Professor René Wasserman Award - 2022 - Inès Richard
Ultimate feature sizes in thermally drawn fibers: from fundamental analysis to functional fibers
EPFL thesis n°8455
Thesis director: Prof. F. Sorin
For her remarkable contributions, both in fundamental understanding and applied research, in the thermal drawing of polymers and metallic glasses.
The fiber thermal drawing process has emerged as a simple and scalable technique for the fabrication of multifunctional and flexible electronics. However, the trend of increasing number of functionalities, which requires a reduction in size of each component, revealed the importance of instability mechanisms, which are the core of this thesis.
We first focus on the thermal reflow of polymeric textures and develop a model to predict it evolutions during processing. We show that the reflow driving force can be significantly reduced by codrawing two materials of low interfacial tension. We then study the polymer chain alignment induced by thermal drawing. Our understanding enables us to control the shrinkage behavior and tune the mechanical properties and bending behavior of multi-material fibers. We finally tackle the long-lasting challenge of drawing bulk metallic glasses (BMGs) which enable us to circumvent the size limitation of crystalline metal electrodes due to capillary instabilities. We demonstrate the production of well-ordered BMG ribbons of thicknesses down to 40 nm and demonstrate an increase in crystallization kinetics with an increase in deformation and decrease in size. We then develop novel neural probes allowing electrical stimulation, recording and precise drug delivery, and all-in-fiber electrochemical sensors.