No abstract

A microchip has been developed on the basis of immno-precipitation approach for fast and sensitive enrichment of low abundant carbonylated proteins. This microfluidic method could enrich molecular biomarkers, which could be further analyzed in the proteomic study of age-related diseases and therapeutic development. In this study, an immunoaffinity-based PDMS micro-device was designed, fabricated, and chemically modified to specifically trap DNP-labeled PTM proteins of low abundance from a complex protein mixture. Carbonylated protein is selected as a representative PTM protein to illustrate the wide application of this immuno-based microchip for other PTMs which could be readily labeled by different antibody groups. Surface characterization methods such as atomic force microscopy and fluorescence microscopy were used to evaluate the construction of glutaraldehyde- and antibody- terminated PDMS substrates in the device fabrication. Quantitative study was also applied to study the target protein capture and elution efficiency of the device. In a testing mixture consisting of smaller amount of test model-In Vitro oxidized cytochrome c and large blocking protein BSA, a high sensitivity and specificity for only carbonylated protein biomarkers was demonstrated using this on-chip immnuoaffinity based extraction/enrichment. For this highly dense 193-post arrays μ-chip, a low abundance of 159 ng of standard in vitro test model- cytochrome c was enriched at flow speed of 5 μL/min within 110 min. We demonstrated that this nascent micro-immunoprecipitation (μ-IP) method is capable for enrichment of biomarkers in protein post-translation modification related diseases and promise great advance in early disease detection.

Giant magneto resistance (GMR)-based microfluidic biosensors are used in applications involving the detection, analysis, enumeration and characterization of magnetic nano-particles attached to biological mediums such as antibodies and DNA. Here we introduce a novel multilayered CoNiCu/Cu nanowire GMR-based microfluidic biosensor. The current perpendicular to the plane of multilayers (CPP)-nanowires GMR was used as the core sensing material in the biosensor which responds to magnetic fields depending on the concentration and the flow velocity of bio-nano-magnetic fluids. The device was tested with different control solutions such as DI-water, mineral oil, phosphate buffered saline (PBS), ferrofluid, polystyrene superparamagnetic beads (PSB) and Dynabeads sheep anti-rabbit IgG. The nanowire array resistance decreased with an increase in the ferrofluid concentration, and a maximum 15.8% relative GMR was observed for the undiluted ferrofluid. The sensor was also responding differently to various ferrofluid flow rates. The GMR device showed variation in the output signal when the PSB and Dynabeads of different dilutions were pumped through it. When the tests were performed with pulsing potentials (150 mV and 200 mV), an increased GMR response was identified at higher voltages for PSB and Dynabeads sheep anti-rabbit IgG.

The need for dissipating heat from microsystems has increased drastically in the last decade. Several methods of heat dissipation using air and liquids have been proposed by many studies, and pin-fin micro heat sinks are one among them. Researchers have developed several effective pin-fin structures for use in heat sinks, but not much effort has been taken towards the optimization of profile and dimensions of the pin-fin. In this paper the authors studied the effect of different pin-fin shapes on the thermal resistance and pressure drop in a specific micro heat-sink. Optimization subjected to two different constraints is studied in this paper. The first optimization is subjected to constant flow rate and the second one is subjected to constant pressure drop. Both optimization processes are carried out using computer simulations generated using COVENTORWARE™. Two of the best structures from each of these optimization studies are selected and further analysis is performed for optimizing their structure dimensions such as width, height and length. A section of the total micro heat-sink is modeled for the initial optimization of the pin-fin shape. The model consists of two sections, the substrate and the fluid. Six different shapes: square, circle, rectangle, triangle, oval and rhombus were analyzed in the initial optimization study. Preliminary tests were conducted using the first model described above for a flow rate of 0.6ml/min. The non dimensional overall thermal resistance of the heat sink, and the nondimensional pumping power was calculated from the results. A figure of merit (FOM) was developed using the nondimensional thermal resistance and nondimensional pumping power for each structure with different pin-fin shapes. Smaller the value of FOM better the performance of the heat sink. The study revealed that the circle and ellipse structures have the best performance and the rectangle structure had the worst performance at low flow rates. At high flow rates rectangular and square structures have the best performance.

The effect of channel width and channel spacing on the flow distribution in a microfluidic device with U-type manifolds is numerically analyzed in this paper. Analysis is performed for flow rates between 1 ml/min and 60 ml/min. Flow distribution in a microfluidic device with three different microchannel widths are studied: 50 μm, 100 μm, and 200 μm. Reduction in the microchannel width reduced the non-uniformity in flow rate. Moreover, the flow malidistribution increased with increase in flow rate. The RMS value of the deviation of flow rate per channel reduced from 3 ml/min to 0.3 ml/min with reduction in channel width for a total flow rate of 60 ml/min. The effect of channel spacing on flow distribution was investigated for three channel spacing of 300 μm, 100 μm, and 50 μm. Reduction in channel spacing increased nonuniformity of flow distribution. The RMS value of the deviation of flow rate per flow rate reduced from 1 ml/min to 0.6 ml/min with increase in channel spacing for the greatest flow rate. From the particular studies examined in this paper it is found channel width has a stronger influence on flow distribution than channel spacing. Moreover, proper selection of channel width and channel spacing can uniformly distribute flow.