Cell separation and transportation between two miscible fluid streams using ultrasound

Abstract

This paper presents a two-stream microfluidic system for transporting cells or micro-sized particles from one fluid stream to another by acoustophoresis. The two fluid streams, one being the original suspension and the other being the destination fluid, flow parallel to each other in a microchannel. Using a half-wave acoustic standing wave across the channel width, cells or particles with positive acoustic contrast factors are moved to the destination fluid where the pressure nodal line lies. By controlling the relative flow rate of the two fluid streams, the pressure nodal line can be maintained at a specific offset from the fluid interface within the destination fluid. Using this transportation method, particles or cells of different sizes and mechanical properties can be separated. The cells experiencing a larger acoustic radiation force are separated and transported from the original suspension to the destination fluid stream. The other particles or cells experiencing a smaller acoustic radiation force continue flowing in the original solution. Experiments were conducted to demonstrate the effective separation of polystyrene microbeads of different sizes (3 lm and 10 lm) and waterborne parasites (Giardia lamblia and Cryptosporidium parvum). Diffusion occurs between the two miscible fluids, but it was found to have little effects on the transport and separation process, even when the two fluids have different density and speed of sound.

Forces acting on a small particle in an acoustical field in a thermoviscous fluid

“…(16) and (18), and the linearity emphasized by the addition of subscripts "1" to the field variables. In this form, the thermoelastic equations (32) correspond to the fluid equations (17).…”

Microfluidic techniques for tumor cell detection

“…Active methods refer to the introduction of a kind of extra force field in the detection except the inertial force of the cells induced by flowing in a microchannel. These extra force fields can be generated by optical beams , electrodes , magnetic concentrators , and ultrasound . Conversely, if there is no extra force field, it is called the passive method.…”

Acoustophoretic microfluidic chip for sequential elution of surface bound molecules from beads or cells

“…It has previously been shown that acoustophoresis, 17 where acoustic forces are utilized, is highly effective for buffer medium transfer of particles or cells from complex biofluids. [18][19][20][21][22][23][24] Some benefits of this technique are: the rapid transverse motion of cells induced by the acoustic force (up to 1 mm s À1 ), 25 that the force depends on the intrinsic acoustic properties of the cell or particle, and that the microfluidic system design is straightforward and flexible.…”