The dehydration process is widely recognized as a significant phenomenon in nature. Hydrogels, which are important functional materials with high water content and crosslinked networks, encounter the issue of dehydration in their practical applications. Here, we report the distinctive anisotropic dehydration modality of dynamic hydrogels, which is fundamentally different from the more commonly observed isotropic dehydration of covalent hydrogels. Xerogels derived from dynamic hydrogel dehydration will fully cover a curved substrate surface and exhibit hollow structures with internal knots, in contrast to the bulk xerogels produced by covalent hydrogel dehydration. Depending on the competing cohesion of polymer chains and the adhesion at the hydrogel-substrate interface, the previously overlooked reorganization of polymer networks within dynamic hydrogels, triggered by dehydration-induced stress, has been discovered to regulate such macroscopic structural reconstruction for dynamic hydrogel dehydration. With the attached hydrogel-substrate interface, the surface microstructures of substrates can also be engraved onto xerogels with high resolution and on a large scale. This work will greatly enhance our understanding of the soft matter dehydration process and broaden the applications of dehydration technologies using water-containing materials.

Intelligent hydrogels responsive to external stimuli have been widely studied due to their great potentials for applications in artificial muscles, soft robotics, sensors and actuators. However, the weak mechanical properties, narrow response range, and slow response speed of many responsive hydrogels have hindered practical applications. In this paper, tough multi-responsive hydrogels were synthesized by using vinyl-functionalized triblock copolymer micelles as macro-crosslinkers and N-isopropyl acrylamide (NIPAM) and acrylamide (AAm) or 2-(dimethylamino)ethyl methacrylate (DMAEMA) and 2-acrylamido-2-methyl-1-propane-sulfonic acid (AMPS) as monomers. The P(NIPAM-co-AAm) hydrogels presented tensile strength of up to 1.6 MPa and compressive strength of up to 127 MPa and were tunable by changing their formulations. Moreover, the lower critical solution temperature (LCST) of the thermosensitive hydrogels was manipulated in a wide range by changing the molar ratio of NIPAM to AAm. Responsive hydrogel bilayers were fabricated through a two-step synthesis. A second layer of P(DMAEMA-co-AMPS) was synthesized on the first P(NIPAM-co-AAm) layer to obtain a bilayer hydrogel, which was responsive to temperature, pH and ionic strength changes to undergo fast and reversible shape transformation in a few minutes. This kind of strong and tough multi-responsive hydrogel device has broad prospects in soft actuators.

Since the emergence of triboelectric nanogenerators (TENGs), new strategies, materials, and applications have been rapidly developed in the past few years to realize the efficient utilization of mechanical energy from the environment. In the pursuit of high performance, long‐term stability, and adaption in a comprehensive situation, it is necessary to fully understand the triboelectric effect and its related parameters by analyzing real‐time working status of TENG devices. This review focuses on the interface structures in TENG devices and the real‐time charge transfer process enhanced by the microstructures/nanostructures on dielectric layer surfaces, which are believed to be primely important in addition to the inherent properties of materials. Four modes of TENG operations, two main types interfaces as solid–solid interface and solid–liquid interface, as well as various materials used for device fabrication are discussed initially. Based on the real‐time working status, the interface structures of TENG devices are classified into three different groups as one‐dimensional, two‐dimensional, and three‐dimensional ones. In addition, the noncontact mode TENG devices are also described and are regarded as candidates for mechanical wear. Finally, existing challenges and the prospect of TENG devices based on the structural design of interfaces are summarized.

Continuous passive motion (CPM) is an adjunct therapy to the standard postoperative rehabilitation regimen of joint injuries. The capability of real-time monitoring actual bending angle of knee joints is highly desired for treatment strategies of personalized postoperative rehabilitation and telemedicine. Here we report an intelligent CPM system for personalized rehabilitation and telemedicine based on the flexible and versatile ionotronic that possesses impressive mechanical properties (2.56 MPa tensile strength; 11.63 MJ m⁻³ toughness), fast self-recovery ability (60 s) and broaden environmental tolerance (−60–45 °C). Especially, the ionotronic responds fast and shows stability for cyclic strain sensing, ensuring the detection of actual joint bending angle with high sensitivity and reliability. The intelligent CPM system assembled with this ionotronic and a wireless transmitter was constructed, opening up a horizon for developing digital intelligent medical that can remotely monitor the movement of hospitalized/at-home patients who use CPM for personalized postoperative rehabilitation.