The present invention relates to a particle characterization apparatus inwhich particles suspended in a liquid passes through an orifice or aperturefor detection and characterization of the particles utilising impedancedetermination. In particular the invention relates to utilisation of amembrane of a polymer as a base material for precision machining of a sub-millimetre orifice. Forming the orifice in a polymer membrane facilitates theconstruction of a single use cartridge for haematology analysis due to lowmaterial and production costs.
