Electrocapillarity is the basis of modern electrowetting. And room temperature ionic liquids, an increasingly important set of electrolytes and organic salts that are liquid at room temperature, are considered a novel class of electrowetting agents, because of non-significant vapor pressure, nonflammability, good thermal stability, and a wide useable temperature range. In this paper, a simple device has been fabricated to investigate the electrocapillarity of ionic liquids. It shows attractive features involving wide operating temperature and in particular high stability, fast response and good reversibility at high temperatures. Besides, electrocapillarity of ionic liquids is strongly dependent on power supply frequency. In particular, high frequency, stable, reversible and wide height of rise modulations were obtained. The phenomenon of ionic liquids-based electrocapillarity was found to be affected by the structure and physicochemical properties of ionic liquids such as density, surface tension, alkyl carbon chain length of cation, type of the anion, etc., and the efficiency could be further improved through optimal choice of ambient phase or rational design and synthesis of ionic liquids. (C) Koninklijke Brill NV, Leiden, 2011