Direct observation of stick-slip movements of water nanodroplets induced by an electron beam

作者：Mirsaidov Utkur M; Zheng Haimei; Bhattacharya Dipanjan; Casana Yosune; Matsudaira Paul^*

来源：Proceedings of the National Academy of Sciences of the United States of America, 2012, 109(19): 7187-7190.

DOI：10.1073/pnas.1200457109

• interfacial water
• nanoscale fluids

Dynamics of the first few nanometers of water at the interface are encountered in a wide range of physical, chemical, and biological phenomena. A simple but critical question is whether interfacial forces at these nanoscale dimensions affect an externally induced movement of a water droplet on a surface. At the bulk-scale water droplets spread on a hydrophilic surface and slip on a nonwetting, hydrophobic surface. Here we report the experimental description of the electron beam-induced dynamics of nanoscale water droplets by direct imaging the translocation of 10- to 80-nm-diameter water nanodroplets by transmission electron microscopy. These nanodroplets move on a hydrophilic surface not by a smooth flow but by a series of stick-slip steps. We observe that each step is preceded by a unique characteristic deformation of the nanodroplet into a toroidal shape induced by the electron beam. We propose that this beam-induced change in shape increases the surface free energy of the nanodroplet that drives its transition from stick to slip state.

• 出版日期2012-5-8