Regenerative medicine has the capability to revolutionise many aspects of medical care, but for it to make the step from
small scale autologous treatments to larger scale allogeneic approaches, robust and scalable label free cell sorting
technologies are needed as part of a cell therapy bioprocessing pipeline. In this proceedings we describe several
strategies for addressing the requirements for high throughput without labeling via: dimensional scaling, rare species
targeting and sorting from a stable state. These three approaches are demonstrated through a combination of optical and
ultrasonic forces. By combining mostly conservative and non-conservative forces from two different modalities it is
possible to reduce the influence of flow velocity on sorting efficiency, hence increasing robustness and scalability. One
such approach can be termed "optically enhanced acoustophoresis" which combines the ability of acoustics to handle
large volumes of analyte with the high specificity of optical sorting.
We report the combined use of optical sorting and acoustic levitation to give particle sorting. Differing sizes of microparticles are sorted optically both with and without the aid of acoustic levitation, and the results compared to show that the use of acoustic trapping can increase sorting efficiency. The use of a transparent ultrasonic transducer is also shown to streamline the integration of optics and acoustics. We also demonstrate the balance of optical radiation pressure and acoustic levitation to achieve vertical sorting.