Development of Active-Cells for Macroscopically Deformable Structures

In this paper we describe extensions and improvements upon prior work on “active cells” — small contractile electromechanical elements used in large numbers to create actuated composite structures. Each element (cell) consists of square fiberglass end-pieces encapsulating a bias spring within two telescoping tubes, actuated using two contractile shape memory coils, and occupying approx. 1cm³ when fully contracted. The end-pieces contain conductive interfaces to nearby cells, thus allowing channeling of power through a connected network of cells to provide actuation far from the source of electrical current. Prior work developed the conceptual structure of such a cell as well as preliminary prototypes. This paper describes the attachment of cells to each other and to rapid-prototyped cell interconnects — as well as improved fabrication techniques for the shape-memory coils — resulting in robust actuation for each cell, and the creation of considerably more complex chained and networked composite structures. A detailed exploration of appropriate interconnect mechanisms, powering schemes to provide network-level structural deformations, and examples of multi-cell structures are presented.