Engineers are developing a new class of nanofibers that mimic polar bear fur, lotus leaves, and gecko feet

A newly-engineered class of nanofibers will be able to copy the unique properties found in natural materials. Coatings made from these nanomaterials can match the warmth of the white fur of polar bears, repel water like the lotus plant, and stick to surfaces like the sure-footed geckos.

The nanofibers are the creation of researchers from the University of Michigan (Michigan) and University of Wisconsin-Madison (UW Madison). Each fiber is hundreds of times thinner than a strand of human hair. The fibers were then arranged into nanostructures that mimic the form and function of natural materials.

For example, the shape of a strand of polar bear fur traps heat from sunlight to help keep the animal warm in its freezing environments. It also lets light pass through it to make it look as white as snow.

Meanwhile, the broad leaves of the lotus are covered in waxy tubules that stop water from touching the surface of the plant. And the nanohairs on the soles of gecko feet tap the atomic forces of attraction so that the little reptiles can continue laughing at gravity.

The researchers believe their creations could one day serve as substitutes for the natural materials they are copying. (Related: Plant proteins used in new nanofiber dressing that accelerates healing and improves tissue regeneration.)

Researchers can now customize the properties of nanofiber carpets

The Michigan-UW Madison researchers tested the nanofibers for other abilities. In one experimental set-up, they were able to alter the optical properties of the material. The resulting structure displayed the ability to glow in the dark.

In another experiment, they also compared the ability of differently-shaped fibers to adhere to each other like Velcro. They found that clockwise and counterclockwise-curved nanofibers entwined together more tightly than the straight ones.

Ironically, the original objective of the joint project was to create a sensor with enough sensitivity to spot individual molecules. Instead, they accidentally developed a new approach to nanomaterials.

“The discovery reinforces my view that the best advances in science and engineering occur when things don’t go as planned,” explained Michigan researcher Nicholas Abbott. “You just have to be alert and view failed experiments as opportunities.”

Accidental discovery lead to scientific breakthrough

At the start of the experiment, the researchers put a small amount of polymer material onto liquid crystals. They vaporized single links in the polymer chains so that the evaporated material would condense as a thin film.

However, the polymer material did not always end up coating the top of the liquid crystal. The condensed links sometimes bypassed the crystal and reached the glass slide beneath the liquid.

These escapee polymers pooled together to form nanofibers. As they expanded upwards, the fibers followed the shape inadvertently set by the liquid crystals. The end result is a polymer carpet at the nanoscale level.

Abbott remarked on the disordered nature of a liquid crystal. However, the said liquid possessed more than enough stability to act as a mold for nanofibers. It could even set the specific diameter and length for the polymer formation.

The Michigan-UW Madison demonstrated the extent to which they could use the liquid crystal to customize the nanofibers. They used the same polymer material to make two mats with different levels of water repulsion.

One mat was merely hydrophobic. It forced water to bead on its surface. But the other one was superhydrophobic and sent the water moving away from its surface.

Furthermore, the researchers were able to make curved fibers just as easily as the straight ones. The liquid crystal made it very easy for them to shape the polymers into three-dimensional nanostructures.

Sources include:

Nanowerk.com

Science.ScienceMag.org