title: Wicking Enhancement in Three-Dimensional Hierarchical Nanostructures.
abstract: Wicking, the absorption of liquid into narrow spaces without the assistance of external forces, has drawn much attention due to its potential applications in many engineering fields. Increasing surface roughness using micro/nanostructures can improve capillary action to enhance wicking. However, reducing the structure length scale can also result in significant viscous forces to impede wicking. In this work, we demonstrate enhanced wicking dynamics by using nanostructures with three-dimensional (3D) hierarchical features to increase the surface area while mitigating the obstruction of liquid flow. The proposed structures were engineered using a combination of interference lithography and hydrothermal synthesis of ZnO nanowires, where structures at two length scales were independently designed to control wicking behavior. The fabricated hierarchical 3D structures were tested for water and ethanol wicking properties, demonstrating improved wicking dynamics with intermediate nanowire lengths. The experimental data agree with the derived fluid model based on the balance of capillary and vicious forces. The hierarchical wicking structures can be potentially used in applications in water harvesting surfaces, microfluidics, and integrated heat exchangers.
authors.affiliation: Department of Mechanical and Aerospace Engineering and ‡Department of Chemical and Bimolecular Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors.forename: Zhiting
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Mechanical and Aerospace Engineering and ‡Department of Chemical and Bimolecular Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors.forename: Junjie
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Department of Mechanical and Aerospace Engineering and ‡Department of Chemical and Bimolecular Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors.forename: Abhijeet
authors.initials: A
authors.lastname: Bagal
authors.affiliation: Department of Mechanical and Aerospace Engineering and ‡Department of Chemical and Bimolecular Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors.forename: Erinn C
authors.initials: EC
authors.lastname: Dandley
authors.affiliation: Department of Mechanical and Aerospace Engineering and ‡Department of Chemical and Bimolecular Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Oldham
authors.affiliation: Department of Mechanical and Aerospace Engineering and ‡Department of Chemical and Bimolecular Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors.forename: Tiegang
authors.initials: T
authors.lastname: Fang
authors.affiliation: Department of Mechanical and Aerospace Engineering and ‡Department of Chemical and Bimolecular Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors.forename: Gregory N
authors.initials: GN
authors.lastname: Parsons
authors.affiliation: Department of Mechanical and Aerospace Engineering and ‡Department of Chemical and Bimolecular Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors.forename: Chih-Hao
authors.initials: CH
authors.lastname: Chang