From its early applications of cell counting in the 1950's, the Coulter Counter technology continues to be advanced and improved. Increasingly known as resistive pulse sensing/ sensors (RPS), devices based on this principle have now been created from a range of materials from graphene, to polymers, silicon nitride and glass. The sensing process is simple, by monitoring the temporary changes in current caused by the translocation of an analyte through a narrow constriction, termed a sensing region or pore, RPS can characterise analytes according to size, concentration, 13 shape and charge. The transport of an analyte through the pore is controlled by tuning the applied electric field, charge on the pore wall, electrophoretic mobility of the analyte, supporting electrolyte concentration and induced convection. To maintain sensitivity the pore size must be of comparable dimensions as the analyte. Therefore, whilst a smaller sensing region can detect smaller analytes, the drawback is an increases the likelihood of blockages, and a decreased translocation frequency.