DYNAMIC SURFACE-TENSION MEASURED WITH AN INTEGRATED SENSOR-ACTUATOR USING ELECTROLYTICALLY GENERATED GAS-BUBBLES

In this paper, a new, simple method to determine dynamic surface tensi on in aqueous solutions is reported, explained and experimentally veri fied. By function integration, a small device is obtained. Apart from control and interface electronics no external components or systems ar e necessary. Instead of the conventional sparging, we use the (cathodi c) electrolysis of water at an actuator to produce gas bubbles in situ . The actuator can also function as the sensor for the bubble frequenc y by monitoring either its overpotential or its impedance. A simple mo del is given, by which the dependency of the bubble frequency on the d ynamic surface tension can be predicted. Experimental results are in a greement with this model and show the feasibility of the proposed meth od. (C) 1998 Elsevier Science S.A. All rights reserved.