Papers by Author: Wei Wang

Abstract: This paper puts forward a kind of two benches structure of the glass-PDMS free flow electrophoresis chip. We use die casting method to produce microstructure, and use PDMS as its structure layer. The mold is made in tape-PMMA by micro cementing technology. During the progress of PDMS curing, gold wires are directly integrated in the electrode groove to form the chips electrodes. PDMS and glass are sealed in natural bonding method. Chips glass surface of separation chamber realizes the modification through sticking polyimide tape. Visual technology is conducted for chip electrophoresis separation. The sample is the mixture of methyl green and Rhodamine B. The separation effect of methyl green and Rhodamine B is obvious when the electric field is 31 V/cm. the "two benches" between the electrode groove and the separation chamber block the electrolytic bubbles into the separation chamber. When the separation chamber height is 70 μm and the electric field is 50 V/cm, the air bubbles can be glidingly discharged from electrode groove. The samples steady separation time is more than 2 hours, and this free flow electrophoresis chip realizes continuous work.

Abstract: We research removable electrodes based on microfluidic chip in this paper. The electrodes can be assembled and fixed quickly and easily. We could change toxic electrodes conveniently during experiment. In addition the design of removable electrodes fits different size of channels, because the detection electrodes could be set its position close to outlet of microchannel under the microscope. We provide numerical simulations of COMSOL and hotomicrographs to proving our design in this article.

Abstract: UV radiation, oxygen plasma treatment and dynamical coating technique were the three main modification techniques to be widely applied in the surface modification of polymer materials. This paper presented the experiment results of PDMS surface modification with these three techniques. The contact angle was measured to test the modification effect, also the further verification testing of aging property after a long time storage were carried out. Of all the testing results, the dynamical coating technique, 10 layers 0.02% PDDA and PSS (V/V) alternatively adhesion on the PDMS surface, made the contact angle lowed to the 21°, and even after 15 days, it still kept as the 61°and exhibited the better hydrophilic character.

Abstract: This paper presents a portable miniaturized integration UV-VIS absorbance detection system for the microchip electrophoresis (MCE). The TOCON_nano high sensitive SiC pre-amplified UV Sensor (Sglux GmbH, Ostendstrasse, Berlin, Germany) is used to measure extremely low UV radiation intensities in the nanowatt scale. This detection system volume is 280 ×200×150 mm³, the weight is less than 2Kg. The PMMA was used as the MCE substrate materials. And the electrophoresis microchannels are fabricated with the CNC milling, have the cross section area of 150μm ×150μm. With this detection system, the detection limit for the Cl- electrophoresis can reach 10^-10mol at the indirect UV-VIS detection mode. Two ino^{Superscript text}rganic ions Cl^- and SO₄^2- could reach the baseline separation in 3 min.

Abstract: A new manufacture mainly for polymethyl methacrylate (PMMA) microfluidic chips is presented in this paper. In this technique, polymer microfluidic microchannels were fabricated by microcutter which temperature is controlled and stabilized by PID methord. There are so many techniques, such as hot embossing, laser direct-write, for mass-production of polymer microfluidic chip. However, we may feel different kinds of shortages when we use these techniques. In this paper, the experiment result shows that microcutter’s movement velocity and temperature have effert on microfluidic microchannel’s roughness.

Abstract: The orifice which formed by the sudden change of channel’s scale on microfluidic chip and its application have introduced in this paper. The characteristics of orifice flow on microfluidic chip are studied by μ-PIV technology. The experimental PDMS chip is fabricated by hot press molding. The transient flow field experiment is carried out on the μ-PIV platform. The flow of thin-walled/thick-walled orifice was measured in experiment. There is flow constriction of orifice flow in jet state; the flow constriction of thick-walled orifice can pump the liquid in channel; and the critical Reynolds number of jet flow in microchannel structure is 190.

Abstract: Multi-wall Carbon Nanotubes (MWNTs) is the new hotspot material as the active sensing element, but there is no certain theory on the phenomenon of the vapor's capillary condensation in MWNTs for the present. This paper presents a new theory that the capillary condensation of vapor in MWNTs mostly occur in the internal hollow tube, according to the calculation of equivalent model of MWNTs. A kind of carbon nanotubes (CNTs) humidity sensor based on quartz crystal microbalance was fabricated, CNTs employed as adsorption materials. The sensor was put in 11% and 97% relative humidity environment in experimental, and the value of M_H2O/M_CNT was calculated. The theory in this paper is proved by the comparison between the experimental and the analysis results.

Abstract: PMMA, Capillary Electrophoresis, Thermal bonding, Factor, Deformation. Abstract. In this paper, using the powder hot embossing machine, the effects of the bonding temperature, pressure and time on the deformation of microchannel dimensions is studied systematically. The bonding temperature is mainly influence factor on the deformation of microchannel determined by the method of orthogonal experiment. Some mathematical models are described to optimize the thermal bonding process parameters. According theory and experimental curve, the optimal experimental model (83°C, 0.4Mpa and 7 min) is suggested. Under the process parameters the deformation of crossing section dimension before and after thermal bonding is 37.8%. The channel is successfully sealed underneath with a thin foil 30μm thickness PMMA for contactless conductivity detection. The entire fabrication methodology may also be useful for preparation of other polymer microfluidic systems. Finally, the performance of the PMMA chip is demonstrated to separate continuously K+ ions using the contactless conductivity detection.

Abstract: A new low cost high performance PMMA micropump, developed for microfluidic system, is presented. According to the orifice flow theory, a diffuser/nozzle structure is fabricated with precision milling process, and packaged with the film-sealing at the condition of thermal bonding process. The size parameter of the diffuser/nozzle structure is 2.5mm *150µm, 8° conical angle, the volume of PMMA micropump is 14×14×2.5 mm3. And experimental results show that the PMMA micropump can produce a maximum back pressure of 1906.1Pa and a maximum flow rate of 564µL/min under 220 V, 500Hz squired wave power supply.