Surface acoustic wave actuated cell sorting (SAWACS)

Abstract

We describe a novel microfluidic cell sorter which operates in continuous flow at high sorting rates. The device is based on a surface acoustic wave cell-sorting scheme and combines many advantages of fluorescence activated cell sorting (FACS) and fluorescence activated droplet sorting (FADS) in microfluidic channels. It is fully integrated on a PDMS device, and allows fast electronic control of cell diversion. We direct cells by acoustic streaming excited by a surface acoustic wave which deflects the fluid independently of the contrast in material properties of deflected objects and the continuous phase; thus the device underlying principle works without additional enhancement of the sorting by prior labelling of the cells with responsive markers such as magnetic or polarizable beads. Single cells are sorted directly from bulk media at rates as fast as several kHz without prior encapsulation into liquid droplet compartments as in traditional FACS. We have successfully directed HaCaT cells (human keratinocytes), fibroblasts from mice and MV3 melanoma cells. The low shear forces of this sorting method ensure that cells survive after sorting.

On-chip manipulation of single microparticles, cells, and organisms using surface acoustic waves

“…To date, many acoustic-based particle manipulation functions (e.g., focusing, separating, sorting, mixing, and patterning) have been realized (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43). None of these approaches, however, have achieved the dexterity of optical tweezers; in other words, none of the previous acoustic-based methods are capable of precisely manipulating single microparticles or cells along an arbitrary path in two dimensions.…”

Optimisation of an acoustic resonator for particle manipulation in air

“…A high optical density is required for optical trapping, and the DEP method only operates over a limited spatial range. A third method, to be investigated here, uses forces generated by an ultrasonic field [14,15]. This technique, also known as acoustophoresis, can be integrated into small-scale devices to manipulate particles and droplets in both liquids and gases [16,17].…”

Droplet microfluidics: A tool for biology, chemistry and nanotechnology

“…Dominant interfacial and surface tension forces at small scales enable the precise generation and spatial stabilization of droplets. Droplet-based microfluidic systems can be fundamentally categorized into two basic designs: channel-based microfluidics in which the actuation occurs via liquid flows within microfabricated devices and the planar-surface approach where the actuation occurs through electrowetting or dielectrophoresis [4,9]. The planar-surface approach, sometimes called digital microfluidics, enables manipulation of discrete droplets on an array of electrodes [10].…”