On-chip simultaneous rotation of large-scale cells by acoustically oscillating bubble array.

Bubbles locating in microfluidic chamber can produce acoustic streaming vortices by applying travelling surface acoustic wave oscillation in an ultrasonic range, which can be used to drive bio-samples to move within the flow field. In this paper, a strategy of bubble array configured in a large number of regularly arranged horseshoe structures is proposed to capture and rotate cells simultaneously. By modifying the geometric parameters of the horseshoe structure and microfluidic setting, high bubble homogeneity and cell trapping percentage was achieved. The simulation and experimental results of the bubble-induced streaming vortices were confirmed to be consistent. Through experiments, we achieved both in-plane and out-of-plane rotation of arrayed HeLa cells trapped by the bubbles. Out-of-plane rotation was used to reconstruct the 3D (three-dimensional) cell morphology, which was demonstrated to be useful in calculating cell geometry related parameters. We believe that this bubble array based cell rotation method is expected to be a promising tool for the investigation of bioengineering, biophysics, medicine, and cell biology.