A novel capillary-based flow cell for flow cytometry

Flow cytometry is an analytical technique used in biomedical diagnostics, that measures properties of cells, micro-organisms and particles. Laser light is scattered from particles focused in a flowcell and collected by light sensors (photodiodes) where the intensity of the scattered light is a function of the scattering angle, refractive index of the particle and surrounding medium, wavelength of light and size and the shape of the particle. One of the critical parts of the cytometer is the flow cell where the particle stream is constrained into a tight region using hydrodynamic focusing. The conventional flow cells use thick quartz flow cells, they are expensive, therefore not suitable for instruments targeted for resource-constrained settings. We propose a low-cost sheath flow assembly design made of micro-tight ETFE adapters and an assembly of capillary tubes for passage of focused flow of particles. The entire flow cell assembly is a simplified version of a sheath flow cuvette design able to focus and accelerate a stream of particles in a narrow region probed by the incident laser. We show excellent agreement between size distribution obtained via direct imaging and those obtained from light scattering. With minor modifications, the device may be used for disease detection.