Mechanical and Civil Engineering Seminar

Mechanical and Civil Engineering Seminar Series

Title: From folding to scaling: a tour through nonlinear mechanics

Abstract: Origami, the art of folding paper into intricate shapes, has growing practical applications across fields such as architectural design, therapeutics, deployable space structures, antenna design, and soft robotics. One promising yet largely unexplored area is curved tile origami, which can store elastic energy, offering opportunities to develop next-generation functional materials, structures, and actuators. In the first part of my talk I will present a general theory of curved origami and systematic design methods for constructing large-scale, complex curved origami structures. Additionally, I will present methods to accurately calculate the stored elastic energy and the folding motions of curved origami, and I will illustrate my theoretical results by presenting some complex structures I have folded. This theory has inspired applications of curved origami in fields ranging from medical devices to a vertical-axis wind turbine, to architected materials. These applications typically involve interacting fluids, highly deformable elastic solids and rigid bodies, and it would be useful in many situations to define dynamically similar surrogates. In the second part of this talk I will present an accepted macroscale system of partial differential equations including fully coupled incompressible Navier-Stokes fluid dynamics, quite general nonlinear elasticity, and rigid body mechanics for a complex mechanical system, and show by rigorous reasoning that there is a set of scaling laws where length, time, density, elastic modulus, viscosity, and gravitational constant undergo nontrivial scaling. I have applied these laws to a diverse range of systems in nature, including birds, fish, mammals, reptiles, amphibians, crustaceans, microorganisms, and plants. The uniform agreement of the scaling laws with the dynamics of fauna, flora, and microorganisms supports the dominating role of coupled nonlinear elasticity and fluid dynamics in evolutionary development. I will also present the predictions for some prehistoric cases for which observations are unavailable, as well as applications to space exploration. Overall, my talk illustrates that nonlinear mechanics is a powerful predictive tool to address the complexity of modern engineering problems.

Bio: Huan Liu is a Drinkward Postdoctoral Fellow at California Institute of Technology. She received her Ph.D. in Aerospace Engineering and Mechanics from University of Minnesota in 2024. Prior to her Ph.D., Huan obtained her M.S. in Mechanics and Engineering Science from Peking University in 2019, and her B.S. in Engineering Mechanics from Dalian University of Technology in 2016. She is also a co-founder of WhirrlEnergy LLC, a startup focused on revolutionizing the wind energy industry by producing clean energy through a highly optimized vertical-axis wind turbine. Her interests are focused on understanding the complex nonlinear mechanics in materials, structures, and coupled mechanical systems, discovering new materials and structures, and fostering sustainability.

NOTE: At this time, in-person Mechanical and Civil Engineering Lectures are open to all Caltech students/staff/faculty/visitors.