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Capillary Rise of Nanostructured Microwicks

School of Chemical, Biological, and Environmental Engineering, Oregon State University, Corvallis, OR 97331, USA
Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Nam-gu, Pohang-Si, Gyungsangbuk-do 37673, Korea
Battelle/Pacific Northwest National Laboratory, MicroProducts Breakthrough Institute, 1000 NE Circle Boulevard, Suite 11101, Corvallis, OR 97330, USA
Department of Mechanical Engineering, Indian Institute of Technology, Bombay, Mumbai 400076, India
Author to whom correspondence should be addressed.
Micromachines 2018, 9(4), 153;
Received: 10 February 2018 / Revised: 21 March 2018 / Accepted: 26 March 2018 / Published: 28 March 2018
PDF [25468 KB, uploaded 3 May 2018]


Capillarity refers to the driving force to propel liquid through small gaps in the absence of external forces, and hence enhanced capillary force has been pursued for various applications. In this study, flower like ZnO nanostructures are successfully deposited to enhance capillarity of microwick structures that are specially designed to augment boiling heat transfer performance. Microreactor-assisted nanomaterial deposition, MANDTM, is employed with a flow cell to deposit the ZnO nanostructures on a large sized microwick (4.3 cm × 10.7 cm) with dual-channel configuration. A capillary rise experiment based on the mass gain method is first performed using water and ethanol (EtOH) as the working liquids to demonstrate the enhanced capillary force induced by the ZnO nanostructure on the microwick structure. It is found that the coating of ZnO nanostructure effectively propels the working fluids through the nano- or micro pores created from the ZnO nanostructure and consequently improves the capillary force. In order to investigate the wicking mechanism of the ZnO coated microwick structure, the capillary rise result based on height measurement was compared with analytical models. It is found that the gravity effect and viscous force play an important role in wicking rise of the coated wick structure. This study aims at demonstrating the capability of the integrated MAND process with a flow cell for producing a large scaled nanostructured surface, which eventually has a great potential for enhanced boiling heat transfer. View Full-Text
Keywords: ZnO nanostructure; capillary wicking; ZnO nanoparticle assembly ZnO nanostructure; capillary wicking; ZnO nanoparticle assembly

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Choi, C.-H.; Krishnan, S.; TeGrotenhuis, W.; Chang, C.-H. Capillary Rise of Nanostructured Microwicks. Micromachines 2018, 9, 153.

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