Dimpled frames: morphing attributes, multistability and feeble memory

Abstract

The rise of mechanically intelligent systems -- that sense, compute and adapt with minimal electronics -- is increasing the need for devices that can store mechanical memory. Here, we introduce dimpled frames as structural analogs to soft multistable dimpled sheets, whose unique memory attributes manifest as a dependency of their final shape on the sequence of actuation of each bistable dimple. Our structures feature sinusoidal arches connected at multiple locations of a base with polygonal cutouts. Each arch can snap through a cutout, yielding local bistability and, potentially, global multistability. Through extensive experiments and efficient numerical simulations based on discrete elastic rods, we unveil the link between the geometrical parameters of our structures and their capacity to display mechanical memory. Specifically, we show that memory is 'feeble' in our structures, and will vanish if the parameters are not chosen properly -- shedding further light on the requirements for arrays of bistable units to display mechanical memory. Our dimpled frames -- that can be made of stiff materials with low damping -- could provide memory storage options for vibration-based mechanical computing systems.