Studying Threads Intricately Complex Hydrodynamics

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When knitting meets fluid dynamics. Knitting generates fabrics by meticulously guiding yarn into interlocking loops and stitches. Inspired by the legacy of this ancient craft, we propose to study the formation and deformation of complex entangled assemblies “stitched” by the liquid rope coiling instability. We will study the periodic stichlike patterns forming when a viscous thread falls and buckles onto a moving substrate, such as the coils created when honey is poured onto toast. Here, we focus on the case of solidifying liquids that “freeze” the patterns formed by these flows into structured solids. In turn, these structures can be leveraged to achieve tunable mechanical properties. This approach is an instability-augmented version of 3D printing where fluid dynamics co-fabricates the parts, e.g., by coiling and layering fused thermoplastics filaments. Despite their singular potential for materials’ design and fabrication, our understanding of these complex flows remains sparse, leaving outstanding scientific questions unanswered. STITCH will fill this gap of knowledge and elucidate the intricate relation between flow, form, and function. We will integrate rigorous experimentation and modelling techniques to rationalize how our liquid patterns fuse into resilient solid composite materials. This deeper understanding will allow us to tame instabilities in solidifying melts, serving as the foundation for engineering precisely crafted architected solids across length scales, potentially impacting diverse sectors, from tissue engineering to construction. We will leverage our findings to push innovative frontiers in manufacturing with the ambitious and high-risk goal of developing aerial printing methodologies, where one or more drones work together to build from the sky. Our fundamental work is dedicated to materializing this nascent paradigm, bringing it from the realm of science fiction into concrete reality.