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This work describes the development of a miniaturized potentiometric system comprising a miniaturized quasi‐reference electrode (QRE) coupled to a solid‐state ion‐selective electrode (ISE) for the monitoring of pH. We describe the optimization of materials and fabrication processes including screen‐printing (SP), electrode treatments (thermal and electrochemical) and the formulation and deposition of an ion‐selective membrane (ISM), to obtain a system compliant with biomedical specifications. We developed a potentiometric system composed of an Ag/AgCl QRE and a pH‐electrode (ISM deposited on a graphite electrode) that can be used continuously for a period of not less than 7 days in aqueous solutions. Curing the Ag/AgCl pastes during 20 minutes at 120 °C after printing allowed the QREs to display excellent potential stability, as demonstrated by an open‐circuit‐potential standard deviation of ±1.2 mV over a period of 7 days (n=3 samples). Promoting adhesion of the pH membrane over graphite electrodes improved the pH‐electrode performance. This was achieved through a combination of thermal treatment and electrochemical activation of the electrodes by cyclic voltammetry (CV). The final device integrated both the QRE and the pH‐electrode, and displayed an average pH sensitivity of −60.8±1.7 mV per pH unit, over a pH range of 7.00 to 7.63.

We propose a polymer-based microfluidic motherboard that integrates waveguides and fluidic networks providing an interface between microfluidic systems and the outer world. The motherboard facilitates interconnections of several microfluidic chips for multiplexed and simultaneous analysis. It offers a modular network for microfluidic chips, allowing complex microfluidic processes, where each microchip has a particular function. The motherboard includes microfluidic channels machined by micromilling technology and bonded thermally. Waveguides were integrated in the motherboard in the same fabrication process. Additionally, pins were fabricated, which are part of the fluidic interconnections and allow the alignment of a chip with the waveguides of the motherboard. To establish high density microfluidic interconnections between the motherboard and external tubes, reversible PDMS sockets have been utilized. For interconnecting the polymer waveguides to the light source and to the detection system, PDMS optical plugs have been developed. To demonstrate the performance of the device, test structures were designed that contained fluidic channels, waveguides and, additionally, custom made o-rings allowing alignment to the connection pins of the motherboard. The single chips were attached to the motherboard by just pressing them onto the alignment pins. A sealed fluidic connection between chip and motherboard is ensured by the deliberate mismatch in diameter between the o-rings of the chip and the pins of the motherboard. The maximally applicable hydraulic pressure before leakage, as well as propagation and coupling losses for the waveguides and optical interconnections have been characterized and tested.

As a step toward high-throughput bioprocess development, we present design, fabrication, and characterization of polymer based microbioreactors integrated with automated sensors and actuators. The devices are realized, in increasing levels of complexity, in poly(dimethylsiloxane) and poly(methyl methacrylate) by micromachining and multilayer thermal compression bonding procedures. Online optical measurements for optical density, pH, and dissolved oxygen are integrated. Active mixing is made possible by a miniature magnetic stir bar. Plug-in-and-flow microfluidic connectors and fabricated polymer micro-optical lenses/connectors are integrated in the microbioreactors for fast set up and easy operation. Application examples demonstrate the feasibility of culturing microbial cells, specifically Escherichia coli, in 150 μL-volume bioreactors in batch, continuous, and fed-batch operations. (JALA 2007;12:143–51)

As a step toward high-throughput bioprocess development, we present design, fabrication, and characterization of polymer based microbioreactors integrated with automated sensors and actuators. The devices are realized, in increasing levels of complexity, in poly(dimethylsiloxane) and poly(methyl methacrylate) by micromachining and multilayer thermal compression bonding procedures. Online optical measurements for optical density, pH, and dissolved oxygen are integrated. Active mixing is made possible by a miniature magnetic stir bar. Plug-in-and-flow microfluidic connectors and fabricated polymer micro-optical lenses/connectors are integrated in the microbioreactors for fast set up and easy operation. Application examples demonstrate the feasibility of culturing microbial cells, specifically Escherichia coli, in 150 μL-volume bioreactors in batch, continuous, and fed-batch operations. (JALA 2007;12:143–51)

This study presents a novel method for rapid prototyping of polymer microsystems. The method is based on excimer laser ablation of a thermally and mechanically stable polymer, such as PEEK (poly-ether-ether-ketone). A negative of the desired microsystem is laser machined in PEEK, which can then be used directly for hot embossing or injection moulding of a series of prototypes. This approach is very rapid and considerably cheaper than more traditional approaches to toolmaking, while still performing well in terms of reproduction of tool dimensions. The reduction in time and cost for a master tool using this method opens up new possibilities for testing small series in the R&D phase of a microsystem. Finally, two particular applications of the technique are presented.

