A low sample volume particle separation device with electrokinetic pumping based on circular travelling-wave electroosmosis

Abstract

Particle separation is a crucial step in sample preparation processes. The preparation of low volume samples is especially important for clinical diagnosis and chemical analysis. The advantages of microfluidic techniques have lead them to become potential candidates for particle separation. However, existing microfluidic devices require external pumping sources and extensive geometric patterns to attain high separation efficiency, which is disadvantageous when handling low volume samples. This paper presents a low sample volume particle separation microfluidic device with low voltage electrokinetic pumping based on circular travelling-wave electroosmosis (TWEO). Computational numerical software was utilized to simulate two electrokinetic mechanisms: circular TWEO and dielectrophoresis (DEP). The circular TWEO shear flow generates a velocity gradient in the radial direction which causes a shear stress-induced force to drag particles into the center region of the device. In contrast, the non-parallel electrodes induce negative DEP forces which push polystyrene beads towards the peripheral regions; the magnitude of the DEP forces are dependent on the sizes of the polystyrene beads. We used particles of various sizes to experimentally prove the concept of particle separation. Our experiments show that 15 μm beads are dragged into the center region due to the shear stress-induced force, and 1 μm beads move towards the outer region because of the large negative DEP force. The results show a separation purity of 94.4% and 80.0% for 15 μm and 1 μm beads respectively. We further demonstrated particle isolation from a sample of containing a small proportion of 6 μm beads mixed with 1 μm beads at a concentration ratio of 1 : 300. Therefore, the innovative device developed in this paper provides a promising solution to allow particle separation in sample volumes as low as 50 nL.

Fabricating optical lenses by inkjet printing and heat-assistedin situcuring of polydimethylsiloxane for smartphone microscopy

“…4 PDMS has been employed to construct microfluidic devices since the 1990s, 5 and still maintains its wide applicability to date. [6][7][8][9][10] As a lens material, three types of fabrication techniques have been adopted: (1) lithographic methods, 11 (2) surface tension driven methods, 12 and (3) embossing methods. 13 These current approaches demonstrate the feasibility of creating PDMS lenses with good optical characteristics and reproducibility; however, they either require time-consuming fabrication procedures typically measured in hours, or have high costs due to lithographic and molding equipment required, and generally limit the size of the lens to the micrometer scale.…”

Dielectrophoresis for Biomedical Sciences Applications: A Review

“…The light intensity shifts in the central region of the dot were analyzed, and the DEP spectrum of the induced cells was plotted. While in [47], the circular electrode provided high separation efficiency without enlarging the device size. The particle separation method is based on non-uniform circular travelling-wave electroosmosis (TWEO).…”

Flow-Field-Assisted Dielectrophoretic Microchips for High-Efficiency Sheathless Particle/Cell Separation with Dual Mode

“…This sheathless aligner increased the sorting reproducibility for microfluidic devices. The ICEO-based prefocusing method can only focus cells into a stream at a low flow rate (<1 μL/min) and thus remains limited for the application in high-throughput sample processing. − DEP technique has also been applied to focus particles to two sides of a channel . Although these prefocusing methods combined with DEP can simplify the peripheral systems compared to the sheath flow method, the focusing region still needed to occupy a large space in the microchip.…”