Electrical-conductivity SFM study of an ultrafiltration membrane

A method for local investigation of ultrafiltration membrane pore networks has been developed in order to complement bulk measurements and calculations. An Anopore(TM) membrane (200 nm) pore network was filled with electrodeposited nickel. Membranes were analysed simultaneously with normal scanning force microscopy (SFM) and electrical-conductivity SFM. Cantilevers coated with 10 Omega cm diamond were used to map both normal force and conductivity. Conductivity images show two kinds of pores: bright pores with diameters of 192 +/- 2 nm and grey pores with diameters of 172 +/- 5 nm, depending on the depth of the nickel tubes. The average pore diameter measured from the normal SFM images is 217 +/- 3 nm, and the ratio of the conductive pores to total number of pores is 49.8%. Preferential flow paths can be established from this technique.