Fabrication of continuous flow microfluidics device with 3D electrode structures for high throughput DEP applications using mechanical machining

Abstract

Microfluidics is the combination of micro/nano fabrication techniques with fluid flow at microscale to pursue powerful techniques in controlling and manipulating chemical and biological processes. Sorting and separation of bio-particles are highly considered in diagnostics and biological analyses. Dielectrophoresis (DEP) has offered unique advantages for microfluidic devices. In DEP devices, asymmetric pair of planar electrodes could be employed to generate non-uniform electric fields. In DEP applications, facing 3D sidewall electrodes is considered to be one of the key solutions to increase device throughput due to the generated homogeneous electric fields along the height of microchannels. Despite the advantages, fabrication of 3D vertical electrodes requires a considerable challenge. In this study, two alternative fabrication techniques have been proposed for the fabrication of a microfluidic device with 3D sidewall electrodes. In the first method, both the mold and the electrodes are fabricated using high precision machining. In the second method, the mold with tilted sidewalls is fabricated using high precision machining and the electrodes are deposited on the sidewall using sputtering together with a shadow mask fabricated by electric discharge machining. Both fabrication processes are assessed as highly repeatable and robust. Moreover, the two methods are found to be complementary with respect to the channel height. Only the manipulation of particles with negative-DEP is demonstrated in the experiments, and the throughput values up to 105 particles / min is reached in a continuous flow. The experimental results are compared with the simulation results and the limitations on the fabrication techniques are also discussed.

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

“…10, the successful operation of both units is observed for case-3. For case-4, the successful operation for the wash unit is observed; however, the flow rate is observed to be too high for the separation unit to manipulate the microparticles (which is quite expected based on our previous study 29 ). The motivation for the wash unit is that the bio-particles are typically suspended in a highconductivity buffer solution.…”

“…29 Therefore, our previous design with 3D side-wall electrodes has been implemented in our integrated device. Following the ACP simulations, the length of the wash unit is selected as 30 mm, and the width of the channel is selected as 330 lm.…”

“…The 3D sidewall electrodes of the DEP section are placed manually at the side-wall as suggested in Ref. 29. During this process, to avoid the damage on the micro-channel, micro-channel needs to have some rigidity; therefore, metallic molds are a suitable option.…”

“…1 To achieve the throughput matching of ACP and DEP in the integration, 3D side-wall electrodes 29 are used for the DEP section. The experiments are performed using 5 lm polystyrene particles.…”

“…3D side-wall electrodes were fabricated using wire electric discharge machining. 29 With a unique mold design, the positioning of the two piezoelectric transducers (made of Lead Zirconate Titanate ceramic) and the 3D sidewall electrodes are accomplished during the molding process. The paper is organized as follows: In Section II, the computational model used in the design process is discussed.…”