Bio-mimicry of polar bear fur offers insulation

Inspired by the microstructure of polar bear hairsand how they provide heat insulation in an inhospitable environment, Chinese researchers have developed an insulator that reproduces the structure of individual hairs in a synthetic material. As the properties of polar bear hair work to prevent heat loss, they are a useful model for a synthetic heat insulator, and this new material mimics the structure of polar bear hairs to lock in heat in the same way, in a development that could find useful applications in architecture and aerospace.

The hair from polar bears are hollow and waterproof, with each having a long, cylindrical core directly through its center. It is the shape and spacing of such narrow cavities that provides their unique heat-holding capacity and water resistance, as well as stretchiness, characteristics that are essential for a thermal insulator. As reported in the journal Chem [Zhan et al. Chem (2019) DOI: 10.1016/j.chempr.2019.04.025], to both mimic and scale the hairs for practical purposes, researchers fabricated a carbon tube aerogel (CTA), a microstructure-derived material that shows excellent thermal insulation property and is lightweight, waterproof and thermally insulating, as well as being mechanically stable and chemically inert.

Millions of hollowed-out carbon tubes were produced that were equivalent to a single hair, before winding them into an aerogel block. By making tube aerogel out of carbon tubes, an analogous elastic and lightweight material was designed that traps heat without degrading hugely over its lifetime. As well as being lighter, non-wettable and offering greater resistance to heat flow than other aerogels and insulation components, the hollow-tube design displayed even greater stretchiness than polar bear hairs, providing useful engineering applicability and super-elasticity.

In addition, the hollow structure of the fibers helps to reduce thermal conductivity as the inner diameter of carbon tube fibers is lower than the mean free path of air. As co-senior author Shu-Hong Yu, from the University of Science and Technology of China, told Materials Today, “The lightweight, water-proof and excellent thermal insulating and mechanical properties of the biomimetic carbon tube materials are ascribed to ingenious hollow structure bio-inspired by the polar bear hair”.

The team now hope to explore ways of scaling up the fabrication process to produce insulators on the meter rather than centimeter scale, and to identify potential industrial uses. Although the material currently cannot be easily mass produced, they expect such size limitations can be overcome, perhaps for key aerospace applications.

“The lightweight, water-proof and excellent thermal insulating and mechanical properties of the biomimetic carbon tube materials are ascribed to ingenious hollow structure bio-inspired by the polar bear hair”Shu-Hong Yu

Inspired by the microstructure of polar bear hairsand how they provide heat insulation in an inhospitable environment, Chinese researchers have developed an insulator that reproduces the structure of individual hairs in a synthetic material. As the properties of polar bear hair work to prevent heat loss, they are a useful model for a synthetic heat insulator, and this new material mimics the structure of polar bear hairs to lock in heat in the same way, in a development that could find useful applications in architecture and aerospace.

The hair from polar bears are hollow and waterproof, with each having a long, cylindrical core directly through its center. It is the shape and spacing of such narrow cavities that provides their unique heat-holding capacity and water resistance, as well as stretchiness, characteristics that are essential for a thermal insulator. As reported in the journal Chem [Zhan et al. Chem (2019) DOI: 10.1016/j.chempr.2019.04.025], to both mimic and scale the hairs for practical purposes, researchers fabricated a carbon tube aerogel (CTA), a microstructure-derived material that shows excellent thermal insulation property and is lightweight, waterproof and thermally insulating, as well as being mechanically stable and chemically inert.

Millions of hollowed-out carbon tubes were produced that were equivalent to a single hair, before winding them into an aerogel block. By making tube aerogel out of carbon tubes, an analogous elastic and lightweight material was designed that traps heat without degrading hugely over its lifetime. As well as being lighter, non-wettable and offering greater resistance to heat flow than other aerogels and insulation components, the hollow-tube design displayed even greater stretchiness than polar bear hairs, providing useful engineering applicability and super-elasticity.

In addition, the hollow structure of the fibers helps to reduce thermal conductivity as the inner diameter of carbon tube fibers is lower than the mean free path of air. As co-senior author Shu-Hong Yu, from the University of Science and Technology of China, told Materials Today, “The lightweight, water-proof and excellent thermal insulating and mechanical properties of the biomimetic carbon tube materials are ascribed to ingenious hollow structure bio-inspired by the polar bear hair”.

The team now hope to explore ways of scaling up the fabrication process to produce insulators on the meter rather than centimeter scale, and to identify potential industrial uses. Although the material currently cannot be easily mass produced, they expect such size limitations can be overcome, perhaps for key aerospace applications.