[en] In this paper, a very simple top-down fabrication method, which is compatible with standard silicon (Si) fabrication processes, is proposed to fabricate new suspended gold nanowire bridges with flexible designs. The electrical characteristics of the nanowire bridges which include the V–I curve, thermoresistive and impedance spectra change before and after nanowire bridges release and resistivity change with different design parameters are measured. The suspended nanowire bridge structures show the reduction of interference from the substrate and a large design flexibility to fit varying application desires. Furthermore, the nanowire bridge has shown a high potential for biomolecular detection by the mechanical, electrical or optical sensing mechanism through the formation of functionalized self-assembled monolayers (SAMs) on the bridge structure

[en] This work presents the design, fabrication and characterization of a modular magnetic bead-based cell separation device developed for the sequential sorting of a heterogeneous prostate cancer (CaP) cell population. The chief aim is cell sorting carried out on the basis of surface marker expression, serially selecting cellular subpopulations for capture by the use of antibody-coated magnetic beads. The markers of interest, prostate specific membrane antigen (PSMA) and CD10 were selected for their relevance to ongoing CaP development research. The separation device was fabricated out of plastic, by the use of cyclic olefin copolymer (COC) injection molding, nickel–iron electroplating and thermoplastic fusion bonding. Effective depletion and enrichment of cell subsets based on multiple surface markers was achieved. Various flow rates and incubation times were tested for optimizing the sorting procedure

[en] As a result of increased water demand and water pollution, both surface water and groundwater quantity and quality are of major concern worldwide. In particular, the presence of nutrients and heavy metals in water is a serious threat to human health. The initial step for the effective management of surface waters and groundwater requires regular, continuous monitoring of water quality in terms of contaminant distribution and source identification. Because of this, there is a need for screening and monitoring measurements of these compounds at contaminated areas. However, traditional monitoring techniques are typically still based on laboratory analyses of representative field-collected samples; this necessitates considerable effort and expense, and the sample may change before analysis. Furthermore, currently available equipment is so large that it cannot usually be made portable. Alternatively, lab chip and electrochemical sensing-based portable monitoring systems appear well suited to complement standard analytical methods for a number of environmental monitoring applications. In addition, this type of portable system could save tremendous amounts of time, reagent, and sample if it is installed at contaminated sites such as Superfund sites (the USA's worst toxic waste sites) and Resource Conservation and Recovery Act (RCRA) facilities or in rivers and lakes. Accordingly, state-of-the-art monitoring equipment is necessary for accurate assessments of water quality. This article reviews details on our development of these lab-on-a-chip (LOC) sensors. (topical review)

[en] A new dead-volume-free PDMS pinch microvalve has been designed, fabricated and characterized in this work for valving and flow regulation on rigid polymer lab chips as an embedded modular platform. The pinch microvalve is operated by compressing a microfabricated flexible channel with an external actuation force. The assembly of modular PDMS pinch microvalves within rigid thermoplastic microfluidic devices provides numerous benefits in realizing hybrid polymer lab chips with functionality to precisely regulate flow. Flow rates of the developed pinch microvalve were characterized with respect to the pinch valve channel dimension and the pinching displacement distance applied to the valve. Finally, a microfluidic system with a single channel that branches into four pinch-valved channels was realized and a novel scheme for simultaneously actuating all four valves with a single actuator was demonstrated. The microfluidic PDMS pinch valves developed in this work will have a variety of applications in microfluidic systems developed in rigid polymers

[en] The rapid progress of droplet microfluidics and its wide range of applications have created a high demand for the mass fabrication of low-cost, high throughput droplet generator chips aiding both biomedical research and commercial usage. Existing polymer or glass based droplet generators have failed to successfully meet this demand which generates the need for the development of an alternate prototyping technique. This work reports the design, fabrication and characterization of a mass manufacturable thermoplastic based microfluidic droplet generator on cyclic olefin copolymer (COC). COC chips with feature size as low as 20 µm have been efficiently fabricated using injection molding technology leading to a high production of inexpensive droplet generators. The novelty of this work lies in reoptimising surface treatment and solvent bonding methods to produce closed COC microchannels with sufficiently hydrophobic (contact angle of 120°) surfaces. These COC based droplet generators were shown to generate stable monodisperse droplets at a rate of 1300 droplets/second in the dripping regime. These new mass manufacturable, disposable and cheap COC droplet generators can be custom designed to cater to the rapidly increasing biomedical and clinical applications of droplet microfluidics. (paper)

[en] A low-cost nano-gap interdigitated electrode array (IDA) on a polymer substrate has been developed to realize a disposable nano-biosensor for biochemical clinical analysis. Utilizing the common instruments for optical lithography, nano-scale features were fabricated on a thermoplastic polymer to produce an electrochemical nano-biosensor in a disposable format. The IDA was realized on a 3-inch cyclo-olefin copolymer wafer, which illustrates the utility of our fabrication technique as a large-area nanofabrication process for a polymer using low temperature processes. In order to demonstrate the use of the sensor for lab-on-a-chip applications, the developed IDA was integrated with a microfluidic channel and applied for the electrochemical detection of poly-aminophenol with 10"−"8 M detection limit. The results indicate the developed fabrication technique is suitable for the inexpensive mass fabrication of highly sensitive nano-biosensors for disposable applications. (paper)

[en] A new method for the self-assembly of a carbon nanotube (CNT) using magnetic capturing and fluidic alignment has been developed and characterized in this work. In this new method, the residual iron (Fe) catalyst positioned at one end of the CNT was utilized as a self-assembly driver to attract and position the CNT, while the assembled CNT was aligned by the shear force induced from the fluid flow through the assembly channel. The self-assembly procedures were successfully developed and the electrical properties of the assembled multi-walled carbon nanotube (MWNT) and single-walled carbon nanotube (SWNT) were fully characterized. The new assembly method developed in this work shows its feasibility for the precise self-assembly of parallel CNTs for electronic devices and nanobiosensors.

[en] Highlights: • Detailed numerical analysis of thermoelectric module for radiant heat recovery. • Case study on radiant heat recovery in hot steel casting process. • Radiation heat exchanges and parasitic heat losses taken into account. • Module design optimization in terms of power density, efficiency, and power cost. - Abstract: We present a detailed numerical analysis to quantify the power generation performance of a thermoelectric module in radiant heat recovery application. Due to the large temperature difference typically involved in such a system, temperature-dependent material properties of thermoelectric elements are taken into account for accurate performance prediction by employing an iterative algorithm based on the one-dimensional finite element method. Careful analysis on the radiation heat transfer with optical parameters such as surface emissivity and view factor is performed to precisely quantify the heat input to the thermoelectric system. Parasitic heat losses such as air convection loss at the hot surface and conduction through the substrates and gap fillers are also taken into account to analyze their impacts on the power output. A case study on the radiant waste heat recovery from hot steel casting slabs in steel industry is discussed in detail to theoretically estimate the power output performances and optimize the module design. We find that a power density as high as ∼1.5 kW/m² and a system efficiency as high as ∼4.6% can be achieved at a 2 m distance from the 1200 K hot steel slab using the state-of-the-art Bi₂Te₃ alloys with a relatively small leg thickness of 3 mm and a 20% fill factor. This optimal design with small form factors ensures a reduced material cost while keeping the power output near the maximum, so that an estimated power cost remains as low as ∼0.2 $/Watt.