Arash Dodge

X-ray microfocussing combined with microfluidics for on-chip X-ray scattering measurements

This work describes the fabrication of thin microfluidic devices in Kapton (polyimide). These chips are well-suited to perform X-ray scattering experiments using intense microfocussed beams, as Kapton is both relatively resistant to the high intensities generated by a synchrotron, and almost transparent to X-rays. We show networks of microchannels obtained using laser ablation of Kapton films, and we also present a simple way to perform fusion bonding between two Kapton films. The possibilities offered using such devices are illustrated with X-ray scattering experiments. These experiments demonstrate that structural measurements in the 1 A-20 nm range can be obtained with spatial resolutions of a few microns in a microchannel.

Consequences of opposing electrokinetically and pressure-induced flows in microchannels of varying geometries

This work confirms experimentally the linear dependence of electro-osmotic velocity on an imposed hydrostatic counter pressure. The effect of hydrostatic pressure-induced flow (PH) becomes significant on electroosmotic flow (EOF) in microchannels with increasing hydraulic diameter (Dh). A detailed investigation of flow streamlines when EOF and PH coexist in opposing directions was carried out, using both simulation tools and microspheres to visualize flows. It was shown that bi-directional flow can be generated. Furthermore, numerical calculations partially explain formation of circulating microsphere clusters at the expansion of narrow channels.

Combined Nucleic Acid Extraction and Enrichment in Bead-packed Plastic Beds

Sample pre-treatment and DNA analysis are recent trends in microfluidics. In this paper, we describe nucleic acid extraction from a poly(dimethylsiloxane) (PDMS) channel packed with silica beads. The extraction of nucleic acids from biological samples such as Human Papilloma Virus (HPV) and human cell lysates were successful, with the collection of the nucleic acids in the first 10 μL of eluate. The integration of platinum electrodes just below the packing is being explored as way to reversibly collect the eluted nucleic acids and preconcentrate them on-chip.

Valveless, sealed microfluidic device for automated heterogeneous immunoassay: design and operational considerations

Improved turnaround of immunodiagnostic tests will rely on more flexible, automated instrumentation which could be used away from a centralized clinical laboratory. This paper will examine an integrated microsystem-based platform for rapid heterogeneous immunoassay. Efforts to automate operation of this system and characterize its chemical aspects are described. It was possible to perform immobilized Protein A/rIgG binding assays in less than 2 minutes.

Integrated Temperature Control System for Microfluidic Devices

for localized temperature control in microfluidic devices, integrated cooling and heating systems are required. To date, several heating systems for microfluidic devices have been presented based on resistive heating. However, no integrated cooling systems have been reported yet. Here, a microfluidic cooling and heating system based on endothermic and exothermic reactions is presented.

A Microfluidic Chip for Multi-Step, Heterogeneous Immunological Reactions

In previous work, we demonstrated a simple heterogeneous immunoreaction in a microfluidic platform, based on the interaction between physisorbed Protein A (PA) and rabbit Immunoglobulin G (rIgG) [1]. In this contribution, a more complex device based on a sub-nL reaction chamber is presented for multi-step immunological reactions.

Multi-inlet chip for electrokinetic immunometric hetrogeneous immunoassay (poster)

A 2 by 3 cm glass chip has been microfabricated and tested with a rabbit immunoglobulin G/protein A affinity model with the aim of implementing immunometric heterogeneous immunoassays. Assays could be performed in times down to 2 minutes. The binding rate constant has been extracted from the obtained data and calculated based on a first order chemical reaction model.

Studies of Hydrostatic Pressure Effects in Electrokinetically Driven μTAS

Possible problems stemming from hydrostatic pressure effects in electrokinetically driven, chip-based analysis systems have been alluded to in the literature, but to date, no detailed study has appeared. This paper discusses the dependence of electroosmotic flow (EOF) on hydrostatic pressure (PH) in etched microchannels of constant cross-sectional area. In addition, video studies show that under certain EOF/PH conditions, bi-directional flow can be observed in microchannels. In a channel whose cross-sectional area varies over its length, this can lead to the establishment of circulatory flow patterns. This type of effect and the conditions needed to generate it are also described.