3D Printing of Anisotropic Hydrogels with Bioinspired Motion

Abstract

Motion in biological organisms often relies on the functional arrangement of anisotropic tissues that linearly expand and contract in response to external signals. However, a general approach that can implement such anisotropic behavior into synthetic soft materials and thereby produce complex motions seen in biological organisms remains a challenge. Here, a bioinspired approach is presented that uses temperature‐responsive linear hydrogel actuators, analogous to biological linear contractile elements, as building blocks to create three‐dimensional (3D) structures with programmed motions. This approach relies on a generalizable 3D printing method for building 3D structures of hydrogels using a fugitive carrier with shear‐thinning properties. This study demonstrates that the metric incompatibility of an orthogonally growing bilayer structure induces a saddle‐like shape change, which can be further exploited to produce various bioinspired motions from bending to twisting. The orthogonally growing bilayer structure undergoes a transition from a stretching‐dominated motion to a bending‐dominated motion during its shape transformation. The modular nature of this approach, together with the flexibility of additive manufacturing, enables the fabrication of multimodular 3D structures with complex motions through the assembly of multiple functional components, which in turn consist of simple linear contractile elements.

Extrusion 3D Printing of Polymeric Materials with Advanced Properties

“…[ 227 ] The complex bioinspired shape motions could also be realized by combining two printed layers with different orientations (Figure 11D). [ 245 ] A wide range of sophisticated motions from simple bending to coiling and twisting were achieved (Figure 11E). Zhao and co‐workers developed DIW of an elastomer composite containing ferromagnetic microparticles to enable shape changing.…”

“…Reproduced with permission. [ 245 ] Copyright 2019, John Wiley and Sons. E) Various 3D complex shapes could be achieved through controlling the width and angle between the long axis of a bilayer structure in (D) and the direction of the intrinsic curvature (scale bars = 5 mm).…”

Materials as Machines

“…h) DIW of thermally responsive poly( N ‐isopropylacrylamide) hydrogel containing non‐responsive poly(ethylene glycol) (PEG) components facilitating patterned uniaxial contraction. Reproduced with permission 482. Copyright 2015, RSC.…”

“…Spinks and co‐workers demonstrated that the rheological properties needed for controlled printing are accessible through the inclusion of high molecular weight polymer materials 481. Yum recently utilized a similar approach by DIW printing of isotropic PNIPAm hydrogels reinforced with poly(ethylene glycol) (PEG) polymer chains 482. By use of a fugitive carrier (a shear‐thinning material that can be selectively removed from the polymerized hydrogel matrix), a series of homogeneous, multilayer hydrogels are prepared from low molecular precursors.…”

Recent Progress in 3D Printing of Bioinspired Structures

“…The results showed that the bioinspired zigzag designs and bioinspired sinusoidalarchitected designs have a relative higher impact energy, and FIGURE 7 | Heat-induced shape-changing structures fabricated by 3D printing technology. (A) Bioinspired shape-changing structures fabricated by temperature-responsive linear hydrogel (Arslan et al, 2018). Reproduced with the permission of WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.…”