Chemistry, Materials & Packaging
Biomimetic, Phase-Changing Materials Could Hold Keys to Climate-Resistant Surfaces

Whether the presidential candidates pay attention to it or not, climate change is a looming threat. Failure of climate change mitigation and adaptation was considered to be the greatest global risk in the World Economic Forum’s newly-released 2016 Global Risks Report. Luckily, researchers are making progress on mitigation and adaptation solutions to combat the changing temperatures, thanks to beetles and adaptive building materials.

The Namib Desert beetle’s bumpy shell is unique: The tips of the bumps attract moisture to form drops, and the sides are smooth and repel water, creating channels that lead directly to the beetle’s mouth. This allows it to survive in harsh climates by collecting and condensing airborne moisture into water it can drink; researchers at Virginia Tech are working to apply that principle to the protection of various surfaces.

“I appreciate the irony of how an insect that lives in a hot, dry desert inspired us to make a discovery about frost,” said Jonathan Boreyko, an assistant professor of Biomedical Engineering and Mechanics at Virginia Tech. “The main takeaway from the Desert Beetle is we can control where dew drops grow.”

Boreyko and his team used photolithography – or transferred geometric patterns from a surface to a silicon wafer – to pattern chemical arrays that attract water over top of a surface that repels water, thereby controlling or preventing the spread of frost. Their research, published on Scientific Reports, an online journal from the publishers of Nature, may lead to ways to prevent frost on airplane parts, condenser coils, and even windshields.

“Fluids go from high pressure to low pressure,” Boreyko explained. “Ice serves as a humidity sink because the vapor pressure of ice is lower than the vapor pressure of water. The pressure difference causes ice to grow, but designed properly with this beetle-inspired pattern, this same effect creates a dry zone rather than frost.”

The researchers were able to create frost-free areas and control the speed the frost grew across surfaces by controlling the spacing of the condensation.

“Keeping things dry requires huge energy expenditures,” C. Patrick Collier, a research scientist and co-author of the study, said. “That's why we are paying more attention to ways to control water condensation and freezing. It could result in huge cost savings.”

This is not the first time that the Namib Desert beetle has inspired technological innovation – the first prize winner in the 2011 James Dyson Awards, Edward Linacre’s Airdrop, is a low-tech, self-sufficient, solar-powered irrigation system that was designed to mimic how the beetle collects moisture from the air to combat drought.

Meanwhile, Arizona State University (ASU) engineer and associate professor Narayanan Neithalath and his team are developing more resilient concrete pavements through experimentation with phase-changing materials. Phase-changing materials are substances that respond to temperature variations by changing their state from solid to liquid or vice versa. By adding them to concrete, the materials may be able to protect the concrete from temperatures that can trigger fractures.

“We know how the materials perform under laboratory conditions. Now we have to see if it holds up when applied at larger scales and real-life loading and environmental conditions,” Neithalath said in a press release.

“The important thing is to have a material that helps concrete pavements cope with different kinds of stresses put on it,” Neithalath added. “You need materials that can melt or solidify in response to varying environmental conditions without weakening the structural integrity of the pavement.”

The research team, which includes other engineers from ASU and from the University of California, Los Angeles (UCLA), are completing a project funded by the National Science Foundation and will soon expand their work.

Their investigation of new high-performance concrete materials is among one of less than 10 projects selected by the European Commission under the new Infravation initiative – an effort which seeks to develop technological solutions at the intersection of infrastructure and innovation. The existing team will collaborate with researchers at Delft University of Technology in the Netherlands, the Swiss Federal Institute for Materials Science (also known as EMPA) and the Tecnalia Research and Innovation organization in Spain.

As part of the expanded project, ASU assistant professor Mikhail Chester will perform cost-benefit analysis as well as life-cycle analysis of the new pavement material, which ASU says is a major step in predicting how it will measure up to sustainability expectations. By enhancing the durability of roads and bridges, the research has implications for improving transportation infrastructure to be more sustainable. Phase-changing materials can be sourced from petroleum (such as paraffin wax) or plant-based sources – adding further potential for greener infrastructure.

“We will have good research teams at each of the institutions in different countries that are partners in this project. We have experts for every component of what we need to accomplish our goal,” Neithalath said. “I think we can take concrete pavements to the next level.”


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