Measuring the Resonances of Nanopillars through Surface Acoustic Waves

Abstract

Abstract—Resonant mass sensors are emerging as innovative instruments for particle measurement, which utilize the resonance frequency shifts of oscillatory structures. Micro- and nano-pillars have been adopted as the resonators for the high sensitivity of this mass sensing technique. However, existing frequency measurement methods for micro- and nano-mechanical resonators are mostly based on piezoresistive readouts, which were challenged for the integration of such small structures as submicron pillars. In this paper, aluminum nitride surface acoustic wave (SAW) delay line devices were utilized to investigate the potential for measuring the resonance frequencies of several micro/nano-pillars simultaneously. SAW delay line devices for this resonance measuring application have been successfully designed, fabricated, and tested. Both two-photon polymerized (TPP) pillars and focused ion beam (FIB) deposited pillars have been incorporated into the delay line devices. COMSOL simulations in this work have demonstrated the feasibility of multi-resonance measurements. Small peaks, likely corresponding to pillar resonances, were detected and showed some correlation with the resonances. These results suggest that using SAW delay lines is a promising technique for multi-resonance detection of nanopillar arrays. This work paved the way for high-sensitivity
mass sensor development with effective SAW devices and methods of incorporating pillars.