Dr. Chang-Hwan Choi of the Department of Mechanical Engineering at Stevens Institute of Technology has been awarded a fourth consecutive Defense University Research Instrumentation Program (DURIP) grant from the ONR to establish new functionalities in his extremely water-repellent surfaces that prevent corrosion in marine vessel surfaces. The latest DURIP grant will be used to acquire a state-of-the-art molecular vapor deposition (MVD) system to facilitate the study and fabrication of multifunctional nanostructured surfaces.
The surface property of being extremely hard to wet, to the extent that water droplets sit extremely high upon a surface (meeting it at an angle exceeding 150 degrees) and roll off at a tilt angle of less than ten degrees, is called superhydrophobicity. In recent years, materials scientists and engineers have sought to understand and apply superhydrophobicity for use in marine vessels and military vehicles that are susceptible to the long-term effects of exposure to seawater, which contains chlorine ions that corrode their aluminum-based surfaces.
“The U.S. General Accounting Office estimated the cost of corrosion to the Department of Defense at between $9 billion and $20 billion annually, and corrosion costs for every US industry sector combined amount to an estimated $276 billion dollars annually according to the Department of Transportation,” says Dr. Michael Bruno, Dean of the Charles V. Schaefer, Jr. School of Engineering and Science. “Technologies like Dr. Choi’s superhydrophobic surfaces, which can avoid or slow corrosive processes in a more cost-effective manner, would have a substantial financial impact for the military and the general population, potentially saving taxpayers billions of dollars.”
In order to limit the excessive costs of corrosion, Dr. Choi has been working to develop surfaces patterned at extremely minute scales to repel water, minimizing contact with seawater and slowing down the corrosive process. In addition to the anti-corrosive properties, his superhydrophobic surfaces have the potential to prevent biofouling (the accumulation of microorganisms, plants and algae) and provide hydrodynamic drag reduction to allow vessels to move more efficiently through water.
The MVD system can deposit individual nano-layers, nano-laminates, and/or organic/inorganic hybrid films typically ranging from 2-500 Å (0.2-50 nm) in a smooth, uniform manner while avoiding the risk of contamination from solvents used in other deposition processes. It is an ideal solution for obtaining molecular-scale superhydrophobic coatings for various types of nanostructured surfaces, allowing Dr. Choi to prototype novel nanostructural concepts and elucidate the nanoscale interfacial phenomena and functionalities. Furthermore, the system offers a static deposition mode for minimal use of chemical precursors, making the MVD method the “greenest” deposition solution in the market today. The system’s unique features and versatility is critical for the understanding and realization of novel multifunctional nanostructures for a wide range of naval applications including anti-corrosion, anti-biofouling, and hydrodynamic drag reduction.
The new instrumentation will also directly support two educational initiatives underway at Stevens: a new cross-disciplinary PhD concentration in Nanotechnology and a Nanotechnology Undergraduate Education program. According to Dr. Frank Fisher, Interim Director of the Department of Mechanical Engineering, “These initiatives strongly complement the technical merit of the acquisition by greatly increasing the number of students exposed to the MVD system and the research projects leveraging its capabilities.”
Dr. Choi previously received a DURIP grant in 2011 to fund an environmental scanning electron microscope (ESEM) that enhanced his study of the functionalities of novel prototypes of nanostructured materials. The ESEM allows his lab to study and observe the wetting dynamics of water—phenomena such as condensation and evaporation—on nano-patterned superhydrophobic surfaces.
In 2010, he also received a DURIP grant to fund a state-of-the-art thin film deposition system. This instrumentation allows Dr. Choi to deposit layers of light metals such as aluminum, which is commonly used in naval applications, with engineered nanocharacteristics that create a water-repelling surface.
About the Department of Mechanical Engineering
The Department of Mechanical Engineering confidently addresses the challenges facing engineering now and into the future, yet remains true to the vision of the founders of Stevens Institute in 1870 as one of the first engineering schools in the nation. The department mission is to produce graduates with a broad-based foundation in fundamental engineering principles and liberal arts together with the depth of disciplinary knowledge needed to succeed in a career in mechanical engineering or a related field, including a wide variety of advanced technological and management careers. This is accomplished through a broad-based Core Curriculum of applied sciences, engineering sciences, design, management, and the humanities, coupled with a long-standing honor system.
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