Hydrogel materials have already been identified for use as smart bandages and as biocompatible tissue scaffolds. Now, researchers at the Massachusetts Institute of Technology (MIT) and Harvard Medical School (both in Cambridge, MA) have succeeded in developing hydrogel optical fibers that are not only flexible and stretchable, but have light-guiding properties that enable their use in biological sensing applications.
Composed of a hydrogel core and a polymer cladding, the hydrogel optical fibers at first suffered from separation of these two materials upon bending or stretching. To combat this issue, the researchers created a molecular-level glue by adding conjugation chemicals that linked carboxyl groups in the cladding and amine groups in the core. By injecting colored dyes into the fiber and measuring the output at various wavelengths as the fibers are stretched, an effective mechanical strain sensor is possible that could be implanted within a patient to monitor physical movement during therapy and inflammation, for example.
More recently, Harvard Medical School researchers have also developed hydrogel optical fibers functionalized with phenylboronic acid that experience reversible changes in the hydrogel fiber diameter in response to glucose. By analyzing the light propagation loss as a function of glucose concentration, these fibers could be used for quantitative glucose measurements within biological tissue. References: https://goo.gl/h5PihQ and https://goo.gl/ihBmAi.
