@article {67, title = {Transient shape morphing of active gel plates: Geometry and physics}, journal = {Soft Matter}, volume = {18}, year = {2022}, pages = {5867-5876}, chapter = {5867}, abstract = {

The control of shape in active structures is a key problem for the realization of smart sensors and actuators, which often draw inspiration from natural systems. In this context, slender structures, such as thin plates, have been studied as a relevant example of shape morphing systems where curvature is generated by in-plane incompatibilities. In particular, in hydrogel plates these incompatibilities can be programmed at fabrication time, such that a target configuration is attained at equilibrium upon swelling or shrinking. While these aspects have been examined in detail, understanding the transient morphing of such active structures deserves further investigation. In this study, we develop a geometrical model for the transient shaping of thin hydrogel plates by extending the theory of non-Euclidean plates. We validate the proposed model using experiments on gel samples that are programmed to reach axisymmetric equilibrium shapes. Interestingly, our experiments show the emergence of non-axisymmetric shapes for early times, as a consequence of boundary layer effects induced by solvent transport. We rationalize these observations using numerical simulations based on a detailed poroelastic model. Overall, this work highlights the limitations of purely geometrical models and the importance of transient, reduced theories for morphing plates that account for the coupled physics driving the evolution of shape. Computational approaches employing these theories will allow to achieve accurate control on the morphing dynamics and ultimately advance 4D printing technologies.\ 

}, keywords = {active materials, hydrogel plates, Transient morphing}, doi = {10.1039/D2SM00669C}, author = {Valentina Damioli and Erik Zorzin and Antonio DeSimone and Giovanni Noselli and Alessandro Lucantonio} } @article {61, title = {A theoretical study on the transient morphing of linear poroelastic plates}, journal = {Journal of Applied Mechanics}, volume = {88}, year = {2021}, pages = {031008}, abstract = {

Based on their shape-shifting capabilities, soft active materials have enabled new possibilities for the engineering of sensing and actuation devices. While the relation between active strains and emergent equilibrium shapes has been fully characterized, the transient morphing of thin structures is a rather unexplored topic. Here, we focus on polymer gel plates and derive a reduced linear model to study their time-dependent response to changes in the fluid environment. We show that independent control of stretching and bending deformations in stress-free conditions allows to realize spherical shapes with prescribed geometry of the mid-plane. Furthermore, we demonstrate that tensile (compressive) membrane stresses delay (accelerate) swelling-induced shape transitions compared to the stress-free evolution. We believe that these effects should be considered for the accurate design of smart systems and may contribute to explain the complexity of natural shapes.\ 

}, keywords = {Dimensional reduction, Polymer gel plates, Sensing and actuation devices, Shape-shifting structures, Transient morphing}, doi = {10.1115/1.4048806}, author = {Andrini, Dario and Lucantonio, Alessandro and Noselli, Giovanni} } @article {60, title = {A theoretical study on the transient morphing of linear poroelastic plates}, journal = {Journal of Applied Mechanics}, volume = {In press}, year = {2020}, abstract = {

Based on their shape-shifting capabilities, soft active materials have enabled new possibilities for the engineering of sensing and actuation devices. While the relation between active strains and emergent equilibrium shapes has been fully characterized, the transient morphing of thin structures is a rather unexplored topic. Here, we focus on polymer gel plates and derive a reduced linear model to study their time-dependent response to changes in the fluid environment. We show that independent control of stretching and bending deformations in stress-free conditions allows to realize spherical shapes with prescribed geometry of the mid-plane. Further, we demonstrate that tensile (compressive) membrane stresses delay (accelerate) swelling-induced shape transitions, as compared to the stress-free evolution. We believe that these effects should be considered for the accurate design of smart systems and may contribute to explain the complexity of natural shapes.\ 

}, keywords = {Dimensional reduction, Polymer gel plates, Sensing and actuation devices, Shape-shifting structures, Transient morphing}, doi = {10.1115/1.4048806}, author = {Dario Andrini and Alessandro Lucantonio and Giovanni Noselli} }