The Feasibility of Acoustophoresis Multimodal Control

Abstract: Actuating the acoustic resonance modes of a microfluidic device containing suspended particles (e.g., cells) allows for the manipulation of their individual positions. In this work, we investigate how the number of resonance modes $M$ chosen for actuation and the number of particles $P$ affect the probability of success $S$ of manipulation tasks, denoted Acoustophoretic Control Problems (ACPs). Using simulations, we show that the ratio of locally controllable volume to the state-space volume correlates strongly with $S$. This ratio can be efficiently computed from the pressure field geometry as it does not involve solving a control problem, thus opening possibilities for experimental and numerical device optimization routines. Further, we show numerically that in noise-free 1D systems $S \approx 1 - P/M$, and that in noisy 1D and 2D systems $S$ is accurately predicted by Wendel's Theorem. We also show that the relationship between $M$ and $P$ for a given $S$ is approximately linear, suggesting that as long as $P/M$ is constant, $S$ will remain unchanged. We validate this finding by successfully simulating the control of systems with up to $60$ particles with up to $600$ modes.