Surface Sensitive Microfluidic Optomechanical Sensors

TL;DR

This paper investigates the surface sensitivity of a microfluidic optomechanical resonator (uFOMR) by measuring frequency shifts caused by layer-by-layer SiO2 removal, demonstrating its potential for surface molecule detection.

Contribution

It introduces a method to quantify surface sensitivity of uFOMR using controlled SiO2 removal and measures its detection limit for surface molecules.

Findings

Sensitivity of 1.2 Hz/(pg/mm2) for surface changes

Detection limit of 83 pg/mm2 for surface density

Potential for molecule detection near the resonator surface

Abstract

The microfluidic optomechanical resonator (uFOMR) based on a thin-walled glass capillary supports high Q-factor (>1000) mechanical modes in the presence of liquids. In this Letter, the sensitivity of the uFOMR to the surface change is studied by layer-by-layer removal of SiO2 molecules from the uFOMR inner surface using various concentrations of hydrofluoric acid solutions. A frequency downshift is observed with a sensitivity of 1.2 Hz/(pg/mm2), which translates to a surface density detection limit of 83 pg/mm2. This work opens a door to using the optomechanical mode for detection and characterization of molecules present near the resonator surface.