Wild silk moth inspires researchers to weave smart fibers with integrated cooling
Although human civilization has managed to create a technophilic planet, the pristine nature would always be the best resource to learn from. Even in the age of smart products, nature is one of the few things that is still a mystery to our kinds and holds the key to all the future developments. Without any further ado, let us know what a group of researchers at the Columbia University, School of Engineering and Applied Sciences has discovered from the comet moth's cocoon fibers.
As the official publication suggests, the group was in search of some optical properties unique to the Madagascar comet moth's cocoon fibers when the team found out about its exceptional capabilities to reflect sunlight and to transmit optical signals and images. Since ancient times, the silk moth fiber has generated a significant amount of interest among fashionistas and business tycoons, harboring a huge profit from textile industries. In the research world, the scenario is not much different. The fabrics from Silkworm is famous in the scientific community for its luster and cooling properties. This time, the group discovered a wild silk moth, the Madagascar comet moth (Argema mittrei) produces a type of fiber that possesses exceptional cooling abilities with enhanced capabilities to transmit optical signal and images.
The team leader Nanfang Yu, associate professor of applied physics has mentioned that the optical properties connected to the one-dimensional nanostructure present in the fiber have immediate importance in contemporary applications. Waiting no more, the team jumped right into fabricating the fiber which mimics the internal nanostructure and optical properties of the natural fiber. An expert in nanophotonics, he further added that the wild silkmoth fiber is one of the best natural fibrous material available to block sunlight which may create its demand in fiber industry. Also, due to its light channeling property this can also be implemented as biocompatible and bioresorbable material for optical signal and image transport in biomedical applications.
In comparison to solid, transparent and cylindrical regular silkworm fiber the comet moth fiber appears to bear a metallic sheen. Under an optical microscope, the structure has shown a high density of nanoscale filamentary air voids that goes beneath the fibers like pipelines under roads and cause mirror-like reflection of light. When it comes to reflectivity, a single comet moth fiber layer can be equated to ten transparent layers of a domesticated moth fiber. Plus it can also reflect infrared rays, invisible to human eyes, storing half of the solar power. Combined with its skill to absorb ultraviolet (UV) light, this fiber has been proved to be ideal in blocking sunlight.
In addition to this, the light guiding effect produced by the moth fibers is an example of transverse Anderson localization and is caused by the filamentary air voids along the fibers which help in optical scattering in the fiber cross-section, confining the light in sideways but involving no hindrance for light propagation along the fibers. The phenomenon used is much different from the conventional method inside a fiber-optic cable where light confinement is provided by the total internal reflection between the core and cladding layer.
The other part of the experiment was to derive a novel fiber pulling method that emulates the fiber spinning mechanism of the comet moth by inserting high-density filamentary voids, much greater than what nature put in their plates. The bioinspired fiber is made up of two types of fibers namely a regenerated silk i.e., a liquid precursor of silk fibers and polyvinylidene difluoride, a type of synthetic polymer that gives a reflectivity of 93% ( in comparison to comet moth fiber's 70%).
Interestingly, the team explained that the biggest difference between the scientifically generated fiber and the silk fiber used in textiles is the core which is made up of nanostructures for the first one. However, more importantly, they hope to revolutionize the textile industry by embedding novel optical and thermodynamic functions into fibers and textiles. Yes, these type of fibers can weave ultra-thin summer clothing with a cooling effect.
A few layers of fibers can make an opaque sheet of textile that will have a fraction of a sheet of paper in thickness. However, it won't be translucent with the wearer's perspiration, one of the common problems faced in today's garments. Unlike conventional fiber, which becomes transparent due to reduced fiber-air interfaces, the nanoscale air voids embedded in the bioinspired fibers will not allow that. Plus, the smart clothes will exert cooling by combining sweat evaporation, air flow between the microenvironment of the human body and the exterior, and radiation of body heat to the environment. That is how the wearer will experience an ultimate cooling sensation due to the compound effect of evaporative, convective, and radiative cooling.
How did the Comet moth come into Professor Yu's attention? The journey is exquisite. The Madagascar Comet moth is one of the biggest in size with cocoons spanning 6 to 10 cm in length. The cocoons are built on the tree canopy of Madagascar that is exposed to intense sunlight. It is probably due to the natural selection that they possess a metallic sheen to protect the pupae from overheating. Brought to Professor Yu by Catherine Craig, director of the NGO Conservation through Poverty Alleviation, International.
Professor Yu's team is now concentrating on increasing the throughput of producing bioinspired fibers using the existing technology with as fewer modifications as possible. The article has been published in the Light Science and Applications Journal.