Viscous Flow Engineering: a Novel Approach for the Scalable Fabrication of Advanced Multi-material Fibers and Metasurfaces

The dewetting of thin polymeric films and the thermal drawing of polymer and glass fibers are two seemingly very different processes. They can however both be described for a large part via an interplay between viscosity and surface tension [1]. In this talk, we will first show how we can control the solid-state dewetting of thin, high refractive index optical glass layers onto patterned polymer substrates to realize high–quality optical metasurfaces. We will investigate how the interplay between viscous flow at the nanoscale and surface tension enables to tailor the size and shape of chaclogenide glasses nano-objects and hence control their optical properties. Second, we will present how we can apply similar principles to the process of thermal drawing – the same process used to fabricate optical fibers – to realize multi-material fibers and ribbons with advanced optical and electronic functionalities [2]. In particular, we will show how we can fabricate thin and flexible fibers with sub-micrometer surface patterns by tailoring the materials surface tension. We will then demonstrate how applying this understanding to electrically conducting polymer nano-composites can lead to intriguing fiber devices such as electromechanical one-dimensional distributed touch sensors [3]. Turning to semiconductor-based fibers, we will show how modifying the surface energy of semiconducting materials in solution can enable the fabrication of single-crystal nanowire-based optoelectronic fibers with unprecedented performance [4]. Finally, we propose for the first time to tailor the viscosity of materials during thermal drawing by looking at rheological and microstructural attributes at a deeper level. We will in particular show how we could identify some elastomeric materials that can be drawn with flow properties similar to their thermoplastic counterparts. This opens novel opportunities for fiber-based devices in the fields of stretchable optics and electronics as well as biological probes and smart textiles.

References
[1] M. Schmidt et al. Advanced Optical Materials, 2016, 4, 13.
[2] T. Nguyen et al. Advanced Functional Materials, 2017, 27, 1605935.
[3] T. Nguyen et al. J. of Physics D: Appl. Phys., 2017, 50, 144001.
[4] W. Yan et al, Advanced Materials, 2017, 29, 1700681.
About the research of the speaker: https://fimap.epfl.ch