MIT researchers develop flexible optical fibre for medical implants in the brain

A collaboration of researchers between Massachusetts Institute of Technology (MIT) and Harvard Medical School has resulted in the development of highly flexible and stretchable optical fibre for use in biomedical implants within the human body. The fibre can be used to measure strain, detect signs of disease, or directly treat cells in the human body, especially in the brain. The optical fibre is based on hydrogel, a material made up mostly out of water. The implants are long lasting and can remain within the human body for extended periods of time. One of the major use case scenario is in a field of medical science known as optogenetics. Here, pulses of light are used to directly activate cells, especially neurons in the human brain. Very thin needle like fibers are used for this purpose. The brain is made up of jelly like material that can be easily damaged by stiff optical fibers. The flexible fiber can allow for therapy over longer durations of time. Xuanhe Zhao, the Robert N. Noyce Career Development Associate Professor in MIT’s Department of Mechanical Engineering says, “The brain is like a bowl of Jell-O, whereas these fibers are like glass — very rigid, which can possibly damage brain tissues. If these fibers could match the flexibility and softness of the brain, they could provide long-term more effective stimulation and therapy.” Previously, the bio-optics group at Harvard Medical School had developed hydrogel based optical fibers for this purpose. However, these fibers would snap when stretched or bent. The team from MIT collaborated with the team from Harvard, to try out various recipes for improving the fiber. A design was jointly developed that allows the fibers to stretch over seven times their original length, without any fading away of the light being transmitted. Apart from brain implants, there are other use cases for the newly developed fibers. If the fiber is filled with dyes of various colours along the length, and implanted within limbs, medical professionals can analyse light shown through the fibers for signs of improvement or deterioration in the condition of the limb under treatment. As the fiber stretches or contracts in different regions, the signature of the light that emerges changes. Another use case is the embedded fiber in the human body lights up like a notification beacon at the signs of disease.