Browsing by Author "Huang, Po-Wen"

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Cross-scale electric manipulations of cells and droplets by frequency-modulated dielectrophoresis and electrowetting
(2008-08-01)
Fan, Shih-Kang
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Huang, Po-Wen
;
Wang, Tsu-Te
;
Peng, Yu-Hao
;
材料科學與工程學系奈米科技碩博班
Two important electric forces, dielectrophoresis (DEP) and electrowetting-on-dielectric (EWOD), are demonstrated by dielectric-coated electrodes on a single chip to manipulate objects on different scales, which results in a dielectrophoretic concentrator in an EWOD-actuated droplet. By applying appropriate electric signals with different frequencies on identical electrodes, EWOD and DEP can be selectively generated on the proposed chip. At low frequencies, the applied voltage is consumed mostly in the dielectric layer and causes EWOD to pump liquid droplets on the millimetre scale. However, high frequency signals establish electric fields in the liquid and generate DEP forces to actuate cells or particles on the micrometre scale inside the droplet. For better performance of EWOD and DEP, square and strip electrodes are designed, respectively. Mammalian cells (Neuro-2a) and polystyrene beads are successfully actuated by a 2 MHz signal in a droplet by positive DEP and negative DEP, respectively. Droplet splitting is achieved by EWOD with a 1 kHz signal after moving cells or beads to one side of the droplet. Cell concentration, measured by a cell count chamber before and after experiments, increases 1.6 times from 8.6 x 10(5) cells ml(-1) to 1.4 x 10(6) cells ml(-1) with a single cycle of positive DEP attraction. By comparing the cutoff frequency of the voltage drop in the dielectric layer and the cross-over frequency of Re(f(CM)) of the suspended particles, we can estimate the frequency-modulated behaviors between EWOD, positive DEP, and negative DER A proposed weighted Re(f(CM)) facilitates analysis of the DEP phenomenon on dielectric-coated electrodes.
Reflective electronic paper display utilizing electric polarized particle chains
(2007)
Chiu, Cheng-Pu
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Huang, Po-Wen
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Fan, Shih-Kang
;
Wei, Jen-Hung
;
Hsu, Wensyang
We demonstrated a display technique by applying an AC field to polarize the originally evenly dispersed microparticles in liquid solution. The polarized particles would attract each other and form particle chains along the field lines. As a result, the light transmittance of the liquid can be regulated as a reflective display.
Transmittance tuning by particle chain polarization in electrowetting-driven droplets
(2010-12-01)
Fan, Shih-Kang
;
Chiu, Cheng-Pu
;
Huang, Po-Wen
;
材料科學與工程學系
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Department of Materials Science and Engineering
A tiny droplet containing nano/microparticles commonly handled in digital micro-fluidic lab-on-a-chip is regarded as a micro-optical component with tunable transmittance at programmable positions for the application of micro-opto-fluidic-systems. Cross-scale electric manipulations of droplets on a millimeter scale as well as suspended particles on a micrometer scale are demonstrated by electrowetting-on-dielectric (EWOD) and particle chain polarization, respectively. By applying electric fields at proper frequency ranges, EWOD and polarization can be selectively achieved in designed and fabricated parallel plate devices. At low frequencies, the applied signal generates EWOD to pump suspension droplets. The evenly dispersed particles reflect and/or absorb the incident light to exhibit a reflective or dark droplet. When sufficiently high frequencies are used on to the nonsegmented parallel electrodes, a uniform electric field is established across the liquid to polarize the dispersed neutral particles. The induced dipole moments attract the particles each other to form particle chains and increase the transmittance of the suspension, demonstrating a transmissive or bright droplet. In addition, the reflectance of the droplet is measured at various frequencies with different amplitudes. (C) 2010 American Institute of Physics. [doi:10.1063/1.3516656]
Transmittance tuning by particle chain polarization in electrowetting-driven droplets
(2010-12-01)
Fan, Shih-Kang
;
Chiu, Cheng-Pu
;
Huang, Po-Wen
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A tiny droplet containing nano/microparticles commonly handled in digital micro-fluidic lab-on-a-chip is regarded as a micro-optical component with tunable transmittance at programmable positions for the application of micro-opto-fluidic-systems. Cross-scale electric manipulations of droplets on a millimeter scale as well as suspended particles on a micrometer scale are demonstrated by electrowetting-on-dielectric (EWOD) and particle chain polarization, respectively. By applying electric fields at proper frequency ranges, EWOD and polarization can be selectively achieved in designed and fabricated parallel plate devices. At low frequencies, the applied signal generates EWOD to pump suspension droplets. The evenly dispersed particles reflect and/or absorb the incident light to exhibit a reflective or dark droplet. When sufficiently high frequencies are used on to the nonsegmented parallel electrodes, a uniform electric field is established across the liquid to polarize the dispersed neutral particles. The induced dipole moments attract the particles each other to form particle chains and increase the transmittance of the suspension, demonstrating a transmissive or bright droplet. In addition, the reflectance of the droplet is measured at various frequencies with different amplitudes. (C) 2010 American Institute of Physics. [doi:10.1063/1.3516656]