C.K. Chung

Microfluidic chip for plasma separation from undiluted human whole blood samples using low voltage contactless dielectrophoresis and capillary force

A plasma separating biochip is demonstrated using a capillary-driven contactless dielectrophoresis method with low voltage (~1 V) and high frequency induced electrostatics between red blood cells. The polarized red blood cells were aggregated and separated from plasma with a 69.8% volume separation and an 89.4% removal rate of red blood cells.

A Facile Method and Novel Mechanism Using Microneedle‐Structured PDMS for Triboelectric Generator Applications

The triboelectric generator (TEG) is a cost-effective, multi-fabricated, friendly mechanical-energy-harvesting device. The traditional TEG, generally formed by two triboelectric materials in multilayers or a simple pattern, generated triboelectricity as it worked in the cycling contact-separation operation. This paper demonstrates a novel, high-aspect-ratio, microneedle (MN)-structured polydimethylsiloxane (PDMS)-based triboelectric generator (MN-TEG) by means of a low-cost, simple fabrication using CO2 laser ablation on the polymethyl methacrylate substrate and a molding process. The MN-TEG, consisting of an aluminum foil and a microneedle-structured PDMS (MN-PDMS) film, generates an output performance with an open-circuit voltage up to 102.8 V, and a short-circuit current of 43.1 µA, corresponding to the current density of 1.5 µA cm-2 . With introducing MN-PDMS into the MN-TEG, a great increase of randomly closed bending-friction-deformation (BFD) behavior of MNs leads to highly enhanced triboelectric performance of the MN-TEG. The BFD keeps increasingly on in-contact between MN with Al that results in enhancement of electrical capacitance of PDMS. The effect of aspect ratio and density of MN morphology on the output performance of MN-PDMS TEG is studied further. The MN-TEG can rapidly charge electric energy on a 0.1 µF capacitor up to 2.1 V in about 0.56 s. The MN-TEG source under tapping can light up 53 light-emitting diodes with different colors, connected in series.

Simulation and experiment of capillary driven passive planar baffle micro-mixer

In this study, we present a capillary driven and easily fabricated passive planar baffle micro-mixer with a trigger valve. The micro-mixers were fabricated in PMMA sheets (2 mm in thickness) by CO2 laser ablation and thermal bonding, and the microfluidic experiments were observed and recorded using flow visualization with a CCD. The results show that design of channel height ranges (to 220~400 μm) can be promoted by modifying the staggered baffle structure, and the meander baffle structure mixer performs the best mixing efficiency (94%) because of longest flow time and shortest average diffusion distance (300 μm) in mixing zone.

Fabrications of Electroless Ni-P Composite Coatings before and after Annealing and Tribological Analyses

In the present study, SiC reinforced particles were introduced to the Ni-P plating bath, and developed high SiC content composite coatings. Thin films nature properties and mechanical performances were evaluated well. The results showed that the Ni-P alloy embedded SiC particles formed a few cavities, and reduced coatings hardness and wear resistance in as-plated condition. After 400°C heat-treatment, Ni3P crystalline phase formed and reached the max hardness, and conducted excellent trybological performances. SiC particles were decoposited in 600°C and reacted with Ni to form Ni3Si and Ni5Si2, caused the decreasing in hardness.

Selective patterning of indium tin oxide films using 1064 nm laser for micro parts processing

We report the experimental and analysis results of micro parts processing using 1064 nm Nd:YVO4 laser direct-write micro patterning of indium tin oxide (ITO) thin films and then followed by electroforming on the patterns. Compared with conventional photolithographic and etching technologies, direct-write micro-patterns of ITO using Nd:YVO4 laser at proper control can achieve high quality of surface without requiring numerous processing steps. Using diffractive multiple Nd:YVO4 beam, the ITO thin film could be removed without any damage to the glass structure. After laser patterning, a high overlapping area of laser spot was used to pattern the electrode layer on film surface for obtaining a fine ablated edge profile. Accordingly, the micro parts can be obtained using electroforming and release process via laser-patterned ITO films. The new micro parts processing is a maskless, dry and low-cost process instead of the complex photolithography, sputtering and sacrificial layer.

Fabrication of copper nanowires by eelectrodeposition uusing anodic aluminum oxide template

In this paper, effects of potential and output mode on copper nanowire arrays via porous anodic aluminum oxide template by electrochemical deposition method have been investigated. The copper nanowire arrays were fabricated using electrochemical deposition in 0.2 M CuSO4 by different potential modes including direct current (DC) and pulse. The nanostructure, morphology, chemical composition and phase of copper nanowire arrays were examined by scanning electron microscopy and grazing incidence X-ray diffraction. The results indicated that the copper nanowire arrays deposited by pulse mode revealed high aspect ratio despite high potential while that at higher DC potential was rather short due to the hydrogen generation in reduction reaction. The short duty cycle of 50% in pulse deposition can release the produced hydrogen for good nanowires formation.