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During winter months, frost can unleash icy havoc on cars, planes, heat pumps, and much more. But thermal defrosting with heaters is very energy intensive, while chemical defrosting is expensive and toxic to the environment.

Jonathan Boreyko, associate professor of mechanical engineering at Virginia Tech, and his research team may have found a new and improved method for deicing. His philosophy is to combat ice by exploiting its own physics instead of using heat or chemicals, creating methods of frost removal that are more cost effective and environmentally friendly.

Their previous work leveraged the small amount of voltage that naturally exists within frost to polarize a nearby water film, creating an electric field that could detach microscopic ice crystals.

Now his team is amping up this concept by applying a high voltage to an opposing electrode to more forcibly dislodge frost from its surface. The result is a new method the team has named "electrostatic defrosting" (EDF). The approach to creating it has been published in Small Methods.

Charging forward

As frost crystals grow, the water molecules arrange into a tidy ice lattice. But sometimes a water molecule lands a little off-pattern鈥攎aybe it has an extra hydrogen nearby (H₃O⁺) or is missing one entirely (OH^鈥�). These tiny errors create what scientists call ionic defects: places in the frost where there is a bit too much positive or negative charge.

The team hypothesized that when applying a positive voltage to an electrode plate held above the frost, the negative ionic defects would become attracted and "migrate" to the top of the frost sheet, while the positive ionic defects would be repelled and migrate toward the base of the frost.

In other words, the frost would become highly polarized and exhibit a strong attractive force to the electrode. If this attractive force is strong enough, frost crystals could fracture off and jump into the electrode.

Even without any applied voltage, the overhanging copper plate removed 15% of the frost. This is because frost can weakly self-polarize even without any applied electric field. However, applying voltage dramatically boosts the extent of polarization. When the team turned on 120 volts of power, 40% of the frost was removed. At 550 volts, 50% was removed.

"We really thought we were onto something here," Boreyko said. "Keep turning up the voltage and more frost will jump away, right? What was unexpected was when the opposite happened."

Turning up the power further, something curious happened: less frost jumped away, reducing to only 30% removal at 1,100 volts and 20% at 5,500 volts. The results contradicted the theoretical model, which predicted that the performance should continually improve with increasing voltage.

The team found a possible explanation for this plunge in frost removal at higher voltages. When growing frost on an insulating glass substrate, rather than a copper one, the higher voltages performed only slightly worse. This indicated that charge leakage from the polarized frost into the underlying substrate was occurring, especially at high voltages, which could be mitigated by using a more insulating surface.

Upgrading again to an air-trapping superhydrophobic substrate, now the highest voltage removed the most frost, as initially expected. Turning up the voltage now ripped off up to 75% of the frost.

"When using the superhydrophobic surface, the electrostatic defrosting was powerful enough to make a hidden Virginia Tech 'VT' logo become clearly visible on the surface after the frost jumped off," said Venkata Yashasvi Lolla, the lead researcher on the project, now in postdoctoral work at Berkeley.

The research continues, toward the eventual goal of 100% ice removal. Part of this research will include the removal of frost on multiple types of surfaces, expanding the potential applications across both industrial and consumer use.

"This concept of electric deicing is still in a very early stage," Boreyko said.

"Beyond this first paper, our goal is to improve EDF by reducing charge leakage and attempt higher voltages and electrode placements, among various other emerging strategies. We hope that in the near future, EDF will prove to be a cost-effective, chemical-free, and low-energy approach to deicing."