Browsing by Author "Chen, Wen-Jung"

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Enhanced droplet mixer by LDEP on spiral microelectrodes
(2007)
Chiu, Cheng-Pu
;
Chen, Wen-Jung
;
Fan, Shih-Kang
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材料科學與工程學系奈米科技碩博班
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Graduate Program of Nanotechnology , Department of Materials Science and Engineering
We demonstrated a micromixer in which a liquid column was pumped in a virtual channel without channel walls by LDEP. Two droplets were first transported and joined together by EWOD actuation. The small contact area at the interface of the merged droplet and the long diffusion distance caused long mixing time by merely diffusion. A spiral-shaped LDEP electrode was designed to draw a thin liquid column from the merged droplet at the interface in order to increase the contact area and reduce the diffusion distance. Since no channel walls were required for LDEP pumping, the spiral-shaped liquid column would merge together again to form a new droplet for further analyses.
Reconfigurable liquid pumping in electric-field-defined virtual microchannels by dielectrophoresis
(2009)
Fan, Shih-Kang
;
Chen, Wen-Jung
;
Lin, Tin-Hsu
;
Wang, Tsu-Te
;
Lin, Yen-Chen
Dielectrophoresis (DEP), widely used to generate body forces on suspended particles, is investigated to provide surface forces at the liquid-medium interfaces and pump a high-permittivity liquid in a low-permittivity medium along a virtual microchannel defined by an electric field between parallel plates. Because the pumping pressure is proportional to the square of the intensity of the electric field and independent of the channel width, DEP pumping is advantageous as the dimension of the microchannel shrinks down. The absence of the channel walls simplifies the fabrication processes and further increases its feasibility in nanofluidic applications. We demonstrate water pumping in an immiscible silicone oil medium at adjustable velocities by applying voltages above the threshold value whose square is linearly proportional to the cross-sectional aspect ratio (AR), i.e., the height to width ratio, of the microchannel. With a properly designed AR, liquid valve is achieved by appropriate voltage applications. Without the barriers of channel walls, merging multiple streams and capillary filling of the spacing between electric-field-defined virtual microchannels are observed and studied. Moreover, in situ reconfigurable liquid pumping is demonstrated by a four way switching valve on a programmable crossing electrode set.
Virtual channel platform
(2010-07-15)
Fan, Shih-Kang
;
Chen, Wen-Jung
A virtual channel platform is disclosed. Said virtual channel platform comprises two electrode plates, which can provide an electric field, and two spacers set between said plates. Said plates are separated by said spacers for forming a passageway. A driven fluid is injected into said passageway. When applying electric signals of different frequencies in said plates, said plates form said electric field to drive said working fluid in a virtual channel.