Hsiu-Hsiang Chen

Annealing effect of niobium pentoxide for low voltage electrowetting on dielectric (EWOD)

In this paper, the high dielectric constants for Nb2O5 (∼25.5) were deposited by a RF reactive magnetron sputtering and respectively annealed at 400 °C O2 ambiance for 30 min in a conventional furnace. Based on the results, an electrowetting optical deflector (EOD) filled with the water (1% sodium dodecyl sulfate (SDS)) and dodecane was fabricated and tested, and the contact angle of the inclined liquid surface on the left and right sidewall can be varied about 70° at 9 V operating voltage. This study provides a practical way to fabricate a high dielectric constant layer for low voltage electrowetting on dielectric (EWOD) application.

High-purity separation of cancer cells by optically induced dielectrophoresis

Abstract. Detecting and concentrating cancer cells in peripheral blood is of great importance for cancer diagnosis and prognosis. Optically induced dielectrophoresis (ODEP) can achieve high resolution and low optical intensities, and the electrode pattern can be dynamically changed by varied light patterns. By changing the projected light pattern, it is demonstrated to separate high-purity gastric cancer cell lines. Traditionally, the purity of cancer cell isolation by negative selection is 0.9% to 10%; by positive selection it is 50% to 62%. An ODEP technology is proposed to enhance the purity of cancer cell isolation to about 77%.

Optically-induced dielectrophoretic technology for cancer cells identification and concentration

The detection and concentration of cancer cells in peripheral blood is of great importance for cancer diagnosis and prognosis. Optically-induced dielectrophoresis (ODEP) can achieve high resolution and low optical intensities, and the electrodes pattern can be dynamically changed by varied light pattern. In this paper, a special lens is used to project the entire image to the ODEP chip to achieve 2.6×2 mm2 manipulating area. By changing projected light pattern, it is demonstrated to separate 10, 20, and 40μm PS (polystyrene) beads; HT-29, 20μm PS beads. The MCF-7 cells concentrated experiments are also demo at 100 μm/sec velocity.

Optically-induced dielectrophoretic technology for cells screening

The ODEP technology has many advantages such as low light energy (~10² W/cm²), virtual electrodes, large manipulating area and rapid screening of cells. In this paper, the 10 μm and 20 μm polystyrene beads are successfully separated by a 40 μm light line width with variable radius circle. Human colon cancer cells (HT-29) concentration experiments are demonstrated and can achieve at the maximum speed about 100 μm/sec.

Liquid Optic Deflector

The electrowetting-based optics has attracted a lot of interesting world wide recently. Several researchers have studied a variable focus liquid lens by using elecctrowetting. By tuning the applied voltage, they can change the shape of the liquid and the focal length. Heikenfeld et al. proposed an electrowetting microprism (EMP) and an angle tunable liquid wedge prism. However, the scale of the device mostly is in the order of millimeter and the manufcuring technology is by hand-assembly. As the switching-speed is proportioned to the size of device. It is difficult to assemble as the devices size is smaller than millimeter. It is urgently to develop manufacturing technologies for the micrometers device to improve the switching-speed. We proposed a liquid optic deflector (LOD), which combined two kinds of liquid in a cell. By using lithography and thin film technologies, we can fabricate the micro scale LOD. The incident light can be deflected by switching the electrode drive voltage of this liquid device. We applied 10 volts to let the water-oil boundary be level, and then applied the electrode drive voltage V1= -60 volts, V2= +60 volts of the liquid device, the tilt direction can be flipped into left direction. By switching the electrode drive voltage V1= +60 volts, V2= -60 volts of the liquid device, the tilt direction can be flipped into right direction, thus leading to an effective light deflection of the liquid prism effect by using tilt prism. We demonstrated liquid based scanners in 1-D scans with discrete scan beam spots. It is showed that the incident light can be deflected by switching the electrode drive voltage of this liquid device. This idea is the key to design of the different light beam scanning angle by using he discrete states of the applied voltage. In the liquid optic arrays experiment, we have use the lithography and thin film processes to make the prototype.

Optically-induced dielectrophoretic technology for particles manipulation and separation

The optically-induced dielectrophoretic (ODEP) technology has many advantages such as low light energy (~ 102 W/cm2), virtual electrodes, large manipulating area and rapid screening of cells. In this paper, 20 μm polystyrene beads are manipulated by a light circle and concentrated by a variable radius circle. The 10 μm and 40 μm polystyrene beads are successfully separated by a 40 μm light line width with vibrating beveled microfluidic light channels.

Electrowetting optical beam refractor

This paper systematically studies and demonstrates how to lower the operating voltage for an electrowetting optical beam refractor (EOBR). The results indicate that a low operating voltage can be achieved by decreasing the thickness of the dielectric layer and employing a higher dielectric constant, together with reducing the interfacial surface tension between the electrolyte and the surrounding ambient phase. The goal of this study was to explore various approaches to achieving a low operating voltage. First, two kinds of fluoropolymers (Teflon®AF1601 and Cytop®CTL-809M) were utilized to confirm the wettability. Second, Si3N4 dielectric layer with different thickness were tested to confirm the thickness and dielectric constant effect. Finally, three different surfactants (sodium dodecyl sulfate (SDS), Triton X100 and Triton X15) were used to confirm the interfacial surface tension effect. In this article, We demonstrate that the contact angle of water can change as much as 80° in a dodecane/water/Cytop®/Si3N4 system (containing 1% SDS) with an applied voltage as low as 14 V; furthermore, switchable apex angles of ≃± 20° and deflection of a beam passing through the meniscus of EOBR are presented.