Towards highly specific measurement of binary mixtures by tandem operation of nanomechanical sensing system and micro-Raman spectroscopy

Abstract

Nanomechanical sensing with suspended microchannel resonator (SMR) has been effectively applied to measure density and viscosity of pure liquids and volume contraction of binary mixtures to date. To enhance specificity, it is necessary to combine additional independent measurements. In this paper, we propose an integrated system of nanomechanical sensing with SMR and micro-Raman spectroscopy that is used to differentiate binary mixtures with same density and viscosity by measuring mole fraction. By density and viscosity measurements with SMR for ethanol-water (H2O), ethanol-glycerol, and ethanol-heavy water (D2O) binary mixtures, ethanol-H2O and ethanol-glycerol mixtures can be differentiated while ethanol-H2O and ethanol-D2O mixtures cannot be differentiated. Towards highly specific measurements, micro-Raman spectroscopy is configured on top of the SMR. Ratiometric analysis of Raman spectra (RARS) from sample and substrate accurately provides the mole fraction of different binary mixtures and differentiates ethanol-H2O and ethanol-D2O mixtures. The average and maximum differences between measured mole fractions and the reference values are about 1.0% and 2.4%, respectively.