## 2 Materials and Methods
### Multi-Tool Analysis
#### 3.1.2 MTA vs. Low-Intensity ZR  
The second type of icing simulated was low-intensity freezing rain. The results are presented in Figure 9 as the weigh percentage of remaining ice as a function of tools and the number of passages. The corresponding picture after icing is illustrated in Figure 5. At the lower intensity of freezing rain precipitation, the materials' hydrophobic properties are more effective and can therefore delay the solidification of water droplets or cause them to solidify in beaded form. In this case, an additional tool was added that was stiffer than the soft polymer blade (B) but less than the solid polymer blade (D), namely the squeege  
Figure 8: Multi-tool analysis under high-intensity freezing rain. Note: Numbers correspond to the tool used and number of passages during de-icing. Where “20 to 16” represent the broom, “15 to 11” represent the soft polymer blade, “10 to 6” represent the hard polymer blade, “5 to 1” represent the ridged polymer blade, and 0 indicates that ice remained on the surface.  
(tool C). The aluminum surface was again observed to be the least favorable one, not allowing for the complete de-icing after the passage of all tools. In the case of the SurfEllent coating, however, the soft polymer blade (B) was able to partially remove some of the ice. In almost all cases, the use of tool C (squeegee) removed most of the contaminants from the Wearlon- and SurfEllent-coated surfaces. Nevertheless, the use of the solid blade was necessary to remove some residual contamination present on the Nusil surface. Note that the ski wax was not tested in this condition. However, we can assume that a similar result to the previous condition would be obtained.  
A simple 2D representation of ice covering two different tested materials is presented in Figure 10 below. The left portion of the figure shows how ice typically accumulates on an aluminum surface. The ice is shown to cover the surface uniformly, exploiting the available roughness and all anchoring points, which in turn increases ice adhesion. In the same manner, when the MTA is applied using soft tools, such as the broom and the polymer, they are not rigid enough to break the adhesive bond with the surface. Instead, the cohesive bonds are first broken within the ice itself followed by the breakage of adhesive bonds. Therefore, a harder tool, such as hard and ridged polymer, is needed to effectively remove the ice. In the case of hydrophobic materials, such as a Nusil coating for example, the film of ice is not uniform, as represented in the right portion of Figure 10. The higher contact angle and the longer freezing delay of the material causes the water to agglomerate in large beads (droplets) prior to freezing. This effect is more noticeable when the precipitation rate is low. However, since the surface is hydrophobic, the ice covering the surface is less uniform, which reduces the adhesion of ice compared to that of aluminum alone. Hence, the passage of a soft tool allows for the gradual removal of small pieces of ice with substantially less effort. In essence, there is no need to break the cohesive bond prior to the adhesive bond since it is weaker when compared to the reference aluminum surface.  
Figure 9: Multi-tool analysis under low-intensity freezing rain. Note: Numbers correspond to the tool used and the number of passages during de-icing. Where “20 to 16” represent the Broom, “15 to 11” represent the soft polymer blade, “10 to 6” represent the squeeegee, “5 to 1” represent the hard polymer blade, and 0 indicates that ice remained on the surface.