Directed Instability as a Mechanism for Fabricating Multistable Twisting Microstructure

Herein, The study of multistable structures, particularly those that can twist, has attracted significant attention in recent years. This ability to transition between multiple stable geometries of these structures paves the way for advances in diverse applications, such as morphing structures and robot actuation mechanisms. Conventional methods of designing and fabricating these structures often involve complex and resource-intensive fabrication processes, which restrict their widespread adoption and limit their miniaturization. Here, we present a novel inflatable multistable twisting structure, based on helical folds of an elastic tube. Our fabrication approach utilizes directed mechanical instability as a method for a rapid fabrication, which is readily implemented at various length scales. We developed a theoretical model for the deformation of the bistable helical elements comprising the twisting structure, and compared the theoretical results to the experimental data. Furthermore, we demonstrate our fabrication methodology using a variety of polymers, including medical grade polymers, as well as various inner radii ranging from 5 mm to 44 μm and thicknesses of the tubes’ walls ranging from 250 μm to 19 μm.