Are active soft particles suitable for particle jamming actuators?

Soft grippers show adaptability and flexibility in grasping irregularly shaped and fragile objects. However, the soft grippers' low loading capacity and limited shaped fitting ability are the main limitations for developing large-scale applications, especially for heavy objects and objects with sharp edges. The particle jamming effect has emerged as an essential actuation method to adjust the stiffness of soft grippers and enhance the lifting force applied to heavy objects. However, in many large and more serious practical grasping applications, soft actuators are expected to show large scales and several-fold stiffness change, which is challenging to achieve the jamming effect in pneumatic or hydraulic systems. In this paper, a novel active particle jamming method is proposed for the design of a particle jamming-based soft gripper. The proposed method uses active hydrogel particles instead of vacuum pressure to achieve the jamming effect. Additionally, the bending behaviors are implemented based on the jamming effect and actuator design. The numerical model is carried out to explore the actuator behaviors, and a brief experiment case is conducted to verify the feasibility. The results indicated that the proposed actuator achieves the functionality of bending actions by swelling the hydrogel particles. The bending performance is enhanced by lowering the trigging temperature and increasing the thickness of the strain-limit layer. Additionally, there is a transition state from bending to curling when increasing the layer of particles.