Séminaire IUSTI – 03 septembre 2021 – 11h salle 259

Building with fluids, lazy design of functional materials

Pierre-Thomas Brun – Princeton Univ, ÉU

From acoustics to optics, electronics and mechanics, the need for structured materials is well established. Examples include lightweight structural materials, photonics and phononic materials, super-hydrophobic materials and mechanical metamaterials. Despite the recent progress of 3D printing, the fabrication of such structures spanning a wide range of sizes remains difficult or impossible, prompting the development of new fabrication pathways. The work I will present is concerned with the directed control of mechanical instabilities to program shapes. While instabilities are traditionally regarded as a route towards failure in engineering, I aim to follow a different path; taming instabilities and harnessing the patterns and structures they naturally form to fabricate functional materials. This methodology capitalizes on the inherent periodicity, scalability, versatility and robustness of instabilities. This new design paradigm – building with instabilities – calls for an improved understanding of instabilities and pattern formation in complex media. While stability analysis is a classic topic in mechanics, little is known on the so called inverse problem: finding the optimal set of initial conditions and interactions that will be transmuted into a target shape without direct external intervention. Three examples will be presented: (1) a fluid-instability based approach for digitally fabricating geometrically complex uniformly sized structures, (2) the rapid fabrication of nearly uniform hemispherical elastic shells by drainage and (3) their pneumatic actuation towards shape morphing applications.