While commercial flow cytometers are sophisticated analytical instruments extensively used in research and clinical laboratories, they do not meet the challenging practical requirements for point-of-care (POC) diagnostics. Conventional cytometer use all the same basic optical configuration, namely, intense illumination of the bio-particle as it speeds through a highly localized spot, which generally involves a complex arrangement of optics (e.g., lenses, mirrors, apertures, and filters). In this presentation we will describe and illustrate a fundamentally new design of the optical detection system that delivers high effective sensitivity (i.e., high signal to noise discrimination) without complex optics or bulky, expensive light sources to enable a flow cytometer that combines high performance, robustness, compactness, low cost, and ease of use. The enabling innovation is termed spatially modulated emission/excitation and involves relative movement between a fluorescing bio-particle and a patterned environment. This produces a time-modulated signal that is analyzed with real-time correlation techniques. The advantage is high discrimination of the particle signal from background noise. In addition this technique allows discriminating signals from closely spaced particles. The cost benefit arises from the ability to replace expensive, bulky components with inexpensive ones that can be readily integrated on a fluidic chip and by eliminating the need for sophisticated optics and critical optical alignment. The technology will be demonstrated with characterization of individual fluorescent beads (diameters: 6m, 2m and 0.6m), detection of tagged CD4 cells, and CD4 counting in whole blood.
Kiesel, P.; Beck, M.; Bassler, M.; Johnson, N. M. Micro-fluidic-based flow cytometer for point-of-care applications based on a spatial modulation technique . Seminar Talk at the Naval Research Laboratory. Feb. 19th, 2009