ABSTRACT
Droplet motion on a solid surface is an important and interesting topic (Grunze 1999, Wasan et al. 2001) in both fundamental research and real applications such as microfl uidics (Gau et al. 1999, Zahner et al. 2011), fi ltration, water collection (Bai et al. 2011, Bai et al. 2014), and condensers. For example, microfluidic systems involving self-powered droplets would be more energy-favorable. Condensers with smart surfaces where condensed droplets can be removed by their spontaneous motion would be more effi cient in heat exchange (Daniel et al. 2001). Water collectors could even collect very tiny droplets which usually evaporate into air again after hitting on the surface by controllably driving them towards each other and forming larger droplets (Ju et al. 2012, Parker and Lawrence 2001, Zheng et al. 2010). As a result, there are always pressing needs for developing smart surfaces for controlled droplet motion.
