Nanofibers have recently been utilized in many applications, ranging from wound dressings to air filters to high-strength composite materials. Scientists have now developed a faster and simpler method of producing those fibers, which was inspired by the silkworm.
According to researchers from China's Sichuan University, existing nanofiber production methods such as electrospinning are all either complicated, slow, or result in clumpy fibers.
By contrast, the silkworm produces its own high-quality ultra-thin silk fibers quickly and easily. It does so simply by secreting its sticky saliva onto a surface and then pulling its head back, drawing the saliva into a long thread. The Sichuan researchers have replicated that process, in a technique known as microadhesion-guided (MAG) spinning.
It involves pushing an array of microneedles into a piece of foam soaked with a polyethylene oxide solution, then pulling them back out again. As the needles are withdrawn, each one pulls a thin thread of the polymer out of the sponge. Those threads dry quickly, at which point they can be cut and put to use.
What's more, by mimicking the different ways in which the silkworm moves its head when producing its silk fibers, it's likewise possible to create different sorts of nanofibers via the MAG spinning technique.
For instance, if the needles are simply pulled straight back from the sponge, the fibers are all straight and aligned. If the needle array is swayed or vibrated, however, the fibers cross-link with one another. And if the array is turned to one side or the other as it's being pulled back, the nanofibers all twist together to form a single larger fiber.
In fact, depending on the type of nanofibers required, it was found that the microneedle array isn't always necessary.
Simply by placing two polymer-soaked sponges together then pulling them apart, the scientists were able to produce straight nanofibers which were used to create an instant bandage that was placed on a person's skin. As an added bonus, an antibiotic that had been added to the polymer allowed the bandage to inhibit the growth of harmful bacteria.
A paper on the research – which was led by Yu Wang, Wei Yang and Xuewei Fu – was recently published in the journal Nano Letters. The MAG spinning process is demonstrated in the video below.
Source: American Chemical Society
