A microfluidic device that uses single cell impedance spectroscopy is being developed as part of a Point of Care system capable of perfoming a full blood count (FBC) from a fingerprick of blood. In particular, this project focuses on the discrimination of the five different white blood cell types. Cells are introduced to the device and flow at high speed through the detection zone of a pair of microelectrodes, from which the differential signal provides information on both cell size and dielectric properties.
Treatment of whole blood with a lysis solution currently allows differentiation between the three main white blood cell types: granulocytes, lymphocytes and monocytes (see figure). One of the project objectives is to distinguish the less abundant eosinophils and basophils from neutrophils in the granulocyte population. Laser illumination of the cells enables comparison with fluorescence measurements of specific cell markers, the current 'gold standard' of cell identification. The ultimate aim is to produce a low-cost, compact impedance sensor that does not rely on the use of fluorescent labelling.