Site-Specific Pre-Swelling-Directed Morphing Structures of Patterned Hydrogels

An Anisotropic Hydrogel by Programmable Ionic Crosslinking for Sequential Two-Stage Actuation under Single Stimulus

As one of the most important anisotropic intelligent materials, bi-layer stimuli-responsive actuating hydrogels have proven their wide potential in soft robots, artificial muscles, biosensors, and drug delivery. However, they can commonly provide a simple one-actuating process under one external stimulus, which severely limits their further application. Herein, we have developed a new anisotropic hydrogel actuator by local ionic crosslinking on the poly(acrylic acid) (PAA) hydrogel layer of the bi-layer hydrogel for sequential two-stage bending under a single stimulus. Under pH = 13, ionic-crosslinked PAA networks undergo shrinking (-COO−/Fe3+ complexation) and swelling (water absorption) processes. As a combination of Fe3+ crosslinked PAA hydrogel (PAA@Fe3+) with non-swelling poly(3-(1-(4-vinylbenzyl)-1H-imidazol-3-ium-3-yl)propane-1-sulfonate) (PZ) hydrogel, the as-prepared PZ-PAA@Fe3+ bi-layer hydrogel exhibits distinct fast and large-amplitude bidirectional bending behavior. Such sequential two-stage actuation, including bending orientation, angle, and velocity, can be controlled by pH, temperature, hydrogel thickness, and Fe3+ concentration. Furthermore, hand-patterning Fe3+ to crosslink with PAA enables us to achieve various complex 2D and 3D shape transformations. Our work provides a new bi-layer hydrogel system that performs sequential two-stage bending without switching external stimuli, which will inspire the design of programmable and versatile hydrogel-based actuators.

A Complex Zeolite Containing Multiple Ring Sizes in a Single Channel: One-Dimensional Zeolite UZM-55

Zeolites are porous aluminosilicate materials utilized in a variety of sorption, separation, and catalytic applications. The oil refining industry in particular has seen a number of significant advances due to the introduction of new technologies enabled by new zeolites. Of particular importance are zeolites with 10- or 12-membered ring pores, resulting in pore shapes and sizes appropriate for the interaction with small hydrocarbon molecules. Here, the synthesis of a new zeolite UZM-55 is reported and the idealized structure thereof is presented. The most complex structure solved to date, UZM-55 possesses a large triclinic unit cell containing 52 T-sites. The material uniquely contains both 10- and 12-membered ring pores in a single, undulating one-dimensional channel, the first example in a zeolitic material of multiple delimiting rings in a single channel. This discovery opens new opportunities in shape-selective adsorption and catalysis. Demonstrated here is the unique adsorption behavior of UZM-55, shown both experimentally and computationally to adsorb one nonane molecule per unit cell in a linear conformation.

Actuating and memorizing bilayer hydrogels for a self-deformed shape memory function

A general strategy for fabricating a double layer self-deformed shape memory hydrogel which includes a thermo-responsive actuating layer and a pH-responsive memorizing layer is presented.