In the course of the FLOWTONICS ERC Starting grant project, we have reached all the objectives and milestones that we set in our initial proposal. Here I summarize the achievement following the structure of the proposed work plan:
Part 1: template dewetting of photonic structures
We have demonstrated for the first time the control over fluid instabilities of optical glass thin films to realize state-of-the-art nanophotonic structures over large area, soft and rigid substrates. We could model and experimentally demonstrate the self-assembly of a variety of optical nanostructures with feature sizes down to 10 nm (Figure 1a&b). We demonstrate this process on a variety of Chalcogenide glasses that can be used as optical waveguides, for their non-linear optical properties, their phase change and optoelectronic properties, as well as in sensing and metasurfaces (Figure 1c).
These achievements fulfill the objectives set in Part 1 of the project, and part 2.1. This study has led to one paper in Nature Nanotechnology presenting the science and potential of this novel ano-processing approach. We also published a second paper going more deeply into the fluid dynamic modeling in Physical Review Applied, and one in Nanophotonics demonstrating dewetted structures for nonlinear optics. IP is also being protected for this methodology.
Note that we also went beyond the original objectives of the proposal by applying these principles to liquid metals (Figure 1d&e). Two papers (Adv. Funct. Materials and Science Advances) came out of this approach where thanks to texturing we could control how liquid metal film can self-organize.
Part 2: Large area and flexible photonic nanostructures
The objectives regarding textured and nanowire based electronic and optoelectronic devices were tackled in two projects, that built upon the initial objectives but went beyond with an original fabrication of nanowires:
Sub-micrometer textured fibers:
We proposed a first original concept of combining soft nano-imprinting of thermoplastic plates with their thermal drawing. This work has led to a publication in Advanced Functional Materials (27, 1605935 (2017)) that received a lot of press, and presented in top international conferences. A patent was also submitted.
Nanowire-based optoelectronic fibers:
We have proposed a novel approach to grow nanowires not during thermal drawing but post-drawing. We demonstrated, for the first time, the integration of high quality single crystal semiconducting nanowire-based optoelectronic devices at the tip and along the length of polymer optical fibers.
This work led to a paper in Advanced Materials (29, 1700681 (2017)), and presented at several international conferences such as MRS, Spring Meeting 2017 and CLEO 2018.
Part 3: Nanostructured flexible and stretchable photonic fibers and ribbons
Part 3 proposed to expand the range of materials compatible with the thermal drawing to elastomers. Surprisingly, despite more than 50 years of exploitation of the thermal drawing process, it could never be applied to elastomers. We have been able to alleviate this limitation and demonstrate that some thermoplastic elastomers (TPEs) can be compatible with the multi-material thermal drawing process. We also identified functional materials such as thermoplastics, polymer nano-composites or liquid metals that can be co-drawn within such TPEs matrices in three-dimensional (3D) micro-structured architectures of unprecedented complexity. We showed examples of advanced fibers that can act as highly stretchable (up to 500 % strain) electronic or optical interconnects, or robust pressure or strain sensors, combining high performance and multiple embedded functionalities.
The results we obtained were published in Advanced Materials (30, 1707251 (2018)), which received a lot of press (see for example
https://actu.epfl.ch/news/an-elastic-fiber-set-to-revolutionize-smart-clothe/(odnośnik otworzy się w nowym oknie)). Several other papers resulted from this first studies, with novel pressure sensing fibers (Adv. Fucnt. Materials publication, Figure 2a to c)) and the first soft trnasmissionlines for sensing (paper in Nature Electronics, Figure 2 d to h). We also submitted a patent and received an ERC PoC proposal to further investigate the potential commercialization of this novel technology. As we explain in other part of this final report portal, this work has led to a partnership with a company to further exploit these novel fibers.
