HANOVER, N.H.- With winter weather approaching in colder climates, travelers face daily frustrations of scraping away the ice clinging to steps and vehicle glass surfaces. There are also impending risks of power outages caused by ice storms. For the military, icy conditions threaten the safety and success of global operations by severing communication and utility networks, halting transportation and interfering with visibility.
For one inventor at the U.S. Army Corps of Engineers Research and Development Center’s (ERDC) Cold Regions Research and Engineering Laboratory (CRREL), such ice adhesion scenarios are rich with research questions, leading to her invention, which enables high-fidelity control over ice growth on surfaces for ice adhesion research.
Research materials engineer Dr. Emily Asenath-Smith received a patent in August 2022 for her invention, “Vertical draw system and method for surface adhesion of crystalline materials,” a foundational component of her ice adhesion research program.
CRREL Research Facility Advantages
CRREL, located in Hanover, New Hampshire, has extensive environmental laboratories that allow for temperature control below freezing.
“The development of our vertical draw tower was performed in some of CRREL’s newer cold rooms, which have digital temperature controllers, redundant cooling systems and backup electrical power,” Asenath-Smith said. “While these rooms go as cold as -40 ºC, we stayed around -10 ºC for most of this research.”
Asenath-Smith is the lead investigator for CRREL’s Ice Adhesion Facility, where much of her innovative research is conducted. As the recipient of a prior patent, Asenath-Smith is recognized for her expertise in materials science, bio-inspired material synthesis, adhesion, interfacial phenomena and energy transfer materials.
Along with CRREL co-inventors Garrett Hoch, research electrical engineer; Christopher Donnelly, mechanical engineering technician; and Jordan Hodge, engineering technician; Asenath-Smith will be honored with a patent plaque presentation by ERDC’s Office of Research and Technology Transfer (ORTT) which processes patents for the Center.
Ice Removal Challenges
“Ice wreaks all kinds of havoc on cold weather operations. The best-case scenario is that our troops have to shelter in place, an approach that has many risks of its own,” Asenath-Smith said. “Worst-case scenario is loss of life and critical assets. In civilian sectors, utilities lines are lost, communications severed and transportation halted.”
“There currently exist methods to mitigate ice, but they are either energy intensive or environmentally unfriendly; referred to as active methods,” she explained. “For example, de-icing fluids used on roadways and aircraft have negative environmental impacts, and thermal deicing methods require power and often increase vehicle mass.”
“The true holy grail is to develop passive ice mitigation methods, which prevent ice adhesion, or facilitate ice removal without any energy input or increase in mass,” Asenath-Smith said. “Such passive methods are generally coatings or surface treatments, which function based on the chemistry and physics of the surfaces, allowing them to operate without additional energy or mass. There are some very promising surface treatments and coatings for ice mitigation that have been developed and tested at the lab scale.”
“However, few of these technologies have been transitioned to military applications. The barrier stems from the lack of an analytical framework for assessing the ice mitigation performance of a coating,” she said, adding that “with my research team, I am working on developing quantitative metrics that describe the performance of ice mitigation technologies, across length scales, so that stakeholders can make informed decisions about whether to deploy these new coating technologies on their assets.”
How the Invention Works
Asenath-Smith explained that ice adhesion is assessed by measuring the force required to remove ice that has adhered to the surface. She shared that there are many geometries and configurations utilized in these studies, and there isn’t a consistent way that the ice is adhered to the surface of interest. Her invention enables the growth of ice directly on surfaces without the use of molds and produces, an outcome that reduces uncertainty and scatter in the experimental ice adhesion data.
Asenath-Smith conceived this invention by taking a broad look at the fundamentals.
“We were ‘just’ trying to crystallize ice on a surface, directly from its melted form (water), and this is no different than growing a ceramic crystal from its melt at high temperature,” she explained.
With that perspective, Asenath-Smith led her team in developing a prototype device to crystallize ice on a flat specimen in a way that is analogous to how single crystal semiconductors are grown at high temperatures. Her invention is based on a vertical draw method, where the specimen of interest is inverted and brought into contact with the surface of a reservoir of water. Ice is nucleated immediately on the specimen’s surface, forming a layer that can be grown to variable thicknesses by pulling the specimen away from the water.
“With our invention, we can precisely control the microstructure of the ice layers during growth on surfaces to produce single crystal ice layers or polycrystalline ice layers, with randomly oriented or ordered columnar microstructure,” Asenath-Smith said.
To accomplish this versatility, Asenath-Smith said that water temperature and the specimen are well-controlled, so that ice forms only on the specimen.
“As we controllably pull it away from the water surface, the ice continues to grow on the specimen surface, forming an ice layer that resembles the specimen shape,” she explained. “Thickness of the ice layer can vary from millimeters up to centimeters. Most commonly, we grow ice laminates that are one cm thick. Unlike crystallization of ceramic and semiconducting materials where a single crystal (boule) is the goal, we developed our ice growth method to produce polycrystalline ice with a microstructure that has columnar grains.”
Next Research Steps
Citing the advantages of this now-patented method and device, Asenath-Smith said that growing ice with consistent microstructures on surfaces for adhesion studies is a fundamental enabler of other research.
Now that ice growth on surfaces is well-controlled and characterized, her team’s research can focus on the role of surface and coating material properties on ice removal from surfaces.
“Such studies will enable the development of an analytical framework to describe the performance of coatings and materials for ice mitigation,” Asenath-Smith said. “Such outcomes will ensure that advanced coating technologies that mitigate icing catastrophe are developed and transitioned to the military and civilian sectors.”
For additional technical information, access the patent application at: https://patents.justia.com/patent/20210262118