Magnetically controlled bio-inspired elastomeric actuators with high mechanical energy storage

A Variable Stiffness Bioinspired Swallowing Gripper Based on Particle Jamming

As the chameleon tongue swallows the food, it wraps the entrapped meat around the food, ensuring that it is completely enclosed and preventing it from falling off. Inspired by swallow behavior, this article introduces the design, manufacture, modeling, and experimentation of a variable stiffness swallowing gripper (VSSG). The VSSG is comprised of an intimal membrane, an adventitial membrane, and an internal medium of particles and liquid water. This gripper integrates swallowing behavior with a particle jamming mechanism, exhibiting both soft and rigid state. In the soft state, it gently swallows objects by folding its intimal and adventitial membranes. In the rigid state, the bearing capacity is enhanced by promoting particle jamming phenomenon through pumping out liquid water. Therefore, the proposed gripper has the capability to mitigate the issue of extrusion force applied on the object, while simultaneously enhancing the load-bearing capacity of swallowing gripper. In this article, the swallowing principle of the VSSG is analyzed, the mathematical model of the holding force and extrusion force is deduced, and preliminary experiments are carried out to verify the actual gripping effect of the gripper. The experimental results demonstrate that the VSSG can successfully swallow objects of different shapes in the soft state, exhibiting excellent flexibility and adaptability. The carrying capacity of the gripper in the rigid state increased approximately twofold compared with its soft state. In addition, several swallowing grippers with different filling medium were comparatively studied, and the results show that the VSSG has a large load-bearing capability.

4D Printing of Ultrastretchable Magnetoactive Soft Material Architectures for Soft Actuators

Magnetoactive soft materials (MSMs) comprising magnetic particles and soft matrices have emerged as smart materials for realizing soft actuators. 4D printing, which involves fabricating 3D architectures that can transform shapes under external magnetic fields, is an effective way to fabricate MSMs-based soft actuators with complex shapes. The printed MSMs must be flexible, stretchable, and adaptable in their magnetization profiles to maximize the degrees of freedom for shape morphing. This study utilizes a facile 4D printing strategy for producing ultrastretchable (stretchability > 1000%) MSM 3D architectures for soft-actuator applications. The strategy involves two sequential steps: (i) direct ink writing (DIW) of the MSM 3D architectures with ink composed of NdFeB and styrene-isoprene block copolymers (SIS) at room temperature and (ii) programming and reconfiguration of the magnetization profiles of the printed architecture using an origami-inspired magnetization method (magnetization field, Hm = 2.7 T). Various differently shaped MSM 3D architectures, which can be transformed into desired shapes under an actuation magnetic field (Ba = 85 mT), are successfully fabricated. In addition, two different soft-actuator applications are demonstrated: a multifinger magnetic soft gripper and a Kirigami-shaped 3D electrical switch with conductive and magnetic functionalities. Our strategy shows potential for realizing multifunctional, shape-morphing, and reprogrammable magnetoactive devices for advanced soft-actuator applications.