Quality Factor Enhancement of Lateral Microresonators in Liquid Media by Hydrophobic Coating

In this letter, a new method of improving the quality factor of microresonators inside liquids is presented. By utilizing a conformally coated thin layer of parylene, which is highly hydrophobic, we trap air between the narrow gaps of a lateral resonator and prevent liquids from entering the gaps, thus preventing the viscous damping increase on the side surfaces. Initial tests with capacitive comb drives show that the quality factor decreases only threefold (from 157 to 55) when the device is operated in water after parylene coating. This method is very promising for in-liquid resonator applications, particularly real-time bioagent detection where high quality factor is essential for high mass resolution.