Parallel Helix Actuators for Soft Robotic Applications.

Area of Science:

• Robotics and Soft Matter Engineering
• Materials Science and Manufacturing

Background:

• Fabricating soft pneumatic bending actuators is complex, requiring multiple steps for internal geometry and material bonding, especially for small-scale, multi-chamber designs.
• Existing designs often lead to poor repeatability, excessive ballooning, and reduced bending efficiency due to simple internal geometries or material constraints.

Purpose of the Study:

• To present a simplified, single-material molding technique for fabricating complex soft pneumatic bending actuators.
• To demonstrate the effectiveness of helical internal structures in controlling actuator performance and enabling compact designs.

Main Methods:

• A novel single-material molding technique utilizing parallel cores with helical features was developed.
• Three-chambered actuator designs with varied helical features were fabricated and evaluated for bending angles, workspace coverage, and load-carrying capacity.
• Forward kinematic models were developed and calibrated based on the constant curvature assumption.

Main Results:

• The helical design successfully restricted radial expansion, enabling compact, multi-chambered actuators with complex internal geometry in a single molding step.
• Actuators achieved significant bending angles (>180°), demonstrated 3D workspace coverage, and supported up to three times their bodyweight.
• Calibrated kinematic models achieved a mean tip error of 4.1 mm, accurately predicting actuator behavior.

Conclusions:

• The presented fabrication technique offers a simple, inexpensive, and repeatable method for producing high-performance soft pneumatic bending actuators.
• The helical core design is crucial for achieving controlled expansion and efficient bending in small-diameter actuators.
• This technique has broad potential for scalable, application-specific designs in soft robotics, surgical tools, and locomotion systems.