An integrated acoustic and dielectrophoretic particle manipulation in a microfluidic device for particle wash and separation fabricated by mechanical machining

Abstract

In this study, acoustophoresis and dielectrophoresis are utilized in an integrated manner to combine the two different operations on a single polydimethylsiloxane (PDMS) chip in sequential manner, namely, particle wash (buffer exchange) and particle separation. In the washing step, particles are washed with buffer solution with low conductivity for dielectrophoretic based separation to avoid the adverse effects of Joule heating. Acoustic waves generated by piezoelectric material are utilized for washing, which creates standing waves along the whole width of the channel. Coupled electro-mechanical acoustic 3D multi-physics analysis showed that the position and orientation of the piezoelectric actuators are critical for successful operation. A unique mold is designed for the precise alignment of the piezoelectric materials and 3D side-wall electrodes for a highly reproducible fabrication. To achieve the throughput matching of acoustophoresis and dielectrophoresis in the integration, 3D side-wall electrodes are used. The integrated device is fabricated by PDMS molding. The mold of the integrated device is fabricated using high-precision mechanical machining. With a unique mold design, the placements of the two piezoelectric materials and the 3D sidewall electrodes are accomplished during the molding process. It is shown that the proposed device can handle the wash and dielectrophoretic separation successfully.

FIG. 1.

Schematic drawing of the integrated microfluidic device.

FIG. 2.

Computational domain: (a) Without PZT actuator (case-A), (b) PZT actuators are at the side-walls (case-B), and (c) PZT actuators are on the top (case-C).

FIG. 3.

Acoustic pressure distribution in the width direction of the channel evaluated at 25 different locations along the channel: (a) case-A, (b) case-B, and (c) case-C.

FIG. 4.

Particle trajectories along the channel: (a) case-A, (b) case-B, and (c) case-C.

FIG. 5.

Drawing of the mold.

FIG. 6.

Streamlines in the wash unit for different volumetric flow rates.

FIG. 7.

Fabricated brass mold, PZT actuators and electrode assembly, and the final device.

FIG. 8.

(a) Experimental set-up and (b) blown-up figure for the microfluidic device.

FIG. 9.

Particle trajectories (case-1).

FIG. 10.

Particle trajectories: (a) case-3 and (b) case-4.

FIG. 11.

Particle trajectories for the experiment with p-DEP (half-coated) and n-DEP (uncoated) latex particles.