Parallel Assembly Research Articles

Passive micro-assembly of modular, hot embossed, polymer microfluidic devices using exact constraint design

Low-cost microfluidic platforms have the potential to change accepted practices in many fields, including biology and medicine, in the near future. Micro-assembly of molded polymer microfluidic devices is one approach to cost-effective mass production of modular, microfluidic instruments. Polymer, passive alignment structures were used to precisely assemble molded polymer components to prevent infinitesimal motions and minimize the misalignment between assembled components and devices. The motion and constraint of the assemblies were analyzed using screw theory to identify combinations of passive alignment structures that would provide exact constraint of all degrees of freedom of the two mating parts without over-constraint. One option identified by kinematic analysis was a set of three v-groove and hemisphere-tipped pin joints, which are well known from precision engineering and suitable for microfabrication. To validate the passive alignment scheme, brass mold inserts containing alignment structures were micro-milled and used to hot emboss components in polycarbonate (PC). Dimensional and location variations of prototype alignment structures were measured to quantify the difference between the as-designed and actual dimensions and the locations of the alignment structures. The dimensional variation was 0.2–3% less than the designed dimensions and the location variation was 0.7% less. The alignment accuracy of an assembly was characterized by measuring the mismatch and vertical variation between molded alignment standards embossed on each pair of mating plates. With molded, polymer alignment structures the mean mismatch and mean vertical variation were as low as 13 ± 3 µm in the lateral plane along the x- and y-axes and −6 ± 15 µm with respect to the nominal value of 107 µm. This micro-assembly technology is applicable to the integration of all microsystems including the interconnection of microfluidic devices, the assembly of hybrid microsystems and the parallel assembly of microdevices.

Balancing and sequencing of parallel mixed-model assembly lines

In this paper, a simulated annealing approach is developed for the parallel mixed-model assembly line balancing and model sequencing (PMMAL/BS) problem which is an extension of the parallel assembly line balancing (PALB) problem introduced by Gökçen et al. (2006). In PALB, the aim is to balance more than one assembly line together. Balancing of the lines simultaneously with a common resource is very important in terms of resource minimisation. The proposed approach maximises the line efficiency and distributes the workloads smoothly across stations. The proposed approach is illustrated with two numerical examples and its performance is tested on a set of test problems. The computational results show that the proposed approach is very effective for PMMAL/BS.

Balancing parallel two-sided assembly lines

Two-sided assembly lines are usually designed to produce large-sized products such as automobiles, trucks and buses. In this type of production line, both left-side and right-side of the line are used. In parallel assembly lines, one or more product types are produced on two or more assembly lines located in parallel to each other. Both production lines have several serious practical advantages. For this purpose, in this paper, two or more two-sided assembly lines located in parallel to each other are considered and a tabu search algorithm which combines the advantages of both types of production lines is developed. To assess the effectiveness of the proposed algorithm, a set of test problems are solved. The proposed algorithm is illustrated with two examples, and some computational properties of the algorithm are given.

Distributed parallel virtual assembly environment for automobile development

PurposeAutomobile development needs more and more collaborative work involving geographical dispersed designers, that brings difficulty for model verification, conception review and assembly process evaluation, so a collaborative virtual environment for automobile based on network is required. In this kind of environment, designers can do interactive assembly operations collaboratively, such as grasp, move, release, collision detection (CD), assembly evaluation report generation, etc. Furthermore, automobile structure becomes more complicated, how to process this large real‐time data effectively in real‐time interactive virtual environment is a great challenge. The purpose of this paper is focus on this.Design/methodology/approachA distributed parallel virtual assembly environment (DPVAE) is developed. In this environment, the mechanism of event synchronization based on high‐level architecture/run‐time infrastructure) is applied to realize multi‐user collaboratively interactive operation. To meet the large data set real‐time processing demand, a creative parallel processing approach supported by a single supercomputer or a parallel processing environment composed of common personal computer in a high‐speed local area network is developed. The technologies such as real‐time CD, multiple interactive operation modals are applied in DPVAE and several auxiliary tools are provide to help achieving whole scheme review, component model verification and assembly evaluation.FindingsThis paper finds that DPVAE system is an available and efficient tool to support automobile collaborative assembly design.Practical implicationsDesigners can discuss and verify the assembly scheme to realize the previous design scenario in DPVAE, so it is useful for reducing costs, improving quality and shortening the time to market, especially for new type automobile development.Originality/valueA combination of distributed technology and parallel computing technology is applied in product virtual assembly, solving the problems including collaborative work of multi‐user and large data real‐time processing successfully, that provides a useful tool for automobile development.

