What do the most basic t-shirts have in common with cutting-edge fabric that can detect and neutralize nerve gas? The answer is cotton, “the fabric of our lives” as it’s called by the U.S. industry. Cotton is one of the most promising fabrics for applications in wearable “smart materials”, such as clothing that responds to changes in temperature, harnesses motion to power electronics, is highly-visible, or monitors body functions.
Creating smart materials requires instilling cotton or similar fabrics with properties they don’t come by naturally, such as the ability to conduct electricity. Traditionally, these properties are added to a fabric via chemical treatments. However, chemical treatments can turn a soft, comfortable shirt into one that feels rough and irritates the skin. In addition, properties added by chemical treatments are susceptible to washing and wearing away.
Today in the AAAS journal Science, an international team of scientists discusses another method for instilling desired properties into cotton—one that requires no chemical treatments. In this work, led by Filipe Natalio from Martin Luther University of Halle-Wittenberg in Germany and the Weizmann Institute of Science in Israel, scientists actually grew cotton with fibers that had fluorescent properties and magnetic properties without genetically modifying them.
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| This microscopic image taken under ultraviolet light shows fluorescing cotton. Image Credit: Filipe Natalio. |
A few months after farmers plant cotton seeds, cotton plants produce flower buds. Within a matter of a few weeks, the buds open, wither, and then fall, leaving behind pods. The cotton fibers that you’re probably familiar with grow out from ovules in these pods and eventually split the pods apart, revealing their fluffy, white insides.
The first step in this process was observing chemistry at work. The researchers studied the path by which water-soluble molecules were absorbed by ovules and transported to their outer layers to be metabolized and integrated into growing fibers. They did this using different kinds of pigments. One type of pigment was a derivative of glucose—the sugars created during photosynthesis, while the other contained no glucose. By examining the color of the ovules and their cotton fibers after 20 days, the researchers figured out a kind of recipe for a chemical compound that could take fluorescent molecules (or other “functional” molecules) up through the plant to be metabolized and integrated into the cotton fibers.
Glucose turned out to be a key ingredient, so the researchers designed and synthesized a glucose derivative for carrying a fluorescent chemical ingredient through the pathway. They incubated fertilized ovules, put them in contact with the glucose derivative, and photographed the cotton fibers as they developed over the course of 20 days. After 20 days, the fibers glowed a bright green under ultraviolet light while a control group (with no fluorescent ingredient) did not fluoresce at all.
The researchers then repeated this process, but replaced the fluorescent ingredient with one designed to instill magnetic properties in the cotton fibers. After 20 days, to the naked eye the fibers looked identical to those in a control group, but an in-depth analysis revealed that magnetic properties had indeed been biologically incorporated into the fibers.
This proof-of-concept study demonstrates that with an appropriate chemical recipe, you can grow cotton fibers with desirable properties—an approach that may be preferable to chemical coatings for lots of applications. Furthermore, say the authors, this approach isn’t necessarily limited to cotton. They suggest that it could work for materials like bamboo, silk, flax, and even bacteria. Just imagine the possibilities! If you need some help imagining, check out the team’s video below for a taste.
PS: If you like this story, you’ll probably be interested in what happens when researchers feed graphene to spiders. Unfortunately, we didn’t get a chance to cover it for Physics Buzz, but you can check it out here, Tough stuff: Spider silk enhanced with graphene-based materials.