Magnetorheological Fluid-Filled Origami Joints With Variable Stiffness Characteristics

Origami technology has applications in diverse areas, such as metamaterials, space structures, and haptic interfaces due to the low-cost manufacturing, rapid assembly, and compact structures. Existing origami robots, however, often lack variable stiffness due to the intrinsic properties of conventional origami structures made of rigid facets and flexible joints. In this article, we present a design of magnetorheological (MR) fluid-filled origami joints with variable stiffness characteristics. Compared with existing approaches to realize controllable origami joints stiffness, our proposed method has the advantage of magnetically remote control. To predict the joint stiffness under different magnetic flux densities, we derive a theoretical model and calibrate it by test. Subsequently, to demonstrate MR fluid-filled origami joints can apply in more complex origami structures, we design a modified thick Yoshimura structure and a Kresling structure that can achieve stiffness enhancement of 59.2 and 83.6%, respectively. Also, we introduce jamming behavior into the joint to achieve the same capability of variable stiffness while utilizing a relatively weak magnetic setup. Additionally, we fill MR fluid into the origami facets to develop an origami robot that can carry loads while crawling on flat ground and climbing on an inclined surface.