Abstract: Disclosed is a device for determining a concentration of cells of a given size in a sample of fluid, the sample comprising a plurality of cells, comprising: a light source arranged to emit light along a central axis to illuminate the plurality of cells in the fluid sample; a detector arranged to receive light at a plurality of displacements from the central axis, the light having passed through the plurality of cells in the fluid sample, and to produce a plurality of signals, each associated with, and indicative of an intensity of the received light at, a respective one of the plurality of displacements; and a processor arranged to determine a concentration of cells of a given size, based on the plurality of signals from the detector, wherein the processor is arranged to compare the plurality of signals from the detector with one or more pre-stored thresholds or profiles, indicative of a particular concentration.

Abstract: Apparatus for detecting particles in a liquid, comprises an evanescent optical sensor having an electrically conducting layer, and means associated therewith for providing an electric field at or adjacent the sensor surface. Preferably, the optical sensor is a surface bound sensor based on a metal-clad leaky waveguide structure. A DC potential applied to the metal layer and a parallel counter electrode provides a uniform electric field, which drives deposition of the particles on the sensor surface. Alternatively, an alternating potential applied to a electrically conducting layer configured as an electrode and counter electrode induces an electro-osmotic bulk flow in the liquid which drives deposition of the particles on the sensor surface.