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.

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► A micropipette-in-microcapillary setup was used for surface-tension measurements.
► Electric current passing through a coated ITO film produced high temperatures.
► γ of n-decane was measured up to 110 °C, and of n-hexadecane up to 200 °C.
► The measured surface tensions show excellent agreement with reported values.