting transition into perceivable color changes using a liquid‐permeable Fabry–Perot resonator. Electro‐capillary‐induced Cassie‐to‐Wenzel transitions produce an optical memory effect in the photonic switch, as confirmed by surface‐energy analysis, simulations, and an experimental demonstration. The results show that controlling the wetting behavior using the proposed photonic switch is a promising strategy for the integration of aqueous media with photonic hotspots in plasmonic nanostructures such as biochemical sensors.

Prof. Ryu said that "We showed for the first time the electro-wetting assisted photonic-switch that can monitor the real-time water-wetting behavior, with consequential memory effect. We also expect that our findings will provide a basis to develop a new small-molecule-based contraceptive in the future“, Prof. Ryu said.

Achieving complete wetting on nanophotonic devices is crucial for developing surface‐enhanced optical biosensors. 

[Main Author] 

1st Author:

Eui-Sang Yu (Brain Science Institute, Korea Institute of Science and Technology and Department of Electrical and Computer engineering, Seoul National university.)

Corresponding Author:

Yong-Sang Ryu (Brain Science Institute, Korea Institute of Science and Technology, KU-KIST graduate School of Converging Science and Technolgy)

* Contact email : Professor Yong-Sang Ryu (ysryu82@kist.re.kr)