Non-reciprocal and non-Newtonian mechanical metamaterials

Area of Science:

• Solid mechanics
• Metamaterials science
• Non-Newtonian dynamics

Background:

• Non-Newtonian liquids exhibit velocity-dependent responses, unlike conventional materials.
• Reciprocity in passive elastic media hinders directional responses in phononics.
• Theoretical work suggests resonant quasi-rigid bodies can enable non-reciprocal metamaterials.

Purpose of the Study:

• To design a solid mechanical metamaterial with unidirectional shock resistance.
• To create a material that goes beyond Newton's second law, analogous to non-Newtonian fluids.
• To experimentally validate non-Newtonian and non-reciprocal elastic behavior.

Main Methods:

• Finite element analysis for metamaterial design.
• 3D printing (Fused Deposition Modeling and two-photon lithography) for fabrication.
• Dynamical velocity-dependent experiments to measure elastic response.

Main Results:

• Successful design and fabrication of a mechanical metamaterial.
• Demonstration of unidirectional shock resistance.
• Experimental validation of velocity-dependent, non-Newtonian elastic response.
• Observation of intrinsic non-reciprocal behavior upon impact reversal.

Conclusions:

• The designed mechanical metamaterial exhibits non-Newtonian elastic properties.
• The structure achieves unidirectional shock resistance, a non-reciprocal phenomenon.
• This work provides a pathway for developing passive non-reciprocal mechanical materials.