Internally architectured materials with directionally asymmetric friction

Area of Science:

• Materials Science
• Tribology
• Mechanical Engineering

Background:

• Friction is a fundamental property of materials, typically considered isotropic.
• Directional control of friction forces remains a significant challenge in material design.

Purpose of the Study:

• To propose and characterize Internally Architectured Materials (IAMs) exhibiting directionally asymmetric friction.
• To develop a theoretical framework for understanding friction anisotropy.
• To demonstrate the potential of IAMs in applications like mechanical rectification.

Main Methods:

• Designing and fabricating layered materials or ribbed structures with inclined elements.
• Developing a theory to describe directionally asymmetric friction and friction anisotropy (ξ-coefficient).
• Testing prototype IAMs, including those manufactured via 3D printing, to measure friction asymmetry.

Main Results:

• IAMs were designed to translate normal deformation into tangential forces, mimicking inclined bristles.
• Friction anisotropy (ξ) of the order of 10 was achieved, with values exceeding 20 for 3D-printed prototypes.
• Directionally dependent bending stiffness of ribs further enhanced friction asymmetry.

Conclusions:

• IAMs demonstrate a novel mechanism for achieving significant friction asymmetry.
• The developed theory accurately describes the observed friction behavior.
• IAMs offer potential for applications in unidirectional locomotion and energy harvesting from vibrations.