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Particles and cells can be patterned and moved (i.e., manipulated) precisely using acoustically driven techniques. To date, application of acoustic particle manipulation has been limited to plain surfaces. There is much potential for applying acoustic manipulation techniques to surfaces with microfabricated structures for high-throughput sensing. But adding thin film structures could alter manipulation characteristics compared to a plain surface. Using a two-chip setup that allows the wave generating device to be reused, we study the feasibility of acoustofluidic micro-manipulation on a surface-micromachined silicon (SMS) chip. The SMS chip is a complex superstrate with generic thin-film structures fabricated by patterning and etching multiple layers of thin films, with properties meant to represent a broad range of microfabricated devices. We report notable alterations in the particle separation distances on the SMS chip compared to a bare silicon superstrate, which we attribute to a change in wave type through a comparison of different superstrates prepared. We demonstrate a high cell viability after acoustic manipulation of live cells on the SMS chip. The results herein demonstrate the possibility of integrating a suite of microfabricated sensors on a chip with acoustically driven manipulation capabilities for multiplexed sensing and analysis for bio-applications.

Key to realizing practical resonators for liquid-phase sensing applications is efficient electromechanical transduction and reasonable ${Q}$ in liquid, which determine the motional resistance ( ${R}_{m}$ ). Both lower ${R}_{m}$ and high liquid phase ${Q}$ are important for realizing a more stable close-loop oscillator to allow a lower detection limit. But ${R}_{m}$ usually increases when scaling down resonator size, leading to weak output signals in liquid. This article describes a piezoelectrically transduced micromechanical elliptical plate resonator (EPR) targeting liquid-phase sensing applications. The proposed EPR delivers lower ${R}_{m}$ relative to other disk-based modes and has a reasonable ${Q}$ in water. These two features are critical for eventually realizing a closed-loop system to enable real-time frequency tracking for sensing applications. The low ${R}_{m}$ arises from enhanced transduction efficiency associated with the modal lateral strain profile. The EPR’s moderate liquid phase ${Q}$ stems from transducing a stiff lateral bulk mode that increases energy storage. The proposed EPR can be scaled down more efficiently compared to other disk-based modes in the limit of mode shape distortion by anchors when scaling down the resonator below a threshold. Experimental results in water are demonstrated for a $500~\mu \text{m}$ by $400~\mu \text{m}$ EPR, which delivers an ${R}_{m}$ of only 2.68 $\text{k}{\Omega }$ in water without feedthrough cancellation. Scaling down the device to $300~\mu \text{m}$ by $200~\mu \text{m}$ , we demonstrate an ${R}_{m}$ of just 5.5 $\text{k}\Omega $ and ${Q}$ of 245 in water. The proposed EPR topology boasts the lowest ${R}_{m}$ among resonators immersed in liquid after normalizing over the device area.