Aqueous Dispersion and Dielectrophoretic Assembly of Individual Surface-Synthesized Single-Walled Carbon Nanotubes

The successful dispersion and large-scale parallel assembly of individual surface-synthesized large-diameter (1-3 nm) single-walled carbon nanotubes (SWNTs), grown by chemical vapor deposition (CVD), is demonstrated. SWNTs are removed from the growth substrate by a short, low-energy ultrasonic pulse to produce ultrapure long-term stable surfactant-stabilized solutions. Subsequent dielectrophoretic deposition bridges individual, straight, and long SWNTs between two electrodes. Electrical characterization on 223 low-resistance devices (R(average) approximately 200 kOmega) evidences the high quality of the SWNT raw material, prepared solution, and contact interface. The research reported herein provides an important framework for the large-scale industrial integration of carbon nanotube-based devices, sensors, and applications.

Experimental and theoretical study of gas/solid mass transfer in metallic filters as supports for micro-structured catalysts

Commercial sintered metallic micro-fibers have been investigated in view of their adoption as enhanced catalyst carriers. The material herein studied has high porosity (86%) and very high interfacial area (22 400 m 2/m 3), thus appearing promising for application in fast, mass-transfer limited catalytic processes. It was catalytically activated by calcination and impregnation with Pt, and tested in the model reaction of CO oxidation. The observed activity was very high: at T>500 °C, under diffusional control, CO conversions in excess of 90% were achieved at space velocities in the order of 10 6 h −1. Dimensionless mass transfer coefficients extracted from these data, accounting also for axial dispersion, exhibited. However, negative deviations from those expected either for a single infinite cylinder or from extrapolation of previous correlations for open-celled foams at higher Reynolds numbers. According to an original and unifying theoretical approach herein proposed, such deviations are quantitatively explained by accounting for the limitations to boundary layer development due to the proximity of other fibers in the densely packed system. The key point is to assume a pseudo ordered locally parallel assembly of cylinders with average distance related to the fiber diameter and to the void fraction.

Fluidic delivery of homogeneous solutions through carbon tube bundles

A wide array of technological applications requires localized high-rate delivery of dissolvedcompounds (in particular, biological ones), which can be achieved by forcing the solutionsor suspensions of such compounds through nano or microtubes and their bundledassemblies. Using a water-soluble compound, the fluorescent dye Rhodamine 610 chloride,frequently used as a model drug release compound, it is shown that deposit buildup on theinner walls of the delivery channels and its adverse consequences pose a severechallenge to implementing pressure-driven long-term fluidic delivery through nano andmicrocapillaries, even in the case of such homogeneous solutions. Pressure-drivendelivery (3–6 bar) of homogeneous dye solutions through macroscopically-long (∼1 cm) carbon nano and microtubes with inner diameters in the range 100 nm–1 µm and their bundled parallel assemblies is studied experimentally and theoretically. It isshown that the flow delivery gradually shifts from fast convection-dominated(unobstructed) to slow jammed convection, and ultimately to diffusion-limited transportthrough a porous deposit. The jamming/clogging phenomena appear to be rathergeneric: they were observed in a wide concentration range for two fluorescentdyes in carbon nano and microtubes, as well as in comparable transparent glassmicrocapillaries. The aim of the present work is to study the physics of jamming, ratherthan the chemical reasons for the affinity of dye molecules to the tube walls.

Dielectrophoretic Assembly of High-Density Arrays of Individual Graphene Devices for Rapid Screening

We establish the use of dielectrophoresis for the directed parallel assembly of individual flakes and nanoribbons of few-layer graphene into electronic devices. This is a bottom-up approach where source and drain electrodes are prefabricated and the flakes are deposited from a solution using an alternating electric field applied between the electrodes. These devices are characterized by scanning electron microscopy, atomic force microscopy, Raman spectroscopy, and electron transport measurements. They are electrically active and their current carrying capacity and subsequent failure mechanism is revealed. Akin to carbon nanotubes, we show that the dielectrophoretic deposition is self-limiting to one flake per device and is scalable to ultralarge-scale integration densities, thereby enabling the rapid screening of a large number of devices.

