| A wide range of bioanalytical demonstrations on Micro Total Analysis Systems, μTAS, has established the advantageous features of planar microfluidic devices. However, practical problems, such as the difficulty of chip interfacing could limit the use of μTAS. We describe a novel, reversible and simple chip-to-capillary interface, which withstood working pressures of up to at least 20 atm and allowed for the coupling of capillaries to glass chips with moderate dead volume.; The construction of a confocal epifluorescence microscope for on-channel detection is described, wherein a 40x, 0.6 numerical aperture (N.A.) lens is used to focus a laser beam to an excitation spot of 12 μm diameter. A 400 μm pinhole showed optimum signal to noise, S/N, ratios for 30 μm deep, isotropically etched, glass channels. Continuously pumped fluorescein solutions, 300 fM in concentration, were detected with an average S/N, of 6.1. The lowest detectable concentration of electrokinetically injected fluorescein plugs was 1 pM (average S/N = 5.8), corresponding to 570 detected molecules on average.; A β-Galactosidase assay of single cell lysates on a microchip is illustrated for the first time. A nondenaturing 400 μM FDG and 0.1% Triton®X-100 solution is mixed with a single cell stream at a mixing ratio of ∼1:1 and a flow velocity of ∼40 μm/s, followed by lysis for 30–60 s, incubation of single cell lysates for ∼80–110 s and on-chip fluorescence detection. Inherent drawbacks of conventional single cell analysis tools, such as flow cytometry, can be circumvented by integrating single cells analysis steps as demonstrated in this study.; Unmodified Polydimethylsiloxane, PDMS, an inexpensive and hence disposable device material, was investigated for chip-based capillary electrophoresis. The devices exhibited cathodic electroosmotic flow when in contact with phosphate buffers (pH 3–10.5) and stable retention times (±8.6% RSD) over a period of 5 days when filled with water. Contact angles were unchanged (±1.9% RSD) over a period of 16 weeks of dry storage. Tight definition of fluorescein plugs was obtained by continuous voltage control of all fluidic ports, yielding 64200 theoretical plates (E = 1340 V/cm). The charge origin on PDMS surfaces was investigated and self-adhesive, microfluidic 3D PDMS manifolds were constructed. |
