Transient shape morphing of active gel plates: geometry and physics.

Area of Science:

• Materials Science
• Mechanical Engineering
• Soft Matter Physics

Background:

• Active structures, inspired by nature, are key for smart sensors and actuators.
• Thin hydrogel plates exhibit shape morphing driven by programmed in-plane incompatibilities during swelling or shrinking.
• While equilibrium shapes are understood, the transient morphing dynamics of these active structures require further investigation.

Purpose of the Study:

• To develop a geometrical model for transient shaping of thin hydrogel plates.
• To investigate the influence of coupled physics on shape evolution during morphing.
• To advance the control and understanding of shape dynamics in active materials.

Main Methods:

• Extension of the theory of non-Euclidean plates to model transient morphing.
• Experimental validation using programmed hydrogel samples.
• Numerical simulations employing a detailed poroelastic model to rationalize observations.

Main Results:

• The developed geometrical model captures transient shape changes in hydrogel plates.
• Experiments revealed emergent non-axisymmetric shapes at early times, deviating from purely geometrical predictions.
• Poroelastic simulations confirmed boundary layer effects from solvent transport as the cause of transient non-axisymmetry.

Conclusions:

• Purely geometrical models have limitations in predicting the full morphing dynamics of hydrogel plates.
• Transient, reduced theories incorporating coupled physics are essential for accurate shape control.
• Computational models based on these theories will enhance 4D printing and the design of smart devices.