Programmable Auxeticity in Hydrogel Metamaterials via Shape-Morphing Unit Cells

Area of Science:

• Materials Science
• Mechanical Engineering
• Polymer Science

Background:

• Mechanical metamaterials exhibit unique properties derived from their structure.
• Conventional metamaterials lack reconfigurability after manufacturing.

Purpose of the Study:

• To introduce shape-morphing capabilities into hydrogel metamaterials.
• To achieve programmable auxeticity through controlled reconfiguration.

Main Methods:

• Spatio-selective integration of responsive actuating elements into a hydrogel metamaterial.
• Utilizing thermal control to adjust the unit cell geometry.
• Finite element (FE) simulation for prediction and verification.

Main Results:

• Successfully reconfigured the mesoscale unit cell geometry of a honeycomb structure.
• Achieved programmable auxeticity with Poisson's ratios ranging from negative to positive.
• Demonstrated precise control over the unit cell angle (68° to 107°) via thermal stimulus.

Conclusions:

• Shape-morphing hydrogel metamaterials offer a novel strategy for reconfigurable materials.
• The developed concept extends hydrogel applications in areas like mechanical computing and soft robotics.
• This approach enables the creation of metamaterials with tunable mechanical responses.