title: Radial wettable gradient of hot surface to control droplets movement in directions.
abstract: A radial wettable gradient was fabricated on the surface of graphite plate by a simple one-step anodic oxidation process. It was found that the direction and value of the wettable gradient could be easily controlled by adjusting current and oxidation time gradient. With the increase of surface temperature, droplets on surface not only exhibited the transition of boiling mode, but also showed the controlled radial spreading, evaporation and movement behaviors. These phenomena could be attributed to the cooperation of wettability force, hysteresis force and vapor pressure (Leidenfrost effect). Especially, the controlled radial convergence or divergence of droplets with high velocity were realized on the surfaces with either inside or outside radial gradient, which would have crucial applications in the design of microfluidic devices and the exploration of the biotechnology.
authors.affiliation: Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, Beijing Key Laboratory of Bio-inspired Energy Materials and Devices School of Chemistry and Environment Beihang University. Beijing, 100191 (P. R. China).
authors.forename: Shile
authors.initials: S
authors.lastname: Feng
authors.affiliation: Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, Beijing Key Laboratory of Bio-inspired Energy Materials and Devices School of Chemistry and Environment Beihang University. Beijing, 100191 (P. R. China).
authors.forename: Sijie
authors.initials: S
authors.lastname: Wang
authors.affiliation: Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, Beijing Key Laboratory of Bio-inspired Energy Materials and Devices School of Chemistry and Environment Beihang University. Beijing, 100191 (P. R. China).
authors.forename: Yuanhao
authors.initials: Y
authors.lastname: Tao
authors.affiliation: Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, Beijing Key Laboratory of Bio-inspired Energy Materials and Devices School of Chemistry and Environment Beihang University. Beijing, 100191 (P. R. China).
authors.forename: Weifeng
authors.initials: W
authors.lastname: Shang
authors.affiliation: Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, Beijing Key Laboratory of Bio-inspired Energy Materials and Devices School of Chemistry and Environment Beihang University. Beijing, 100191 (P. R. China).
authors.forename: Siyan
authors.initials: S
authors.lastname: Deng
authors.affiliation: Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, Beijing Key Laboratory of Bio-inspired Energy Materials and Devices School of Chemistry and Environment Beihang University. Beijing, 100191 (P. R. China).
authors.forename: Yongmei
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, Beijing Key Laboratory of Bio-inspired Energy Materials and Devices School of Chemistry and Environment Beihang University. Beijing, 100191 (P. R. China).
authors.forename: Yongping
authors.initials: Y
authors.lastname: Hou