This study presents a novel method for rapid prototyping of polymer microsystems. The method is based on excimer laser ablation of a thermally and mechanically stable polymer, such as PEEK poly-ether-ether-ketone. A negative of the desired microsystem is laser machined in PEEK, which can then be used directly for hot embossing or injection moulding of a series of prototypes. This approach is very rapid and considerably cheaper than more traditional approaches to toolmaking, while still performing well in terms of reproduction of tool dimensions. The reduction in time and cost for a master tool using this method opens up new possibilities for testing small series in the R&D phase of a microsystem. Finally, two particular applications of the technique are presented.

A hybrid multiplex microarray microsystem has been developed that consists of 32 individually addressable array reaction chambers, supporting the use of multichannel pipettes for addition of up to 8 samples simultaneously. Discrimination between Campylobacter jejuniand Campylobacter colibacteria was observed in DNA samples containing Campylobacterspp., with the same specificity and sensitivity as when compared to a full-size microarray. The spinloaded multiplex microarray microsystem described provides a novel and convenient test format for simultaneous low-density microarray analysis and is universally adaptable to other DNA, protein or small molecule microarray based applications.

In this paper we describe the use of a CO2laser for production of cavities and microstructures in poly(methyl methacrylate) PMMA by moving the laser beam over the PMMA surface in a raster pattern. The topography of the cavities thus produced is studied using stylus and optical profilometry and scanning electron microscopy SEM. The microstructures display artifacts from the laser ablation process and we describe how the laser ablation parameters can be optimized in order to minimize these artifacts. Using this technique it is possible to generate structures with a depth from 50 µm and a minimum width of approximately 200 µm up to depth and widths of several mm, governed by the beam size and the laser settings.

A hybrid multiplex microarray microsystem has been developed that consists of 32 individually addressable array reaction chambers, supporting the use of multichannel pipettes for addition of up to 8 samples simultaneously. Discrimination between Campylobacter jejuni and Campylobacter coli bacteria was observed in DNA samples containing Campylobacter spp., with the same specificity and sensitivity as when compared to a full-size microarray. The spinloaded multiplex microarray microsystem described provides a novel and convenient test format for simultaneous low-density microarray analysis and is universally adaptable to other DNA, protein or small molecule microarray based applications.

In this article, we focus on the enormous potential of a CO₂-laser system for rapidly producing polymer microfluidic structures. The dependence was assessed of the depth and width of laser-cut channels on the laser beam power and on the number of passes of the beam along the same channel. In the experiments the laser beam power was varied between 0 and 40 W and the passes were varied in the range of 1 to 7 times. Typical channel depths were between 100 and 300 μm, while the channels were typically 250 μm wide. The narrowest produced channel was 85 μm wide. Several bonding methods for microstructured PMMA [poly(methyl methacrylate)] parts were investigated, such as solvent-assisted glueing, melting, laminating and surface activation using a plasma asher. A solvent-assisted thermal bonding method proved to be the most time-efficient one. Using laser micromachining together with bonding, a three-layer polymer microstructure with included optical fibers was fabricated within two days. The use of CO₂-laser systems to produce microfluidic systems has not been published before. These systems provide a cost effective alternative to UV-laser systems and they are especially useful in microfluidic prototyping due to the very short cycle time of production.

A simple colorimetric technique is implemented in a polymer microfluidic manifold. The simple chemistry aids an uncomplicated microchannel design, which is fabricated by CO2laser ablation. Issues such as bonding of multiple layers, alignment of micro-fabricated structures and integration of optical components are addressed. A demonstration of a stopped flow regime in the microfluidic manifold is also presented.

For Abstract see ChemInform Abstract in Full Text.