Synthetic gel particle formation for acoustofluidic applications

Abstract: Cancer cell detection by particle sorting systems is a very challenging field which could help to discover cancers at an earlier stage. Acoustophoresis used as a particle sorting system is based on the difference between the acoustic properties of particles and the medium. Using a standing acoustic wave, the particles with the equivalent acoustic properties are focused at the same point in the channel. During the experiments on acoustophoresis systems some parameters can be adjusted such as the flow rate, the concentration, the frequency of the acoustic wave, etc. Microparticles such as silica-based, polystyrene and PMMA particles are mainly used as test particles to replace the cells. Artificial test particles have more defined properties enabling to repeat under the same conditions all experiments and have an easier handling. However, these particles are not reproducing very accurately the acoustic properties of human cells. Ideally, the test particles should have the same size and have acoustic properties as close to the cells that we want to investigate as possible. The work carried out in this project has been oriented around gel particles as a solution to replace the particles found on the market that are used as test particles in acoustofluidic systems. Agarose gel particles within the size range of the human cells have been produced using different microfluidic droplet generator chips. The gel particles was tested in acoustophoresis devices in a water medium and they interacted with the acoustic field. The smallest particles with a diameter of about $7-10$ $\mu m$ were circulating around in the vortices of the acoustic streaming. Some other gel particles had a motion towards the anti-node. Even if a real behavior of the particles in the water buffer has not been determined, it points to a possible way of producing gel test particles for a further use in acoustofluidic systems.