Article on Master’s thesis of former MAP student published as cover in ‘Advanced Functional Materials’

Picture courtesy of Andreas Leber / Advanced Functional Materials

Optical fibers, a widely employed tool for the transmission of light, are commonly made of rigid materials such as glass or thermoplastics. The mechanical properties of these materials prohibit the use of optical fibers in scenarios where large deformations are expected, such as wearable functional textiles.

In the framework of a transatlantic collaboration, researchers from Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) and Massachusetts Institute of Technology (MIT) led by professors Nicolas Vogel and Mathias Kolle, developed highly stretchable and flexible optical fibers made of thermoplastic elastomers. The lead author of the study, Andreas Leber, carried out the research during his MAP master’s thesis. The resulting work was recently published in the journal Advanced Functional Materials, where it was also featured on the inside back cover.

In the design of the optical fibers, which are capable of reversibly sustaining strains of up to 300% while guiding light, the scientist took advantage of the melt-processability of two thermoplastic elastomers and employed a coextrusion process to create the high index core – low index cladding structure of optical fibers at a scale of several hundred meters of fiber per hour. Moreover, they found that deformation of the fibers through stretching, bending, and indentation induces detectable, predictable, reversible, and wavelength-dependent changes in light transmission. Quantitative knowledge about the coupling of the fibers’ mechanical and optical properties forms the basis for the design of fiber-based sensors that are capable of reliably assessing extreme mechanical stimuli. The researchers went on to demonstrate the fibers’ utility in sensing scenarios by integrating them in a knee brace for continuous knee motion tracking, a glove for control of a virtual hand model, and a tennis racket capable of locating ball impacts. Such devices can greatly improve quantitative assessment of human motion in rehabilitation, sports, human-machine interaction and anywhere else where large deformations need to be monitored reliably.