A recently developed technique, acoustic force spectroscopy (AFS), allows the force manipulation of hundreds of single-molecules and single-cells in parallel, providing high experimental throughput. In this technique, a piezo element resonantly excites planar acoustic waves over a microfluidic chip. The generated acoustic waves are capable of exerting forces on microspheres with different density than the surrounding medium. Biomolecules, such as DNA, RNA or proteins, can be individually tethered between the microspheres and a surface and then probed by the acoustic forces exerted by the piezo sensor. With AFS devices it is possible to apply forces ranging from 0 to several hundreds of picoNewtons on hundreds of microspheres and obtain force-extension curves or histograms of rupture forces of many individual events in parallel.
This technique is mostly utilized to study DNA-bindings protein. For example, AFS was used to examine bacterial transcription with presence of antibacterial agents. Viral proteins also can be studied by AFS, for instance this technique was used to explore DNA compaction along with other single-molecule approaches.
Cells also can be manipulated by the acoustic forces directly, or by using microspheres as handles.