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Protein microarrays are emerging as an important enabling technology for the simultaneous investigation of complicated interactions among thousands of proteins. The solution-based blocking protocols commonly used in protein microarray assays often cause cross-contamination among probes and diminution of protein binding efficiency because of the spreading of blocking solution and the obstruction formed by the blocking molecules. In this paper, an alternative blocking process for protein microarray assays is proposed to obtain better performance by employing a vapor-phase deposition method to form self-assembled surface coatings using a highly fluorinated organosilane as the blocking agent on the background surfaces. Compared to conventional solution-based blocking processes, our experimental results showed that this vapor-phase process could shorten the blocking time from hours to less than 10 min, enhance the binding efficiency by up to 6 times, reduce the background noise by up to 16 times, and improve the S/N ratio by up to 64 times. This facile blocking process is compatible with current microarray assays using silica-based substrates and can be performed on many types of silane-modified surfaces.

Conventional pick-and-place technology platform in handling microscale component assembly processes has technical limitations in terms of capacity, efficiency, and accuracy. The fluidic self-assembly (FSA) approach employs a lubricant fluid carrying micropart flows over a target wafer patterned with binding sites, which results in part-substrate attachment. This technique transports microparts from one location to another with orientation control and parallel sorting. The present study demonstrates a FSA approach for fast, economic, and precise handling of microscale parts with square (few are in rectangular) shapes. The microparts fabricated from silicon-oxide wafers and ranging in size from 350 x 350 x 170 [micro][m.sup.3] to 1000 x 1000 [micro][m.sup.3] aligned and filled to designated sites in the substrate under water. The effects of micropart sizes and lubricants on the FSA processes are compared. This study provides a fundamental analysis for achieving and optimizing the self-alignment. The polymer or solder adhesion force of the square-patterned micropart immobilized at the larger binding sites were estimated to be 117 [+ or -] 15 [micro]N and 510 [+ or -] 50 [micro]N, respectively, which results in higher assembly yield of up to 100% for these samples. [DOI: 10.1115/1.2912216] Keywords: fluidic self-assembly (FSA), self-assembled monolayer (SAM), micropart, lubricant

This paper develops a novel microcontact printing system for printing tens of protein solutions into an array with batch filling and parallel printing. This printing system consists of microfilling and microstamp chips. The microfilling chip can simultaneously transfer numerous protein solutions into the microstamp chip in seconds by capillary force without cross contamination while preserving the functionality of proteins. Different proteins can be dispensed into the corresponding channels and driven into the tips of the microstamps. The microstamp can then be brought to contact with the substrate to produce biofluid spot arrays. Teflon patterns are applied on both microfilling and microstamp chips to prevent cross contamination during filling. Thirty-six proteins can be printed in parallel with a spot size variation of less than 5%. This device has a potential to be expanded to a passive and high-throughput system for simultaneously printing hundreds of biofluid spots to form dense arrays for diagnosing disease or screening for drugs. [2007-0083] Index Terms--Microcontact printing, protein microarray.

There have been many microdeposition processes that are based on the evaporation of nanoliter-sized droplets, such as inkjet printing, deoxyribonucleic acid/protein microarrays, or lithography direct writing. However, it is important but still difficult to control the uniformity of the solute deposition from a nanoliter sessile droplet on a plane substrate. This paper proposes a method for uniform solute deposition from evaporable droplet by confining the droplet with rib structures (wells) of specific surface properties. The hydrodynamic process was experimentally investigated and analyzed in detail. Surface wett-ability on the well surface is verified to be critical for controlling a droplet as a flat film inside a well during evaporation to minimize horizontal solute transfer for uniform solute deposition. Pure water and water/tracing particle mixture (2.57% solid latex, dyed blue) were employed for the test. The results demonstrated that a 97% uniformity is obtained for the solute deposited from a 37-nL droplet in a well with hydrophobic surface (contact angle of 100[degrees]), whereas a 31% uniformity is obtained for a more hydrophilic surface (contact angle of 25[degrees]). The higher hydrophobicity (contact angle above 90[degrees]) on the well surface yields a flatter profile of film during droplet evaporation inside a well and, thus, promotes a more uniform deposition of the solute. [2006-0194] Index Terms--Evaporation, microdroplet, microwell, solute deposition.

Bubble dynamics of explosive microthermal dual bubbles including the growth and collapse process are investigated experimentally in detail. The dual bubbles are generated with supplied heat flux of 1.61 GW/[m.sup.2] on two 30 x 60 [micro][m.sup.2] heaters. The heaters are separated by different distances ranging from 25 to 125 [micro]m. As the heaters get closer in x-direction, higher anisotropic degree in directional extensions of dual bubbles is obtained with faster bubble expansion velocity during collapse in x-, y-, and z-directions. In addition, the bubble lifetime is shorter as the two heaters are separated more although the supplied heat flux is the same. Furthermore, one application of dual bubble system actuating the droplet formation demonstrates that the droplet formation process with no satellites can be achieved by adjusting the expansion rate of bubbles or the spacing between two heaters. [1627] Index Terms--Bubble-bubble Interactions, droplet injection, flow visualization, numerical simulation, thermal microbubble.

