Scientists at EPFL were able to use their novel imprinted fibers to guide neurites from a spinal ganglion (on the spinal nerve). Image: EPFL.
Scientists at EPFL were able to use their novel imprinted fibers to guide neurites from a spinal ganglion (on the spinal nerve). Image: EPFL.

Researchers at Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland have come up with a simple and innovative technique for drawing or imprinting complex, nanometric patterns on hollow polymer fibers. They report this work in a paper in Advanced Functional Materials.

The potential applications of this breakthrough are numerous. The imprinted designs could be used to impart certain optical effects on a fiber or to make it water-resistant. They could also guide stem-cell growth in textured fiber channels or be used to break down the fiber at a specific location and point in time in order to release drugs as part of a smart bandage.

To make their nanometric imprints, the researchers began with a technique called thermal drawing, which is commonly used to fabricate optical fibers. Thermal drawing involves engraving or imprinting millimeter-sized patterns on a preform, which is a macroscopic version of the target fiber. The imprinted preform is then heated to change its viscosity, stretched like molten plastic into a long, thin fiber and allowed to harden again.

Stretching causes the pattern to shrink while maintaining its proportions and positioning. Yet this method has a major shortcoming: the pattern does not remain intact below the micrometer scale. "When the fiber is stretched, the surface tension of the structured polymer causes the pattern to deform and even disappear below a certain size, around several microns," said Fabien Sorin, head of EPFL's Laboratory of Photonic Materials and Fibre Devices.

To avoid this problem, the EPFL researchers came up with the idea of sandwiching the imprinted preform in a sacrificial polymer. This polymer protects the pattern during stretching by reducing the surface tension, and is discarded once the stretching is complete. Thanks to this trick, the researchers were able to imprint tiny and highly complex patterns on various types of fibers.

"We have achieved 300nm patterns, but we could easily make them as small as several tens of nanometers," said Sorin. This is the first time that such minute and highly complex patterns have been imprinted on flexible fibers on a very large scale. "This technique enables us to achieve textures with feature sizes two orders of magnitude smaller than previously reported," said Sorin. "It could be applied to kilometers of fibers at a highly reasonable cost."

To highlight potential applications of their achievement, the researchers teamed up with colleagues at EPFL’s Laboratory for Soft Bioelectronic Interfaces. Working in vitro, they were able to use the imprinted fibers to guide neurites from a spinal ganglion (on the spinal nerve). This was an encouraging first step toward using these fibers to help nerves regenerate or to create artificial tissue.

This development could have implications in many other fields besides biology. "Fibers that are rendered water-resistant by the pattern could be used to make clothes. Or we could give the fibers special optical effects for design or detection purposes. There is also much to be done with the many new microfluidic systems out there," said Sorin. The next step for the researchers will be to join forces with other EPFL labs on initiatives such as studying in vivo nerve regeneration.

This story is adapted from material from EPFL, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.