Efficient Self-Propelling of Small-Scale Condensed Microdrops by Closely Packed ZnO Nanoneedles.
Realizing the efficient self-propelling of small-scale condensed microdrops is very challenging but extremely important to design and develop advanced condensation heat transfer nanomaterials and devices, for example, for power generation and thermal management. Here, we present the efficient self-propelling of small-scale condensed microdrops on the surface of closely packed ZnO nanoneedles, as-synthesized by facile, rapid, and inexpensive wet chemical crystal growth followed by hydrophobic modification. Compared with flat surfaces, the nanostructured surfaces with the same low-surface-energy chemistry possess far higher time-averaged density of condensed droplets at the microscale, among which those with diameters below 10 μm occupy more than 80% of the total drop number of residual condensates. Theoretical analyses clearly reveal that this remarkable property should be ascribed to the extremely low solid-liquid adhesion of the surface nanostructure, where excess surface energy released from the coalescence of smaller condensed microdrops can be sufficient to ensure the self-propelled jumping of merged microdrops.
†Advanced Thermal Nanomaterials and Devices Research Group, Nanobionic Division, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, People's Republic of China.|¶University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
Jian
J
Tian
†Advanced Thermal Nanomaterials and Devices Research Group, Nanobionic Division, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, People's Republic of China.
Jie
J
Zhu
‡Department of Engineering Mechanics, Tsinghua University, Beijing 100084, People's Republic of China.
Hao-Yuan
HY
Guo
†Advanced Thermal Nanomaterials and Devices Research Group, Nanobionic Division, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, People's Republic of China.
Juan
J
Li
‡Department of Engineering Mechanics, Tsinghua University, Beijing 100084, People's Republic of China.
Xi-Qiao
XQ
Feng
†Advanced Thermal Nanomaterials and Devices Research Group, Nanobionic Division, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, People's Republic of China.
Xuefeng
X
Gao
condensation; hydrophobic effect; low-adhesive; microdrop self-propelling; nanostructure; surface science