Active Metamaterials with Tunable Shear Nonreciprocity and Nonlinear Dynamics.

Area of Science:

• Mechanical Engineering
• Materials Science
• Physics

Background:

• Actively tunable mechanical metamaterials are crucial for adaptive structures in smart machines.
• Existing designs often lack control over transverse deformation, reciprocity, and linear dynamics.

Purpose of the Study:

• To propose a novel gear-based design paradigm for mechanical metamaterials.
• To enable simultaneous control of translational/torsional stiffnesses, shear nonreciprocity, and nonlinear dynamics.

Main Methods:

• Utilized Taiji planar gears and planetary gear assemblies as fundamental building blocks.
• Developed analytical models to elucidate underlying mechanisms and design freedoms.

Main Results:

• Achieved 30-100x continuous tuning of shear stiffness and over 100x tuning of nonreciprocity ratio.
• Demonstrated programmable nonlinear dynamics controlled by static nonreciprocity.
• Constructed meta-resonators with broadly tunable resonant frequencies.

Conclusions:

• The proposed gear-based metamaterials overcome limitations of existing designs.
• This work provides a practical pathway for controlling linear and nonlinear deformations, waves, and vibrations.
• Offers significant advancements for adaptive structures and smart machines.