Video microscopic high-temperature measurement of surface tension

In this paper, a micropipette-in-microcapillary method and its experimental setup are described for the study of temperature effects on surface tension. Temperature control within the confined space of a capillary was achieved by coating the outer surface of the housing microcapillary with an electrically conductive, transparent, tin-doped indium oxide (ITO) thin film as a heating jacket. The precision of this technique was discussed according to the comparisons of our results with published reference data for water, n-hexadecane, and n-decane at room temperature. The technique was further used to measure the temperature-dependent surface tension of n-decane between 25°C and 110°C and n-hexadecane from 25°C to 200°C. The results were in excellent agreement with available published values, and also indicated linear decrease rates of surface tension with decreasing temperatures.