Multiple configuration transitions of soft actuators under single external stimulus.

Area of Science:

• Materials Science
• Robotics
• Mechanical Engineering

Background:

• Soft actuators are vital for applications like soft robotics and medical instruments.
• Current soft actuators typically exhibit only one configuration transition per stimulus.
• Achieving multiple, controllable shape transitions is a key challenge in soft actuator development.

Purpose of the Study:

• To develop a novel soft actuator capable of multiple configuration transitions under a single stimulus.
• To investigate the factors governing these multiple transitions.
• To demonstrate advanced functionalities enabled by this multi-transition capability.

Main Methods:

• 3D printing of parallel strips with crescent cross-sections onto a PDMS film.
• Swelling the actuator in ethyl acetate to induce shape changes.
• Experimental investigation, theoretical analysis, and finite element simulations to understand mechanisms.
• Demonstration of grasp-release-re-grab functionality.

Main Results:

• The novel soft actuator exhibits multiple, distinct configuration transitions upon swelling in ethyl acetate.
• Geometric asymmetry, fabrication heterogeneity, differential swelling, and geometric parameters synergistically control the morphing behavior.
• The underlying mechanisms were elucidated through integrated experimental, theoretical, and simulation approaches.
• A grasp-release-re-grab function was successfully demonstrated using a single stimulus.

Conclusions:

• The developed soft actuator offers unprecedented multi-transition capabilities under a single stimulus.
• This work provides fundamental insights into the morphing mechanisms of complex soft actuators.
• The findings pave the way for designing advanced soft actuators with sophisticated functionalities for diverse applications.