µTransparent insulating channels as components for miniaturized chemical separation Devices

Currently, miniaturized devices that apply electro osmotic pumping or electrophoretic separations are mostly constructed by etching small insulating channels for supply and separation on glass substrates. In principle, silicon is a superior construction material in terms of inertness and design flexibility. However, because of its semiconducting properties, the use in high voltage applications like the ones mentioned above is quite limited. In this paper, the use of μTransparent Insulating Channel (μTIC) technology is demonstrated as a standard procedure to manufacture miniaturized analytical separation devices. This technique, μchannels having extremely thin, transparent and insulating walls can be fabricated. An overview of the impact of this technology is given, showing the advantages of a fabrication technology that is as flexible as silicon technology for the fabrication of μTAS or “lab on a chip” devices. The following basic technology and control parameters will be highlighted. 1. Up to 100 μm wide rectangular channels 2. Bosses and leak-free connections to external μ fluidics. 3. Web-like structures for inlets/outlets>100 μm. 4. Implementation of conductivity electrodes 5. Good thermal dissipation properties of the thin walls 6. Control of the electro osmotic flow by a radial voltage

A new approach to immunoFET operation

A new method is presented for the detection of an immunological reaction taking place in a membrane, which covers the gate area of an ISFET. By stepwise changing the electrolyte concentration of the sample solution, a transient diffusion of ions through the membrane-protein layer occurs, resulting in a transient membrane potential, which is measured by the ISFET. The diffusion rate is determined by the immobile charge density in the amphoteric protein layer, which changes upon formation of antibody—antigen complexes. No membrane potential is induced at zero fixed charge density as occurs at a protein characteristic pH. Isoeletric points of embedded proteins can be determined by detecting the zero potential response.\ud \ud Up to now, the authors have studied the membrane adsorption of lysozyme, human serum albumin (HSA) and the immune reaction of HSA with the antibody anti-human serum albumin (αHSA). The influence of protein parameters on the amplitude of the transient can be described with an empirical equation. Assuming Langmuir behaviour, the protein concentration in the solution can well be correlated with the concentration in the membrane.\ud \ud This new detection method is unique concerning direct measurements of charge densities and isoelectric points of amphoteric macromolecules adsorbed in the membrane. The simple procedure of one incubation stage followed by one detection stage, without separate washing and labelling techniques, gives direct information about specific charge properties of the macromolecules to be studied

Laminar Flow Microarray Patterning by Perpendicular Electrokinetic Focusing

This paper describes a method to pattern microarrays in a closed microfluidic device. Two perpendicular laminar flow streams can operate in terms to sequentially coat the surface of a flow-chamber with parallel lanes in two directions. Two perpendicular sample streams can be controlled in position and width by applying electrokinetic focusing, for which each of the two streams is sandwiched between two parallel laminar flow streams containing just a buffer solution. Electroosmotic flow allows a simple chip design without any moving parts being involved. With this device configuration it is possible to define an array of up to 169 spots on a surface area of 1 mm2

Combined Lab-on-a-Chip and microarray approach for biomolecular interaction sensing using surface plasmon resonance imaging

Surface plasmon resonance imaging (SPR) is a well-established label-free detection technique for real-time biomolecular interaction measurements. An integrated LOC sensing system with fluidic control for sample movement to specific locations on microarray surface in combination with SPR imaging is demonstrated by the measurements of human IgG and anti-IgG interactions from 24 patterned regions.\u