By Josh Perry, Editor
[email protected]

Researchers at Pennsylvania State University (University Park, Pa.), the University of Virginia (Charlottesville, Va.), and the National Institute of Standard and Technology (NIST) in Maryland have developed a new bioprotein film from the DNA in squid ring teeth that has low thermal conductivity at ambient humidity but that increases conductivity dramatically as the humidity rises.

Graph showing cycles of thermal conductivity when material is wet and then dry.
(Melik Demirel/Penn State University)

According to an article from Penn State, unlike common plastics, which are thermal insulators, the tandem repeats in the DNA from squid ring teeth make this bioprotein film 4-1/2 times better at conducting heat.

“One potential use of this bioprotein film might be as a fabric coating, especially for athletic wear,” the article explained. “The material could be perfectly comfortable and cozy in everyday use, but when actually used for heavy activity, the sweat produced by the wearer could ‘flip’ the thermal switch and allow the fabric to remove heat from the wearer’s body.”

Scientists created synthetic proteins patterned on tandem repeating sequences. When ambient conditions are lower than 35 percent humidity, the proteins behave similar to common polymers but when they become wetter (e.g., from humidity or sweat) the number of tandem repeats increases and thermal conductivity improves.

“When the material returns to normal ambient humidity or lower, the switch turns off, and the protein no longer conducts heat as efficiently,” the article continued.

The research was recently published in Nature Nanotechnology. The abstract stated:

“The dynamic control of thermal transport properties in solids must contend with the fact that phonons are inherently broadband. Thus, efforts to create reversible thermal conductivity switches have resulted in only modest on/off ratios, since only a relatively narrow portion of the phononic spectrum is impacted.

“Here, we report on the ability to modulate the thermal conductivity of topologically networked materials by nearly a factor of four following hydration, through manipulation of the displacement amplitude of atomic vibrations. By varying the network topology, or crosslinked structure, of squid ring teeth-based bio-polymers through tandem-repetition of DNA sequences, we show that this thermal switching ratio can be directly programmed.

“This on/off ratio in thermal conductivity switching is over a factor of three larger than the current state-of-the-art thermal switch, offering the possibility of engineering thermally conductive biological materials with dynamic responsivity to heat.”