Metamorphic enzyme assembly in polyketide diversification

Natural product chemical diversity is fuelled by the emergence and ongoing evolution of biosynthetic pathways in secondary metabolism. However, co-evolution of enzymes for metabolic diversification is not well understood, especially at the biochemical level. Here, two parallel assemblies with an extraordinarily high sequence identity from Lyngbya majuscula form a beta-branched cyclopropane in the curacin A pathway (Cur), and a vinyl chloride group in the jamaicamide pathway (Jam). The components include a halogenase, a 3-hydroxy-3-methylglutaryl enzyme cassette for polyketide beta-branching, and an enoyl reductase domain. The halogenase from CurA, and the dehydratases (ECH(1)s), decarboxylases (ECH(2)s) and enoyl reductase domains from both Cur and Jam, were assessed biochemically to determine the mechanisms of cyclopropane and vinyl chloride formation. Unexpectedly, the polyketide beta-branching pathway was modified by introduction of a gamma-chlorination step on (S)-3-hydroxy-3-methylglutaryl mediated by Cur halogenase, a non-haem Fe(ii), alpha-ketoglutarate-dependent enzyme. In a divergent scheme, Cur ECH(2) was found to catalyse formation of the alpha,beta enoyl thioester, whereas Jam ECH(2) formed a vinyl chloride moiety by selectively generating the corresponding beta,gamma enoyl thioester of the 3-methyl-4-chloroglutaconyl decarboxylation product. Finally, the enoyl reductase domain of CurF specifically catalysed an unprecedented cyclopropanation on the chlorinated product of Cur ECH(2) instead of the canonical alpha,beta C = C saturation reaction. Thus, the combination of chlorination and polyketide beta-branching, coupled with mechanistic diversification of ECH(2) and enoyl reductase, leads to the formation of cyclopropane and vinyl chloride moieties. These results reveal a parallel interplay of evolutionary events in multienzyme systems leading to functional group diversity in secondary metabolites.

Design and analysis of digital materials for physical 3D voxel printing

PurposeVirtual voxels (3D pixels) have traditionally been used as a graphical data structure for representing 3D geometry. The purpose of this paper is to study the use of pre‐existing physical voxels as a material building‐block for layered manufacturing and present the theoretical underpinnings for a fundamentally new massively parallel additive fabrication process in which 3D matter is digital. The paper also seeks to explore the unique possibilities enabled by this paradigm.Design/methodology/approachDigital RP is a process whereby a physical 3D object is made of many digital units (voxels) arranged selectively in a 3D lattice, as opposed to analog (continuous) material commonly used in conventional rapid prototyping. The paper draws from fundamentals of 3D space‐filling shapes, large‐scale numerical simulation, and a survey of modern technology to reach conclusions on the feasibility of a fabricator for digital matter.FindingsDesign criteria and appropriate 3D voxel geometries are presented that self‐align and are suitable for rapid parallel assembly and economical manufacturing. Theory and numerical simulation predict dimensional accuracy to scale favorably as the number of voxels increases. Current technology will enable rapid parallel assembly of billions of microscale voxels.Research limitations/implicationsMany novel voxel functions could be realized in the electromechanical and microfluidic domains, enabling inexpensive prototyping of complex 3D integrated systems. The paper demonstrates the feasibility of a 3D digital fabricator, but an instantiation is out of scope and left to future work.Practical implicationsDigital manufacturing offers the possibility of desktop fabrication of perfectly repeatable, precise, multi‐material objects with microscale accuracy.Originality/valueThe paper constitutes a comprehensive review of physical voxel‐based manufacturing and presents the groundwork for an emerging new field of additive manufacturing.

