Convenient patterning and precisely programmable shape deformations are crucial for the practical applications of shape deformable hydrogels. Here, a facile and versatile computer‐assisted ion inkjet printing technique is described that enables the direct printing of batched, very complicated patterns, especially those with well‐defined, programmable variation in cross‐linking densities, on one or both surfaces of a large‐sized hydrogel sample. A mechanically strong hydrogel containing poly(sodium acrylate) is first prepared, and then digital patterns are printed onto the hydrogel surfaces by using a commercial inkjet printer and an aqueous ferric solution. The complexation between the polyelectrolyte and ferric ions increases the cross‐linking density of the printed regions, and hence the gel sample can undergo shape deformation upon swelling/deswelling. The deformation rates and degrees of the hydrogels can be conveniently adjusted by changing the printing times or the different/gradient grayscale distribution of designed patterns. By printing appropriate patterns on one or both surfaces of the hydrogel sheets, many complex 3D shapes are obtained from shape deformations upon swelling/deswelling, such as cylindrical shell and forsythia flower (patterns on one surface), ding (patterns on both surfaces), blooming flower (different/gradient grayscale distributive patterns on one surface), and non‐Euclidean plates (different/gradient grayscale distributive patterns on both surfaces).

Stimuli-responsive hydrogels with high mechanical strength, programmable deformation, and simple preparation are essential for their practical applications. Here the preparation of tough hydrogels with programmable and complex shape deformations is reported. Janus hydrogels with different compositions and hydrophilic natures on the two surfaces are first prepared, and they exhibit reversible bending/unbending upon swelling/deswelling processes. More impressively, the deformation rate and extent of the hydrogels can further be easily controlled through an extremely simple and versatile ion dip-dyeing (IDD) and/or ion transfer printing (ITP) method. By selectively printing proper patterns on 1D gel strips, 2D gel sheets and 3D gel structures, the transformations from 1D to 2D, 2D to 3D, and 3D to more complicated 3D shapes can be achieved after swelling the ion-patterned hydrogels in water. The swelling-deformable Janus and ion-patterned hydrogels with high mechanical strengths and programmable deformations can find many practical applications, such as soft machines. www.afm-journal.de www.MaterialsViews.com Figure 6. Various 2D and 3D shapes deformed from ion printed 1D, 2D, or 3D hydrogels. a) 1D to 2D shapes; b-d) 2D to 3D shapes; e,f) 3D to complicated 3D shapes. Hydrogel synthesis conditions were: C AAm = 3.0 mol L −1 , C NaAAc = 0.5 mol L −1 , C PVP = 43 mg mL −1 , thickness: 1 mm, or diameter: 14 mm. All scale bars are 5 mm. full paper 8 wileyonlinelibrary.com

High-performance hydrogel electrolytes play a crucial role in flexible supercapacitors (SCs). However, the unsatisfactory mechanical properties of widely used polyvinyl alcohol-based electrolytes greatly limit their use in the flexible SCs. Here, a novel LiSO-containing agarose/polyacrylamide double-network (Li-AG/PAM DN) hydrogel electrolyte was synthesized by a heating-cooling and subsequent radiation-induced polymerization and cross-linking process. The Li-AG/PAM DN hydrogel electrolyte possesses extremely excellent mechanical properties with a compression strength of 150 MPa, a fracture compression strain of above 99.9%, a tensile strength of 1103 kPa, and an elongation at break of 2780%, greatly superior to those have been reported. It also achieves a high ionic conductivity of 41 mS cm originating from its interconnected three-dimensional porous network structure that provides a three-dimensional channel for ionic migration. Compared to the SC applying LiSO aqueous solution electrolyte, the corresponding flexible Li-AG/PAM DN hydrogel electrolyte-SC presents lower charge-transfer resistance, better ionic diffusion, being closer to ideal capacitive behaviors, superior rate capability, and better cycling stability, owing to the improved ionic transport in the Li-AG/PAM DN hydrogel electrolyte and electrode interfaces. Moreover, after testing with overcharge, short circuit, and high temperature, the capacitance of the Li-AG/PAM DN hydrogel electrolyte-SC can still be well maintained. Furthermore, the electrochemical properties of the Li-AG/PAM DN hydrogel electrolyte-SC remain almost intact under different compression strains/bending angles and even after 1000 compression/bending cycles. It is expected that the Li-AG/PAM DN hydrogel electrolyte may have broad applications in modern flexible and wearable electronics.

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