| Summary: | 碩士 === 國立中正大學 === 化學暨生物化學研究所 === 104 === I. This work reports the integration efforts of capillary microchannel with the device of electro-wetting on dielectrics (EWOD). Using standard lithography processes, control electrodes are deposited on indium tin oxide (ITO) glass substrates, where Teflon film is then coated to work as dielectric and hydrophobic layer to develop the EWOD chip. The liquid is driven into the capillary using a syringe pump to form droplets hanging at the capillary outlet, which is 2.5 mm above the chip. When one drop falls on the chip to trigger the relays controlled by computer interfacing cards, the electrodes are activated in sequence to move the droplet. LabVIEW software package is used to develop controlling programs.
In our experiments, the 1 kHz AC voltage (150 Vrms) is applied to drive the droplets. When one droplet containing fluorescence particles falls on the EWOD chip, the fluorescence signals detected with photomultiplier tube are sent to control cards to switch the relays and divert the droplet to collection well. Otherwise, the non-fluorescent droplets are moved to waste well. The results indicate the particle sorting processes using this EWOD device are feasible with adequate accuracy.
II.Using micro- vortex driven by ionic wind generated near a corona needle tip above the liquid level of a small reservoir to provide centrifugal flows has been an emerging micro-fluidic technique to trap and concentrate suspended microparticles such as bacteria to detect. The surrounding air near the corona needle is ionized when high ac voltage is applied. The accumulated gas ions are repelled from each other at the needle tip to eject and produce ionic wind, which can swipe across the liquid air interface inside a miniaturized reservoir to generate centrifugal vortices, when the neelde is off the reservoir center. Suspended particles are further dragged into the reservoir center, where the vortex is more intense to trap at the reservoir bottom.
In this work, antigen-functionalized polystyrene micro-beads were conjugated with nanoaggregate-embedded beads (NAEB), made of silica-coated gold nano-particle aggregates doped with Raman reporter molecules, and immobilized with antibody probes to demonstrate particle concentrations at the stagnant point at the reservoir bottom by ionic wind-driven centrifugal flows in a reservoir containing 60 μL solution. Clear Raman scattering signals enhanced by gold nanoparticle plasmoncis were acquired from the particle concentrated spot to identify the trapped particles.
The ionic wind flows were also use to trap and concentrate Neisseria and Salmonella bacteria docked with antibody-functionalized NAEB at the level of 106 colony forming units (CFU) per ml or lower, when NAEB were doped with ethyl violet and fluorescein derivative, respectively. In addition to recognize concentrated bacteria by obtaining the Raman spectrum from the reporter molecules in NAEB, the linear relation between Raman scattering signal intensity and bacteria concentration was found from the concentration spot of NAEB-docked Salmonella over the range of 104 to 106 CFU per mL. This relation indicates the feasibility to quantify bacteria sample concentrations using this micro-centrifugal method.
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