Over the past decade, remotely controlling the acoustic manipulation of cells in space within carrier matrices has emerged as a particularly promising approach for a wide range of applications, including chemical reaction control, microrobots, drug delivery, and cell and tissue engineering. Accurate control of cell positioning is a much-needed feature in tissue engineering applications, as it allows for a controlled filling of the matrix rather than relying on random seeding. Acoustic tweezers manipulate cells through the interaction of sound waves with solids, liquids, and gases, and can be used in almost any medium. Acoustic tweezers have advantages over magnetic tweezers that require magnetic particles.
Acoustic traps can be divided into body waves and surface waves. A surface acoustic wave (SAW) is an elastic acoustic wave that can only propagate on the surface of a substrate, with most of the energy concentrated at a surface depth of a few wavelengths. In recent years, SAW chips have been widely used for cell manipulation in microfluidic devices, providing a flexible method for single-cell localization. Interdigital transducers (IDTs) are commonly used to generate surface acoustic waves and are an important part of SAW chips. The resonant frequency of the surface acoustic wave can be controlled by adjusting the interdigital spacing of the electrodes, and the distribution of the sound field can be adjusted by changing the shape of the IDT.
Fig.1 Acoustic single-cell trapping method.
Creative Bioarray acoustic traps are capable of generating highly restricted and selective trapping paths of nearly arbitrary spatial complexity in open chambers without any internal structure. The spatial modes of our acoustic field are governed by shadowed waveguide structures located outside the chamber and can generate trapping and transmission geometries that are extremely difficult to produce only by sources on the chamber boundaries. Our acoustic capture is a dynamic single-cell patterning method that allows precise control of cell location, such as for controlling the morphology of nerve cells, forming individual neurites, and forming neural networks. Furthermore, we were able to capture cells at predetermined locations with acoustic tweezers and generate complex cellular patterns by using switching phases and manipulating different sets of transducers.