Amplitude tuning is an important strategy in animals employing traveling wave patterns, enhancing their adaptability to unstructured environments. This paper proposes, for the first time, an amplitude tuning method that leverages the compliance of a soft corkscrew by twisting its ends. An amplitude tunable traveling wave robot (ATWBot) is developed, consisting of a soft corkscrew housed in a high DOF cage and driven by only two servos. The soft corkscrew and cage are monolithically 3D-printed. ATWBot achieves a wide range of active amplitude tuning with passive compliance adaptation, and can extend its morphology to a coiled configuration, enabling clamping and rolling. A comprehensive model is built for the twisted soft corkscrew geometry, proving that the robot's speed is decoupled from amplitude variations during twisting. A genetic algorithm is used to optimize the soft corkscrew for achieving the fastest speed while matching the cage geometry. Experiments demonstrate that the combination of active amplitude tuning and passive body compliance enables the robot to adapt to unstructured terrains including slits, steps, gaps, converging tunnels, slopes, and swimming.

Slow-speed animals can also exhibit remarkable capabilities, as seen in snails that crawl while maintaining adhesion. Snails have inspired researchers to develop traveling wave-based robots and suction robots; however, the combination of traveling wave propulsion with suction ability remains a challenge. In this paper, we propose a snail-inspired robot that integrates a corkscrew propulsion mechanism with distributed suction cups, enabling it to crawl upside down on the ceiling. The propulsion model of the corkscrew generating the traveling wave is derived, and a temporal-spatial decomposition method is applied to validate the high efficiency of traveling wave generation. The trade-off between wave amplitude and suction cup depth is investigated to determine an optimized configuration. The results show that the robot’s speed aligns well with the propulsion model. The traveling wave ratio calculated from experiments is 0.938. The optimized configuration consists of a corkscrew with a 14 mm diameter and suction cups with a 2.5 mm depth, achieving a crawling speed of 3.02 ± 0.28 mm/s while moving upside down. The combination of the proposed smooth traveling wave generation method and distributed suction cups enables the robot to crawl upside down while carrying a 200 g load and to climb a vertical wall, like a natural snail.

Origami provides a unique tool for the design of robotic frames owing to its simple shaping principle by “folding.” However, achieving the fast and reversible activeness of a highly reconfigurable structure remains challenging owing to the limitations of accessible actuators. In particular, it is difficult to find an actuator that can realize a simultaneously large, rapid, reversible, and stable movement while leading to a favorable form factor for the origami. To overcome this, in this article, we propose a 3-D shape-shifting system consisting of a morphing origami block that complements the stability problem of shape memory alloy wire actuators by tuning its structural characteristics. This cooperative scheme improves the reversibility and stability of the shape-shifting system, which enables the rapid transformation with high degrees of freedom unlike in existing programmable origami. As a stand-alone unit of transformation, morphing block equipped with deployable mechanism and actuators weighs 6 g and has a volume change factor of ten. Furthermore, the transformation time in both directions is less than 5 s, and the block can carry more than 120 g of payload in the deployed state. The proposed system composed of multiple origami blocks can reconfigure itself into diverse 3-D target shapes.

In this paper, we propose a new shape-shifting system. Shape-shifting is achieved by the integration of arranged identical transformable units. These are self-folding origami modules that transform their shape from a cubic to a flat shape, and vice versa, similarly to a three-dimensional (3D) morphing pixel. By changing the shape of individual modules, the system can generate desired shapes. Each module is based on a modified Kresling pattern, which has bi-stability during deployment so that it can maintain its shape in both states without any actuator force. Also, it can rapidly and reversibly transform its shape via folding and unfolding motions that are generated by a low-profile torsional SMA wire actuator positioned at fold lines. This approach is a hybrid of the modular and folding approaches so that the system can generate shape-shifting without complicated communication methodology between modules and bulky infrastructure, and has fast, compact and lightweight hardware. We demonstrate performance with a 3×3 matrix form of this module (40 mm side length) that can make five different shapes and it required only 15 seconds per transformation. This new shape-shifting system could be applied to design multi-functional self-folding origami such as a morphing 3D map.

One of the major problems in utilizing origami structures is ensuring variable stiffness; a deployable structure needs to become stiff or flexible according to the requirements of its use in an application. In this study, we present a self-deploying tubular origami mechanism that switches between two distinctive states: small and flexible at its normal state and rigid and stiffened at a locked state. By embedding compact torsional SMA actuators into the mechanism in a novel way through stitching, the process of deploying from the normal to the locked state proceeds in a simple and low-profile manner. With global heating, the torsional SMA wires activate a buckling effect that draws a radical change of folding line from one diagonal to another in every unit tile of the tube, creating axial stiffness. The activated structure, which weighs only 2.9 g, can endure a load of 2.7 kg or more. Additionally, since it does not require bulky actuators, this origami structure can be highly mobile and small in size. This novel origami mechanism is expected to be useful in a wide variety of applications, such as aerospace equipment, mobile architecture, and medical devices, especially those used in minimally invasive surgery (MIS).

The unique characteristics of origami to realize 3-D shape from 2-D patterns have been fascinating many researchers and engineers. This paper presents a fabrication of origami patterned fabric wheels that can deform and change the radius of the wheels. PVC segments are enclosed in the fabrics to build a tough and foldable structure. A special cable driven mechanism was designed to allow the wheels to deform while rotating. A mobile robot with two origami wheels has been built and tested to show that it can deform its wheels to overcome various obstacles.