Laser-guided acoustic tweezers

TL;DR

This paper introduces a simplified design for microscale acoustic tweezers that leverages nonlinear acoustic forces generated by synchronized electro- and photo-acoustic waves, enabling stronger and more precise manipulation of microscopic objects.

Contribution

It demonstrates a novel hybrid acoustic trapping method combining electro- and photo-acoustic waves to enhance force strength and resolution in acoustic tweezers.

Findings

Hybrid acoustic trapping force is 30 times stronger than laser alone.

Interference of electro- and photo-acoustic waves enhances spatial control.

New approach enables better cell manipulation in biomedical applications.

Abstract

Acoustic tweezers can manipulate microscopic objects and cells independently of the optical, magnetic and electrical properties of the objects or their medium. However, because ultrasonic waves are attenuated within few millimeters, existing devices must synthesize intricate and powerful acoustic fields in a very narrow footprint immediately close to the manipulated object. Here we show that the design of microscale acoustic tweezers can be considerably simplified by taking advantage of the nonlinear nature of the acoustic trapping force. In our experiment, a featureless piezoelectric crystal coated with a photoacoustic conversion layer is hit by an electric pulse and a spatially modulated laser pulse to generate synchronized electro- and photo- acoustic waves. Interference between these waves creates a hybrid acoustic trapping force 30 times stronger than the laser pulse alone but with the same spatial information. By disentangling the tradeoff between spatial resolution and trapping force that has long held back the development of acoustic tweezers, this field hybridization strategy opens new avenues for cell manipulation in organ on chip and organ printing.