Acoustic Tweezers for Manipulation and Analysis of Cells

The ability to manipulate cells is vital in many biological applications, be it sorting, phenotyping, or culturing. As cells are typically too small to handle with conventional mechanical means, a variety of manipulation techniques have been developed including optical tweezers, electromagnetic tweezers, and acoustic tweezers [1]. As a precise, non-contact, label-free and biocompatible manipulation method, acoustic tweezers possess some unique advantages over other micromanipulation techniques. While similar to optical tweezers, the increased force that can be exerted by acoustic tweezers allows them to manipulate cells, organoids, and even whole microorganisms. This has led to an array of biomedical applications for acoustic tweezers including cell focussing, sorting and patterning [2].

Despite a great amount of recent attention, there are still aspects of acoustic tweezers that are either poorly understood or have not yet been explored to their fullest potential. This project aims to build on the principles and applications of acoustic tweezers with a combination of mathematical modelling and experimental innovation and falls within the EPSRC engineering and mathematical sciences research areas. In particular, it will focus on the characterisation of cells, microswimmers, and the fluid flow involved in the acoustic trapping process. By exploring the combination of prescribed acoustic forces and hydrodynamic interactions between particles, I hope to gain insight into cell or organism properties as well as better understand mechanics such as flagellar beating or cilia movement. This has the potential to follow on to the creation of acoustically powered synthetic microswimmers or biohybrid designs, and even to computation and automated selection mechanisms. Investigating the hydrodynamic interactions of particles undergoing acoustic trapping also has the ability to enable novel methods for calibration of acoustofluidic devices and achieve a better understanding of some of the less well understood aspects of the acoustic radiation force.

Alongside research into the physics of acoustic devices, this PhD also aims to lower the barrier to entry into the making of microfluidic devices through the use of rapid prototyping processes. The majority of microfluidic devices are manufactured using lithographic techniques that often require extensive training and a clean room. Similarly, many acoustic resonator devices are constructed from wet etching of silicon or glass, another expensive process requiring clean room facilities. By employing rapid prototyping methods such as 3D printing and laser cutting throughout the PhD, I aim to refine processes for cheap and rapid manufacturing of acoustofluidic devices. This would greatly increase the suitability for acoustic tweezers as a tool point-of-care diagnostics.

Therefore, this project seeks to innovate and improve on the understanding and application of acoustic devices. Through new approaches to manufacturing, analytical, and experimental techniques, I aim to leverage the exciting technology of acoustic tweezers to new biomedical applications.

[1] A. Martinez-Rivas, G. K. González-Quijano, S. Proa-Coronado, C. Séverac, and E. Dague, "micromachines Methods of Micropatterning and Manipulation of Cells for Biomedical Applications", doi: 10.3390/mi8120347.
[2] B. W. Drinkwater, "A Perspective on acoustical tweezers-devices, forces, and biomedical applications," Applied Physics Letters, vol. 117, no. 18, p. 180501, Nov. 2020, doi: 10.1063/5.0028443.