A Human-Inspired Soft Finger with Dual-Mode Morphing Enabled by Variable Stiffness Mechanism.

Area of Science:

• Robotics
• Materials Science
• Biomimetics

Background:

• Achieving variable stiffness in soft robotic fingers is crucial for versatile manipulation tasks.
• Existing soft actuators often struggle to balance compliance with the need for increased rigidity.

Purpose of the Study:

• To propose and demonstrate a multijoint soft finger with dual morphing capabilities through active/passive variable rigidity.
• To enable independent adjustment of phalangeal stiffness for different manipulation requirements.

Main Methods:

• Fabrication of a soft finger using conductive thermoplastic starch polymers (CTPSs) embedded in U-shape-joint pneumatic actuators.
• Integration of Yoshimura origami structures to mimic biological ligaments for passive deformation matching.
• Electrothermal activation of CTPSs for independent stiffness control of phalanges.

Main Results:

• The soft finger exhibits dual morphing modes: stiffened phalanges (Mode 1) for heavy loads and softened phalanges (Mode 2) for large deformation contact.
• Mode 1 significantly enhances output force (over 2x) and stiffness (over 5x) compared to a pure soft finger.
• Mode 2 maintains similar compliance while allowing for large deformations.
• A three-fingered gripper successfully manipulated diverse objects and lifted a 1460g dumbbell with a 7.6 load/weight ratio.

Conclusions:

• The proposed dual-mode morphing soft finger effectively addresses the challenge of variable stiffness control in soft robotics.
• This technology offers a promising solution for dexterous manipulation, heavy load handling, and delicate object interaction in robotic applications.