This paper proposes a novel passive micromixer design for mixing enhancement by forming a large three-dimensional (3-D) flow vortex in a counterflow microfluidic system. The counterflow fluids are self-driven by surface tension to perform mixing in an open chamber. The chamber design consists of two rectangular bars to house the chamber and to form two opening inlets from opposite directions. The best design is selected from various versions of mixing chambers. The mixing effectiveness is tremendously increased by folds of contacting surface between two fluids induced and enhanced due to the stretching of two fluid contacting interfaces by the formation of a 3-D large size vortex structure inside the mixing chamber itself with unaccountable numbers of fluid layers. Both numerical simulations and experiments are performed and compared to identify the design parameters for maximum utilization in this microfluidic system, such as the length of rectangular bar, microchannel wall height, and mixing chamber size. Compared to traditional micromixers operated by two-dimensional (2-D) vortex, this passive mixer can greatly enhance mixing efficiency and reduce mixing time by tenfold from around 10 s to less than 10 ms by 3-D effective chaotic flow structures in a more compact size. This mixing chamber is also suitable for an H-shape digital fluidic system for parallel mixing process in different mixing ratio simultaneously as a lab-on-a-chip system. [1509] Index Terms--Microfluidics, mixing, surface tension, vortex.

A study was conducted to analyze the application of the biconjugate conjugate gradient stable method relaxation technique to the compressible Navier-Stokes solver with the Baldwin-Barth one-equation model of turbulence. Results indicated the efficiency of the relaxation method. It was characterized by a fast convergence behavior wen the multigrid and implicit algorithm were simultaneously implemented.

The variants of preconditioned biconjugate gradient methods used in the compressible Navier-Stokes solver with the k-epsilon two-equation model for transonic separated flows shows that a fast convergence rate can be attained by the preconditioned variants and the residuals can be further decreased as the iterations are continued. This indicates that the computation of the turbulent flow with a two-equation model is possible within a reasonable computer time and with high accuracy.

Optical absorption and thermal conduction are the two key factors affecting temperature distribution and, subsequently, the write, erase characteristics of a phase-change optical recording disk. Therefore, by using carefully measured film physical properties of each layer, this work simulates a transient temperature profile while simultaneously considering optical absorption and thermal conduction. Through the simulated transient temperature profile, cooling-rate and reflectivity, dependence of phase-changed spot size on the laser power and laser pulse duration was observed. The proper combination of the disk structure and the associated write, erase conditions are obtained as well. A disk structure can subsequently be designed on the basis of this information. in addition, a novel dielectric layer, i.e. hydrogenated amorphous carbon ([Alpha]-C:H), is simulated and compared with the disk applying conventionally used ZnS-Si[O.sub.2] dielectric layers. The disk structures used herein are PC/ZnS-Si[O.sub.2]/GeSbTe/ZnS-Si[O.sub.2]/Al and PC/[Alpha]-C:H/GeSbTe/[Alpha]-C:H/Al. According to those results, [Alpha]-C:H film is highly promising as a dielectric layer of the phase change optical recording disk for both wavelengths of 780 and 660 nm.

Dynamic information, such as force, structural change, interaction energy, and potential of mean force (PMF), about the desorption of a single cardiotoxin (CTX) protein from a methyl-terminated self-assembled monolayer (SAM) surface was investigated by means of steered molecular dynamics (SMD) simulations. The simulation results indicated that Loop I is the first loop to depart from the SAM surface, which is in good agreement with the results of the nuclear magnetic resonance spectroscopy experiment. The free energy landscape and the thermodynamic force of the CTX desorption process was represented by the PMF and by the derivative of PMF with respect to distance, respectively. By applying Jarzynski's equality, the PMF can be reconstructed from the SMD simulation. The PMFs, calculated by different estimators based upon Jarzynski's equality, were compared with the conventional umbrella sampling method. The best estimation was obtained by using the fluctuation-dissipation estimator with a pulling velocity of v = 0.25 nm/ns for the present study. [ABSTRACT FROM AUTHOR]

This study aims to construct a force interaction model for thermal conductivity computation and to analyze the liquid properties in atomic level for liquid ethylene glycol (EG) using molecular dynamic simulation. The microscopic details of the molecular system and the macroscopic properties of experimental interest are connected by Green-Kubo relations. In addition, the major contributions of heat transfer modes for thermal conductivity due to convection, interaction, and torque are obtained quantitatively. This study reveals that the intramolecular interaction force fields result in different conformations of the EG in the liquid and thus the molecular shapes. The trans/gauche ratio for EG's O-Me-Me-O torsional angle and the number of intermolecular/intramolecular H-bonds are found to be important parameters affecting the thermal conductivity. [ABSTRACT FROM AUTHOR]