(677c) Disruption of Ice Adhesion through Surface Functionalization

Authors: 
Schweitzer, B., South Dakota School of Mines and Technology
McDougall, N., South Dakota School of Mines and Technology
Smith, J., NASA
Wohl, C., NASA
Kreeger, R., NASA

Disruption of ice adhesion through surface functionalization

Ice adhesion is a problem that impacts a wide range of commercial and industrial environments, including aviation. One major issue in aviation is ice formation on the aircraft causing reduced lift of wing and increased drag. The current strategy to mitigate ice formation is a combination of deicing spray and deicing boots on planes to both remove accumulated ice and prevent ice formation. These active methods are not entirely effective, increase vehicle operation complexity, and have environmental and economic concerns associated with their use.

The goal of this work was to develop a passive method to mitigate ice formation using a functionalized polymer coating. Previous work into this area utilized modified superhydrophobic surfaces. While this method is effective versus impacting droplets, it provides little capability in mitigating ambient frost formation. Instead, our work takes a biomimetic approach to a passive strategy for ice mitigation. In species of artic fish and amphibians, anti-freeze proteins prevent internal crystallization of the water found near the proteins. This is made possible by the proteins due to strategically placed hydrophilic side groups. The ultimate goal of this work is to develop a polymeric coating to mimic the functionality of anti-freeze proteins. In order to guide the experimental design of the polymeric coating, a number of functional moieties are studied through short chain modification of a surface.

To support this effort, we are presenting molecular dynamic (MD) simulations of ice crystals interacting with the modifiers attached to silica. MD simulations allows for efficient screening of different functionalities while providing a molecular level insight into the ice/surface interface. From our previous simulations, we have found that the disruption of the adhesion interface can be monitored through measuring the thickness of the quasi-liquid layer (QLL). The QLL is a layer of interfacial water with properties similar to liquid water. The thickness of the QLL can be assessed by measuring density, mean squared diffusion, and characterization the hydrogen bonding network.

With an effective method for assessing anti-icing efficacy, we will present a comparison of how well different functionalities affect the ice/surface interface.  The focus will be on comparing the impact of different hydrogen-bonding functionalities (alcohols, ethers) against hydrophobic functionalities (alkanes, fluoroalkanes).

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