High-speed, parallel DNA sequence assembly

High-speed, parallel DNA sequence assembly

The Roles of Selected Arginine and Lysine Residues of TAFI (Pro-CPU) in Its Activation to TAFIa by the Thrombin-Thrombomodulin Complex

Thrombomodulin (TM) increases the catalytic efficiency of thrombin (IIa)-mediated activation of thrombin-activable fibrinolysis inhibitor (TAFI) 1250-fold. Negatively charged residues of the C-loop of TM-EGF-like domain 3 are required for TAFI activation. Molecular models suggested several positively charged residues of TAFI with which the C-loop residues could interact. Seven TAFI mutants were constructed to determine if these residues are required for efficient TAFI activation. TAFI wild-type or mutants were activated in the presence or absence of TM and the kinetic parameters of TAFI activation were determined. When the three consecutive lysine residues in the activation peptide of TAFI were substituted with alanine (K42/43/44A), the catalytic efficiencies for TAFI activation with TM decreased 8-fold. When other positively charged surface residues of TAFI (Lys-133, Lys-211, Lys-212, Arg-220, Lys-240, or Arg-275) were mutated to alanine, the catalytic efficiencies for TAFI activation with TM decreased by 1.7-2.7-fold. All decreases were highly statistically significant. In the absence of TM, catalytic efficiencies ranged from 2.8-fold lower to 1.24-fold higher than wild-type. None of these, except the 2.8-fold lower value, was statistically significant. The average half-life of the TAFIa mutants was 8.1+/-0.6 min, and that of wild type was 8.4+/-0.3 min at 37 degrees C. Our data show that these residues are important in the activation of TAFI by IIa, especially in the presence of TM. Whether the mutated residues promote a TAFI-TM or TAFI-IIa interaction remains to be determined. In addition, these residues do not influence spontaneous inactivation of TAFIa.

ABySS: A parallel assembler for short read sequence data

Widespread adoption of massively parallel deoxyribonucleic acid (DNA) sequencing instruments has prompted the recent development of de novo short read assembly algorithms. A common shortcoming of the available tools is their inability to efficiently assemble vast amounts of data generated from large-scale sequencing projects, such as the sequencing of individual human genomes to catalog natural genetic variation. To address this limitation, we developed ABySS (Assembly By Short Sequences), a parallelized sequence assembler. As a demonstration of the capability of our software, we assembled 3.5 billion paired-end reads from the genome of an African male publicly released by Illumina, Inc. Approximately 2.76 million contigs > or =100 base pairs (bp) in length were created with an N50 size of 1499 bp, representing 68% of the reference human genome. Analysis of these contigs identified polymorphic and novel sequences not present in the human reference assembly, which were validated by alignment to alternate human assemblies and to other primate genomes.

Balancing parallel assembly lines with precise and fuzzy goals

Balancing parallel assembly lines provides flexibility to minimise the total idle times of assembly lines and the total number of workstations required in production facilities. This paper proposes two goal programming approaches to balance parallel assembly lines with precise and fuzzy goals. Three conflicting goals, namely number of workstations, cycle time, and number of tasks assigned to a workstation are optimised in crisp and fuzzy environments. The proposed approaches are also illustrated using numerical examples and sensitivity analyses. The proposed approaches provide flexibility for decision makers to balance parallel assembly lines based on their decision environments and preferred priorities.

Designing parallel assembly lines with split workplaces: Model and optimization procedure

A production system which consists of a number of parallel assembly lines is considered. On each line a certain product is manufactured observing a common cycle time. By arranging the lines in a favourable manner, it is possible to increase efficiency of the production system by combining stations of neighbouring lines when balancing them. The objective is to minimize the number of workplaces (operators) required. This problem is called parallel assembly line balancing problem (PALBP) and has previously been considered by Gökçen et al. [2006. Balancing of parallel assembly lines. Int. J. Prod. Econ. 103, 600–609]. In the paper on hand, we give a detailed problem description and model the problem as a binary linear programme. Furthermore, an exact solution approach based on an extension of the well-known branch-and-bound procedure S alome is proposed. Computational experiments show that this procedure clearly outperforms other approaches as it is able to solve small- to medium-sized problem instances to optimality and provides good heuristic solutions for large-sized problems.

