Painless Micro-Needles İnspired by Mosquitoes
Learn from nature to develop really painless syringes. And what better model of the mosquito?
This insect succeeds in inserting its needle-like probe into the skin and sucking the blood for several minutes, without the victim noticing it. That’s why the Ohio State University researchers took inspiration from the mosquito to design a new painless micro-needle for medical purposes. An instrument that will be composed, in fact, of two needles: one ‘classic’ and the other serrated one.
“Mosquitoes must do something right if they can puncture our skin and suck blood without causing pain,” reflects Bharat Bhushan, a mechanical engineering professor at Ohio State University. “We can use what we learned from mosquitoes as a starting point to create a better micro-needle.”
In a study published in the Journal of Mechanical Behavior of Biomedical Materials, the US team analyzed the mosquito, discovering the four elements that allow it to “strike” without causing pain: the use of a paralyzing agent; a serrated needle design; a vibration during the puncture; the combination of soft and hard parts on the ‘proboscis’. “We can incorporate all these elements into a new micro-needle,” Bhushan said. “Currently, the needles are very simple, there has not been much innovation, we think it’s possible to try something different”.
In their work, the researchers analyzed the outer cover of the proboscis, called labrum, of females of Aedes vexan, the most common mosquito in North America. Thanks to a special technique the team has tested the hardness and rigidity of the labrum in seven different points. Discovering that the ‘stiletto’ was softer near the tip and edges and stiffer and harder inside and above the labrum. “This is important because a softer, more adaptable tip and can cause less pain when it pierces the skin, since it deforms it less,” explains Bhushan.
This is one of the four keys to painless puncture, according to the researchers. Not only. The part that sucks blood – fascicle, has a serrated design, just like a miniature saw. It may seem painful, but instead it is useful because it facilitates the insertion, moreover this element vibrates when it is inserted, which also helps to reduce the force necessary to pierce the skin. Other research has shown that mosquitoes use a force three times lower than the lowest one needed for an artificial needle.
Finally there is the use of a paralyzing agent: once inserted the proboscis, the insect releases saliva, which contains a protein that reduces pain. Based on these results, Bhushan imagines a micro needle with two needles inside: one would immediately inject a paralyzing agent, while the second needle would ‘suck’ the blood or inject the drug. This second needle would have a notched design and would be more flexible and softer on the tip and sides. Vibrating at the time of insertion. A solution certainly more expensive than traditional needles, but that could be useful for children or adults terrified at the idea of an injection. “We have the materials and the knowledge to create a micro-needle like this”, assures Bhushan. “The next step is to find financial support to build and test such a device”.