Yao Nan Wang

A hydrodynamic focusing microchannel based on micro-weir shear lift force

A novel microflow cytometer is proposed in which the particles are focused in the horizontal and vertical directions by means of the Saffman shear lift force generated within a micro-weir microchannel. The proposed device is fabricated on stress-relieved glass substrates and is characterized both numerically and experimentally using fluorescent particles with diameters of 5 μm and 10 μm, respectively. The numerical results show that the micro-weir structures confine the particle stream to the center of the microchannel without the need for a shear flow. Moreover, the experimental results show that the particles emerging from the micro-weir microchannel pass through the detection region in a one-by-one fashion. The focusing effect of the micro-weir microchannel is quantified by computing the normalized variance of the optical detection signal intensity. It is shown that the focusing performance of the micro-weir structure is equal to 99.76% and 99.57% for the 5-μm and 10-μm beads, respectively. Overall, the results presented in this study confirm that the proposed microcytometer enables the reliable sorting and counting of particles with different diameters.

Convenient quantification of methanol concentration detection utilizing an integrated microfluidic chip

A rapid and simple technique is proposed for methanol concentration detection using a PMMA (Polymethyl-Methacrylate) microfluidic chip patterned using a commercially available CO2 laser scriber. In the proposed device, methanol and methanol oxidase (MOX) are injected into a three-dimensional circular chamber and are mixed via a vortex stirring effect. The mixture is heated to prompt the formation of formaldehyde and is flowed into a rectangular chamber, to which fuchsin-sulphurous acid is then added. Finally, the microchip is transferred to a UV spectrophotometer for methanol detection purposes. The experimental results show that a correlation coefficient of R(2) = 0.9940 is obtained when plotting the optical density against the methanol concentration for samples and an accuracy as high as 93.1% are compared with the determined by the high quality gas chromatography with concentrations in the range of 2 ∼ 100 ppm. The methanol concentrations of four commercial red wines are successfully detected using the developed device. Overall, the results show that the proposed device provides a rapid and accurate means of detecting the methanol concentration for a variety of applications in the alcoholic beverage inspection and control field.

Microfluidic distillation chip for methanol concentration detection

An integrated microfluidic distillation system is proposed for separating a mixed ethanol-methanol-water solution into its constituent components. The microfluidic chip is fabricated using a CO2 laser system and comprises a serpentine channel, a boiling zone, a heating zone, and a cooled collection chamber filled with de-ionized (DI) water. In the proposed device, the ethanol-methanol-water solution is injected into the microfluidic chip and driven through the serpentine channel and into the collection chamber by means of a nitrogen carrier gas. Following the distillation process, the ethanol-methanol vapor flows into the collection chamber and condenses into the DI water. The resulting solution is removed from the collection tank and reacted with a mixed indicator. Finally, the methanol concentration is inversely derived from the absorbance measurements obtained using a spectrophotometer. The experimental results show the proposed microfluidic system achieves an average methanol distillation efficiency of 97%. The practicality of the proposed device is demonstrated by detecting the methanol concentrations of two commercial fruit wines. It is shown that the measured concentration values deviate by no more than 3% from those obtained using a conventional bench top system.

Particles small angle forward-scattered light measurement based on photovoltaic cell microflow cytometer.

A method is proposed for detecting microparticles in a microflow cytometer by means of small angle forward‐scattered light measurements. The proposed cytometer comprises a commercial photovoltaic cell, an adjustable power laser module, and a PDMS microfluidic chip. The detection performance of the proposed device is evaluated using particles with dimensions of 5, 8, 10, and 15 μm, respectively, given forward‐light scattering angles of 5 and 8° and laser powers ranging from 15–25 mW. It is shown that for a constant laser power and particle size, the S/N of the detected light signal increases with a reducing forward‐scattering angle. Moreover, for a constant forward‐scattering angle and particle size, the S/N increases with an increasing laser power. The intensity of the forward‐scattered light signal is found to vary linearly with the particle size and has a correlation coefficient of R2 = 0.967, 0.967, and 0.963 given laser powers of 15, 20, and 25 mW, respectively, and a forward‐scattering angle of 5°. Moreover, the CV of the forward‐scattered light intensity is found to lie within the range of 20–30% for both forward‐scattering angles. Overall, the present results suggest that the proposed device has significant potential for detection applications in the medical, environmental monitoring, and biological science fields

Numerical Simulation of Electromagnetic Actuator for Impedance Pumping

This study designs and analyzes an impedance pump utilizing an electromagnetic actuator. The pump is designed to have three major components, namely a lower glass substrate patterned with a copper micro-coil, a microchannel, and an upper glass cover plate attached a magnetic PDMS diaphragm. When a current is passed through the micro-coil, an electromagnetic force is established between the coil and the magnetic diaphragm. The resulting deflection of the PDMS diaphragm creates an acoustic impedance mismatch within the microchannel, which results in a net flow. Overall, the simulated results reveal that a net flow rate of 52.8 μl/min can be obtained using a diaphragm displacement of 31.5 μm induced by a micro-coil input current of 0.5 A. The impedance pump proposed in this study provides a valuable contribution to the ongoing development of Lab-on-Chips (LoCs) systems.

Rapid Detection of Methanol in an Integration Microfluidic Chip

A rapid and simple technique was developed for detecting methanol with very small amount of sample by using PMMA (Polymethyl-Methacrylate) microfluidic chip, which fabricated by a commercially available CO2 laser scriber. The experimental results indicate that linearity expression R2 can approximate 0.936 using the proposed integrating microfluidic chip when the 2 unit methanol oxidase (MOX) and basic fuchsin to detect methanol. Hence, the current device provides a valuable tool for rapid methanol detection, while its micro mixer system delivers a simple yet effective solution for mixing problems in the micro-total-analysis -systems field.

Effects of Heating Vents in a Tunnel-Type Dryer

This work employs FDS to simulate the heating process of a tunnel-type dryer and visualizes the computational results using Smokeview. The inappropriate design of a tunnel-type dryer in a factory has motivated this work. This poorly designed dryer not only has caused terrible fuel consumption but also produced parts some of which are under- or over-cooked. These are caused by the terribly uneven temperature distribution within the dryer. In order to improve the evenness of temperature distribution, this work simulates and investigates the effects of various ventilation schemes. Based on the results, it is found that the hot air intake vent should be placed at the bottom whereas the cold air outtake vent at the top. The flow rate through the intake vents does not have a very significant effect on the temperature distribution after 40 s.

Experimental investigation of high-resolution injection technique in microfluidic chips

This paper presents an experimental investigation on the use of high-resolution injection techniques to deliver sample plugs within electrophoresis microchips. Two novel injection microfluidic chips are proposed, which employ conventional cross-shaped and U-shaped injection system combined with an expander to deliver high-quality sample plugs for detection in separation channel. The valving characteristics on microfluidic devices are controlled through appropriate manipulations of the electric potential strengths during the sample injection and separation steps. These novel injection techniques developed in this study has an exciting potential for use in high-quality, high-throughput chemical analysis applications and in many other applications throughout the field of micro-total-analysis systems.