Processible polyacid doped polyaniline composites: Application for charge storage devices

Processible polyaniline (PANI) composites with a polyacid (polyacrylic acid, PAA) are synthesized and studied for their structural, electrical and electrochemical properties. The material is used for the first time for development of electrochemical capacitor. The processible conducting composites have been prepared by mixing the polyaniline and polyacrylic acid in various weight percentage from 20 wt.% to 90 wt. % (of polyaniline) under vigorous stirring and sonication conditions. Self-standing films of these electroactive and homogeneous composites were obtained by solution casting method. A significant improvement in processibility, crystallinity and stability was observed in the composites having PANI up to 90 wt.% of total content. However, the electrical conductivity decreased remarkably as the percentage of PANI decreased in the composites. The composite having 60 wt.% PANI in PAA showed very interesting structural property as it is found to be highly crystalline with orthorhombic crystal system and cell parameters as a = 5.93 Å, b = 7.57 Å and c = 10.11 Å. The composites are used for the development of electrochemical capacitors. The 60 wt.% PANI-PAA composite showed highest capacitance amongst all the composites and used as an active material for development of an electrochemical capacitor using a parallel plate assembly.

Atomic scale modeling of interfacial structure of PEDOT/PSS

Theoretical calculations are performed in the framework of the interaction between the charged poly(ethylenedioxythiophene) (PEDOT 2+) and two p-toluensulfonic acid (TSA −1). The influence of the counterion on the charge distribution in the PEDOT is investigated indicating that a strong influence of the interionic correlation on the stability of PEDOT by TSA. Further several configurations are studied for the interaction between PEDOT and PSS. The calculations indicate that the side assembly is the most stable configuration, however in the presence of the solvent both parallel and side assemblies have similar stability. These results give a new insight about the charge transport conduction in PEDOT/PSS interactions.

Parallel short sequence assembly of transcriptomes

BackgroundThe de novo assembly of genomes and transcriptomes from short sequences is a challenging problem. Because of the high coverage needed to assemble short sequences as well as the overhead of modeling the assembly problem as a graph problem, the methods for short sequence assembly are often validated using data from BACs or small sized prokaryotic genomes.ResultsWe present a parallel method for transcriptome assembly from large short sequence data sets. Our solution uses a rigorous graph theoretic framework and tames the computational and space complexity using parallel computers. First, we construct a distributed bidirected graph that captures overlap information. Next, we compact all chains in this graph to determine long unique contigs using undirected parallel list ranking, a problem for which we present an algorithm. Finally, we process this compacted distributed graph to resolve unique regions that are separated by repeats, exploiting the naturally occurring coverage variations arising from differential expression.ConclusionWe demonstrate the validity of our method using a synthetic high coverage data set generated from the predicted coding regions of Zea mays. We assemble 925 million sequences consisting of 40 billion nucleotides in a few minutes on a 1024 processor Blue Gene/L. Our method is the first fully distributed method for assembling a non-hierarchical short sequence data set and can scale to large problem sizes.

Fabrication and gas sensing performance of parallel assemblies of metal oxide nanotubes supported by porous aluminum oxide membranes

We describe a conductometric chemical sensor architecture based upon an assembly of parallel metal oxide nanotubes. In this design, an aluminum oxide membrane serves as both a template for growth of the sensing nanotubes and a scaffold to support the nanotubes and the top/bottom electrical contacts for sensing measurements. Important advantages of this sensing architecture are: (1) analyte molecules are detected within the nanotube interior thereby maximizing sensitivity; and (2) metal contacts for resistance measurements are easily and reproducibly established at the ends of the nanotubes. We demonstrate a proof-of-concept for this approach by fabricating and evaluating tungsten trioxide (WO 3) nanotube-based conductometric devices. Nanotubes are formed in membrane pores (diameter ≈200 nm, length ≈60 μm) by sol–gel deposition and characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Thin film Au contacts are deposited on the top/bottom of the WO 3-coated membranes such that the tube-ends remain open, enabling conductometric sensing along the length of the WO 3 nanotubes. The nanotube assemblies detect oxidizing (nitrogen dioxide) and reducing (methanol) gases at 200 °C, and exhibit responses two to three orders-of-magnitude greater than a planar WO 3-film sensor. The enhanced sensitivity is attributed to the large surface area presented by the interior of the nanotube assemblies.

A High Performance Multifrontal Code for Linear Solution of Structures Using Multi-Core Microprocessors

A multifrontal code is introduced for the efficient solution of the linear system of equations arising from the analysis of structures. The factorization phase is reduced into a series of interleaved element assembly and dense matrix operations for which the BLAS3 kernels are used. A similar approach is generalized for the forward and back substitution phases for the efficient solution of structures having multiple load conditions. The program performs all assembly and solution steps in parallel. Examples are presented which demonstrate the code's performance on single and dual core processor computers.