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 tension in aqueous solutions is reported, explained and experimentally verified. By function integration, a small device is obtained. Apart from control and interface electronics no external components or systems are necessary. Instead of the conventional sparging, we use the (cathodic) electrolysis of water at an actuator to produce gas bubbles in situ. The actuator can also function as the sensor for the bubble frequency by monitoring either its overpotential or its impedance. A simple model is given, by which the dependency of the bubble frequency on the dynamic surface tension can be predicted. Experimental results are in agreement with this model and show the feasibility of the proposed method.