Imitating nature offers sustainable choices in new textiles.
Nature provides the inspiration for many innovations, including in the field of textiles. Some efforts, however, are quite specific in imitating nature. In fact, an entire field of science has blossomed under the name “biomimetics,” a term first coined in 1969 by Dr. Otto Schmitt, who spent much of his career as a professor and researcher at the University of Minnesota. Since then, the field has grown with many commercially successful products such as the Nanotex technology. Biomimicry has enabled the development of functional finishes, soft materials, textile technologies, binders and other products.
What is biomimetics?
As Yogi Berra is credited with saying, “You can observe a lot by just watching.” Biomimetics is all about observing and trying to mimic nature in order to develop value-added finishes and products, such as water-repellant coatings and improved adhesives, as examples. Biomimicry involves understanding how nature adapts and borrowing those underlying principles to develop value-added and functional products and processes.
Many discoveries and inventions in physical, engineering and biological sciences have stemmed from observing nature. Biologist Osamu Shimomura, who won the 2008 Nobel Prize in Chemistry discovered the green fluorescent protein (GFP) in jellyfish, Aequorea victoria, which is an important biological tool these days, supporting research in cancer and HIV, for instance.
There seems to be a symbiotic relationship between biomimetics and nanoscience. One of the early commercial successes with the application of nanoscience in textiles was based on bio-inspiration.
In 1998, Nanotex was founded based on the inspiration from nature in repelling water from a surface. This technology copied nature’s process using nanotechnology. Nano molecules bonded to textiles provided an efficient stain-repellant mechanism that resulted in magic stain removals, which caught the attention of retail brands and consumers. Today, Nanotex is part of Crypton Inc., and the nature-inspired Nanotex technologies are used in over 100 brands around the world.
Since the late 1980s, there have been tremendous efforts globally to develop nanofibers for a variety of applications from filtration to tissue scaffolds. As nanofibers are submicron-sized fibers, they provide high surface area. Also, additional characteristics that mimic nature, such as three-dimensional (3-D) structures and self-assembly, are important for using nanofibers for growing cells.
According to biotechnologist, Dr. Uday Turaga of Texas Tech University, “Everything inside the body is three dimensional and at macromolecular level, the extra cellular matrix is 3-D and nanofibers simulate the 3-D structure, which cells face in vivo.”
Despite the established protocols associated with growing cells on petri dishes, which are two dimensional (2-D), Turaga says these 2-D structures do not mimic the condition in vivo. In these circumstances, nanofiber meshes provide practical advantages. Turaga has been working extensively in the recent past to develop environmentally friendly nanowebs using biocompatible polymers such as ploy (vinyl alcohol).
These nanowebs are functionalized with natural antimicrobial products (for example, honey!) for developing value-added products such as wound dressings. Poly (vinyl alcohol) bandages with safe antiseptics, such polyhexamethylene biguanides, showed excellent antibacterial efficacies against Gram-positive and Gram-negative bacteria, according to Turaga.
The growth of biotextiles
The field of using natural products to impart functionality to textiles is growing. This field can be conveniently called “biotextiles.” Coimbatore, India-based Avinashilingam Institute for Home Science and Higher Education for Women (Avinashilingam Institute) has been a pioneer in the field of biotextiles. Professor Vasugi Raaja, Dean of Home Science at the institute says that the institute is one-of-a-kind in offering a post-graduate course in biotextiles. The program began accepting students in 2005.
Courses in the program focus on the theoretically practical aspects of utilizing natural products’ chemistry, such as enzymes and herbs, to impart functionalities to textiles. For more than a decade this institute has worked on interesting projects says Dr. Kalaiarasi, assistant professor of biotextiles. Amylase enzymes were isolated from bacterial and fungal species such as Bacillus cereus and Aspergillus. Papaya leaves have been used to extract protease enzymes, which can be used for degumming silk. Natural byproducts are used for effluent treatments, such as the decolorization of reactive dyes.
The textile dyeing and finishing industry would definitely benefit from such environmentally benign treatment technologies. Natural dyes are developed from natural products using ultrasonic processes, so that extraction becomes efficient. Dr. Prabha, assistant professor at Avinashilingam Institute, who has undertaken her dissertation research on using natural herbs to impart antimicrobial characteristics to textiles, says that the raw material is cost effective, so if the processes are optimized, these alternative treatments will be environmentally friendly and commercially viable.
Her project extracted flavonoids from natural products, such as Vetiveria zizanioides roots and Phyllanthus niruri leaves to impart mosquito repellency to cotton fabrics. In addition to utilizing natural products, the project utilized emerging environmentally benign processes such as plasma to improve the process efficiency and the durability of treatments.
The watch list
A team of multidisciplinary researchers at Stanford University, Calif., has developed a skin-like fabric that cools the body more efficiently. The use of nanoporous polyethylene fabric resulted in the lowering of skin temperature by about 2.7 degrees Centigrade when compared with another commonly used next-to-skin fabric. According to Yi Cui, associate professor of materials science at Stanford, the fabric effectively cools the person, which makes cooling the building unnecessary, thereby saving energy.
Scientists at Uppsala University, Sweden, in collaboration with German virologists have developed cellulose nanofiber sheets to remove viruses from water. Nanocellulose filter paper, termed mille-feuille filter because they have a layered structure resembling the French pastry mille-feuille, will be able to remove even small-sized viruses. These new, structured nanocellulose sheets are affordable filters that not only can remove viruses but also can have long life, according to Uppsala University. Compared to tea bag kind of cellulose filter, these French pastry-like filters have pore structures that can filter viruses that are normally resistant to physical and chemical countermeasure processes.
The Uppsala team, led by professor Albert Mihranyan, collaborated with virologists from Charles River Biopharmaceutical Services, Cologne, Germany. According to Mihranyan, their goal is to develop filter paper that can remove viruses from water as easily as brewing coffee.
Another team of scientists and students at Imperial College, London, has engineered bacteria found in green tea to produce cellulose that can find applications in filtration and the textile industry. The team has developed DNA tools to engineer a specific strain of bacteria found in fermented green tea to produce modified bacterial cellulose. This technique also enables incorporating proteins and other biomolecules into the bacteria.
Among many potential applications, protein-incorporated bacterial cellulose filters can be used to target contaminants in water supplies. An interesting application is the development of sensors using cellulose material that can detect biotoxins based on color change.
Biomimetic textiles are an exciting and emerging field within the high-performance and functional textiles category, and as an interdisciplinary field, it deserves due attention from the smart fabrics sector, as well.
With the need to use environmentally friendly products and processes, drawing inspiration from nature is indeed a good idea to develop products, such as waterproof materials, nature-inspired biocidal substrates and biomimetic adhesives.
As it is clear from the commercial successes of products such as Nanotex, technology, practical applicability and cost have to work in harmony to achieve this. Dr. Prabha of Coimbatore echoes this premise; in the case of natural products, they can be cheaper if they are available adequately, such as those she had used in India.
In addition to the cost advantages of using natural products, other important aspects are product durability and applicability. The ease of adapting nature’s ways and the durability of bioinspired products pose definite challenges for the next-generation textile industry, whether the field is biomimetic textiles, wearable textiles or some other market area.
Seshadri Ramkumar is professor of technical textiles, Texas Tech University.