Sequential metamaterials with alternating Poisson's ratios

Area of Science:

• Materials Science
• Mechanical Engineering
• Physics

Background:

• Mechanical metamaterials typically achieve fixed Poisson's ratios through microarchitecture deformation.
• Existing designs lack the ability to temporally and spatially alternate Poisson's ratios during deformation.
• This limitation hinders the development of advanced smart materials for complex mechanical information processing.

Purpose of the Study:

• To introduce novel periodic and graded mechanical metamaterials capable of passively alternating Poisson's ratios.
• To enable dynamic shape-morphing applications by processing mechanical information through time-ordered signals.
• To provide a design methodology and software tool for creating materials with user-specified alternating Poisson's ratios.

Main Methods:

• Leveraging principles of differential stiffness and self-contact within the metamaterial microarchitecture.
• Developing an analytical approach and a complementary software tool for designing materials in 2D and 3D.
• Utilizing sequential deformation computations significantly faster than traditional finite-element methods.

Main Results:

• Demonstrated passive, user-specified alternating Poisson's ratios in both periodic and graded metamaterials.
• Validated the predicted alternating Poisson's ratios through experiments on macro- and micro-scale designs.
• The developed software tool offers an order of magnitude speedup in sequential deformation computation.

Conclusions:

• The introduced mechanical metamaterials offer a new paradigm for passive, programmable shape-morphing.
• This work paves the way for smart materials that can dynamically respond to mechanical stimuli without active control.
• The design tool accelerates the development of advanced metamaterials with complex, time-varying mechanical properties.