Eur. Phys. J. Special Topics 223, 1937–1947 (2014)
https://doi.org/10.1140/epjst/e2014-02237-4

Regular Article

Opto-acoustic sensing of fluids and bioparticles with optomechanofluidic resonators

¹ Department of Mechanical Science and Engineering, The University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
² Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
³ Mechanical Engineering, Technion – Israel Institute of Technology, Technion City, Haifa 3200003, Israel

^a e-mail: bahl@illinois.edu

Received: 21 May 2014
Revised: 4 August 2014
Published online: 6 October 2014

Abstract

Opto-mechano-fluidic resonators (OMFRs) are a unique optofluidics platform that can measure the acoustic properties of fluids and bioanalytes in a fully-contained microfluidic system. By confining light in ultra-high-Q whispering gallery modes of OMFRs, optical forces such as radiation pressure and electrostriction can be used to actuate and sense structural mechanical vibrations spanning MHz to GHz frequencies. These vibrations are hybrid fluid-shell modes that entrain any bioanalyte present inside. As a result, bioanalytes can now reflect their acoustic properties on the optomechanical vibrational spectrum of the device, in addition to optical property measurements with existing optofluidics techniques. In this work, we investigate acoustic sensing capabilities of OMFRs using computational eigenfrequency analysis. We analyze the OMFR eigenfrequency sensitivity to bulk fluid-phase materials as well as nanoparticles, and propose methods to extract multiple acoustic parameters from multiple vibrational modes. The new informational degrees-of-freedom provided by such opto-acoustic measurements could lead to surprising new sensor applications in the near future.