Lab-on-a-chip systems offer a versatile environment in which low numbers of cells and molecules can be manipulated, captured, detected and analysed. We describe here a microfluidic device that allows the isolation, electroporation and lysis of single cells. A431 human epithelial carcinoma cells, expressing a green fluorescent protein-labelled actin, were trapped by dielectrophoresis within an integrated lab-on-a-chip device containing saw-tooth microelectrodes. Using these same trapping electrodes, on-chip electroporation was performed, resulting in cell lysis. Protein release was monitored by confocal fluorescence microscopy.

Extraction of a GC-amenable hydrocarbon fraction from oil by liquid-liquid diffusion across a laminar interface can be performed in a microfluidic format. Analysis of figures of merit, determined using standard analytical techniques, show this method to be an effective new tool for rapidly processing small quantities of oil and petroleum for GC analysis. Methods based upon similar microsystems devices could find widespread use in a variety of fields, including those associated with organic geochemistry and oil exploration and production, where the manipulation of petroleum constituents (greater than C-14) is necessary for analytical purposes.

A microfluidic based device has been developed for the continuous separation of polymer microspheres, taking advantage of the flow characteristics of systems. The chip consists of an asymmetric cavity with variable channel width which enables continuous amplification of the particle separation for different size particles within the laminar flow profile. The process has been examined by varying the sample inlet position, the sample to media flow rate ratio, and the total flow rate. This technique can be applied for manipulating both microscale biological and colloidal particles within microfluidic systems.

Raman spectroscopy is a form of vibrational spectroscopy that is well suited to the molecular identification of a variety of analytes, including both explosives and biological agents. The technique has been gaining more widespread interest due to improvements in instrumentation, sensitivity, and its ease of use, in comparison to other techniques. In this paper, we describe recent advances in Raman spectroscopy with respect to the detection of high-energy explosives and biological materials. In particular, emphasis is placed on the exploitation of enhancement factors that overcome traditional limitations on sensitivity, namely, surface enhancement and resonance enhancement, functionalization of target analytes, and the use of novel lab-on-a-chip technology.

Surface-enhanced resonance Raman scattering (SERRS) is considerably more efficient than Raman spectroscopy, thereby enabling the detection of single molecules. Strong and short-lived SERRS emissions (<100 ms) from single, partially silver-coated, dye-adsorbed microparticles have been detected within optical tweezers (see picture). Full spectra, recorded from single particles, clearly show that the emission is due to SERRS.

The first simultaneous detection of three dye-labelled oligonucleotides in a microfluidics chip by SERRS is reported.