4D printing with robust thermoplastic polyurethane hydrogel-elastomer trilayers

Transformer Hydrogels: A Review

“…The hydrogels are typically layered by spin coating, drop‐casting or nozzle printing, which afford control over the thickness of the layers. Researchers combine two or more hydrogel layers with different mechanical and swelling properties in a spatially predefined sequence and orientation . An example is the pairing of an active soft hydrogel layer capable of swelling with a relatively stiff passive layer with relatively nonswelling characteristics .…”

Smart polymers and nanocomposites for 3D and 4D printing

“…Baker et al [117] 3D printed trilayer origami-inspired structures including a polyurethane hydrogel core and polyurethane elastomer skins. Discrete localized gaps at the elastomeric skin were made to act as active hinges.…”

“…The red parts are the swellable hydrogel and the white parts are the rigid polymer [116]. b) Origami-inspired trilayer structure folding upon hydration (core from polyurethane hydrogel and skins from polyurethane elastomer) [117]. C) DIW printing of composite hydrogel with the shear-induced alignment of cellulose fibrils to create anisotropic swelling (left) 3D…”

An insight into biomimetic 4D printing

“…[61][62][63][64] The most important thing that must be taken into consideration is modeling for the sensitivity towards stimuli, such as light and heat, in terms of triggering their shape-changing features as it happens in the case of owers. [65][66][67][68][69][70][71][72][73] The continuum mechanics in such cases were started with the rough design space solution, progressed through the discretization of the model, and then ended with the computation of the voxelized object deformation. 60 The mass-spring modeling was considered fundamental to the concept used behind the denition of the design space and discretization.…”