Self‐Oscillating 3D Printed Hydrogel Shapes

Abstract

The BZ reaction involves the continuous exchange of electrons, producing a dynamic shift from a reduced to oxidized state of a metallic atom. This active electron movement results in spatiotemporal patterns that provide a platform to study and understand nature. [3] A range of self-oscillating polymers are designed by incorporating metal catalysts to polymer matrices. [4] Different architectures are developed based on BZ reaction in past including porous microstructures, [5] microgels, [6,7] comb-type gels, [8] polyrotaxanes, [9] polymer brushes, [10] and micelles. [11] Furthermore, the force generated by the BZ reaction in the self-oscillating polymers have be used as propulsive system: [12] tubular-shaped gels; [13] ciliary motion in arrays of PMMA gels; [14] active surfaces transported microbodies; [15] and a cylinder-shaped gel self-walking structure. [16] Previous studies have confined the BZ reaction in different hydrogel systems fabricated using different approaches. Initial studies used flask-mediated polymerizations and microfluidics to produce a variety of hydrogels, [16,17] consisting of micelles Materials, [18] linear chains, [7,19] brushes, [20] etc. Microfluidics can fabricate 3D hydrogels with precise control, but their size is limited to the macro-and micro-length scale. [21] Other studies employed engineering techniques such as UV patterning [22] and microdispensing [23] to fabricate hydrogels; however, the Belousov-Zhabotinsky (BZ) reactions have been used to investigate periodic spatial patterns due to the oscillatory nature of the reaction. However, these systems have not been confined, nor controlled, in macro-scaled architectures, making it hard to translate observations to natural behavior. Here, a poly(electrolyte) complex is designed that can be ionically or covalently reinforced to construct 3D geometries with additive manufacturing techniques. Printed geometries varied in shape, size, and angle to investigate spatiotemporal pattern formation in 3D. Size variations correlated to trends in oscillating pattern frequencies, demonstrating a geometry effect on spatial alterations. Overall, the combination of 3D printing techniques with selfoscillating chemical reactions allows to model, study, and further understand macro-scale patterns observed in nature. The proposed approach can be used to design smart structure to replicate biological oscillators such as cardiac arrhythmias, neuron signaling, and camouflage skin patterns.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/admt.202100418.

Injectable, Self‐healing, and 3D Printable Dynamic Hydrogels

“…[9,11,18,19] Dynamic hydrogels with shear-thinning and shear-recovery ability can be used for 3D printing as hydrogel bioinks. [20,21] To be printed, hydrogel bioinks must be easily deposited on a surface and then maintained a printed structure. Shear-thinning and shear-recovery hydrogels enable the formation of thin filaments for high-resolution printing due to rapid deformation and recovery during the printing process.…”

Dynamically crosslinked thermoresponsive granular hydrogels

“…The hydrogel inks for 3D extrusion‐based printing should equip good injectability, shear‐thinning, and self‐healing ability. Earlier we designed a range of hydrogel inks with shear‐thinning and self‐healing characteristics 36–39 . Based on similar approaches, we evaluated the use of granular hydrogels containing microgel assemblies for potential 3D printing.…”

“…Earlier we designed a range of hydrogel inks with shear-thinning and self-healing characteristics. [36][37][38][39] Based on similar approaches, we evaluated the use of granular hydrogels containing microgel assemblies for potential 3D printing. The microgel assemblies were able to form hydrogel filaments with 0.4 and 1 mm extrusion tips (Figure 5A).…”

Periodical propagation of torsion in polymer gels

“…Chemical waves are generated within the BZ gel once the BZ gel length is sufficiently longer than the wavelength of the chemical wave. We have observed the peristaltic motion of the locally swollen area propagating as the chemical wave propagates [19][20][21][22].…”