Electrocavitation in Nanochannels

Abstract

A novel method has been developed to cavitate aqueous solutions, which is called electrocavitation. An axial voltage is applied in a nanochannel containing an aqueous solution with a stepwise conductivity gradient. A combination of electrical and viscous forces then generates a tension in the solution which, at sufficiently low pressures, causes it to cavitate. Measurement of the current during the experiment as well as optical observation provides knowledge on the time and axial position of cavitation, after which the pressure at the cavitation position can be calculated from a theoretical model in which also the ζ-potential is inserted, which is separately determined from electroosmotic flow experiments. It is found that generally the cavitation position coincides with the position of the conductivity step. In several experiments the cavitation pressure in successive experiments on the same channel became increasingly lower, suggesting a gradual removal of cavitation nuclei from the system. We calculated that pressures as low as −1630 bar ±10 % have been reached, close to theoretically predicted pressures for homogeneous cavitation. The platform performs reliably and can be easily controlled.