Once a porcupine’s quill penetrates your skin, it’s very difficult to remove. That’s the inspiration behind research at Massachusetts Institute of Technology and Brigham and Women’s Hospital, Boston, to develop new types of adhesives, needles, and other medical devices.

Fig. 1 – Porcupine photographed by Mary Harrsch.
In a new study, researchers characterized the forces needed for quills to enter and exit the skin. They also created artificial devices with the same mechanical features as quills, raising the possibility of designing less-painful needles, or adhesives that can bind internal tissues more securely.

North American porcupines, as seen in Figure 1, have about 30,000 barbed quills, each several centimeters long, and the four millimeters at the very tip are covered in microscopic barbs. To their surprise, the researchers found that, despite the difficulty of removing the quills, they require very little force to penetrate tissue. The team then set out to determine how the quills achieve this unique combination and discovered that the barbs are the key to both.

To explore the possibility of making stronger adhesives, the researchers created a patch with an array of barbed quills on one side. (See Figure 2) They found that the energy required to remove this patch was 30 times greater than that needed for a control patch with quills, but no barbs.

There is a great need for such adhesives, especially for patients who have undergone gastric-bypass surgery or other types of gastric or intestinal surgery, according to the researchers. These surgical incisions are now sealed with sutures or staples, which can leak and cause complications.

Fig. 2 – This fluorescent microscope image shows the tiny barbs that coat the tip of a porcupine's quills. (Credit: Woo Kyung Cho)
“With further research, biomaterials modeled based on porcupine quills could provide a new class of adhesive materials,” says Robert Langer, the David H. Koch Institute Professor at MIT and a senior author of the study, which appeared in the Proceedings of the National Academy of Sciences. The system could also be tweaked so that it penetrates tissue easily but is not as difficult to remove as a porcupine quill, enabling design of less-painful needles for injections. The researchers are now working on making quill-inspired adhesives from biodegradable materials, which could be broken down inside the body after they are no longer needed.

The research was funded by the National Institutes of Health, the American Heart Association, the National Science Foundation and the National Research Foundation of Korea.