Xiaozhuang Zhou

Muscles are highly anisotropic, force‐bearing issues. They form via a process involving nutrient absorption for matrix growth and mechanical training for matrix toughening, in which cyclic disassembly‐reconstruction of muscle fibers plays a critical role in generating strong anisotropic structures. Inspired by this process, a mechanical training‐associated growing strategy is developed for preparing tough anisotropic hydrogels. Using anisotropic hydrogels made from polyvinyl alcohol (PVA)/tannic acid (TA) as an example, it is demonstrated that the hydrogels can absorb poly(ethylene glycol) diacrylate (PEGDA) via disassembling their aligned nanofibrillar structures. Incorporation of PEGDA within the hydrogels induces PVA to form crystal domains while subsequent mechanical training can restore the aligned fibrillar structures. Such a combining process results in expansion in materials’ size (≈2 times) and significant enhancement in their mechanical properties (Young's modulus: from 2.4 to 2.85 MPa; ultimate tensile strength: from 8.2 to 14.1 MPa; toughness: from 335 to 465 MJ m⁻³). With a high energy dissipation efficiency (≈90%), potential applications for these tough and adaptable hydrogels are envisioned in impact‐protective materials, surgical sutures, etc.

This study presents the theoretical design and evaluation of a triple-junction polymer solar cell architecture, incorporating oligomers of PDCBT, PPDT2FBT, and PDPP3T as donor materials and PC₇₁BM as the electron acceptor. Using density functional theory (DFT) simulations and time-dependent DFT (TD-DFT) methods, the investigation covers essential photovoltaic parameters, including molecular geometries, UV-Vis spectra, and charge transport properties. The device is structured to maximize solar energy absorption across the spectrum, featuring front, middle, and back junctions with band gaps of 1.9 eV, 1.63 eV, and 1.33 eV, respectively. Each layer targets different regions of the solar spectrum, optimizing light harvesting and charge separation. This innovative multi-junction design offers a promising pathway to enhanced power conversion efficiencies in polymer solar cells, advancing the integration of renewable energy technologies.

Additive manufacturing of transition metal sulfides (TMS) enables the creation of complex 3D structures, significantly expanding their applications. However, preparing 3D‐structured TMS remains challenging due to difficulties in developing suitable inks. In this study, a supramolecular micelle hydrogel as the ink to fabricate 3D‐structured TMS is utilized. Initially, the hydrogels are printed and infused with metal salt solutions to stabilize the structures, which are then calcined to convert into miniaturized 3D‐TMS replicas. The micellar hydrogels crosslink via hydrophobic interactions, with sodium dodecyl sulfonate (SDS) micelles providing both a hydrophobic environment and sulfur sources. During calcination, the decomposed sulfur precursors coordinate with metal ions to form various TMS, including FeS₂, Cu₂S, Ni₃S₂, and Co₉S₈, along with several metal sulfides like PbS and SnS. Additionally, the method also allows for the preparation of transition metal dichalcogenides such as MoS₂ and WS₂. The formation mechanism is demonstrated using Ni₃S₂ as an example which exhibits notable catalytic activity in oxygen evolution reactions (OER) and hydrogen evolution reactions (HER). Given its simplicity and versatility, this dynamic micellar hydrogel‐derived strategy offers a promising pathway for creating advanced TMS materials.

Vitrimers are reprocessing and recycling thermosetting plastics. They possess reconfigurable polymer networks that allow for unlimited transformation in shape in principle. However, current strategies to reshape the vitrimers typically involve heat or light, which often induces undesirable oxidation and decomposition. To address this issue, here a water‐assisted approach is proposed for programming epoxy vitrimers’ shapes. In this design, water molecules are utilized to reversibly dissociate the hydrogen bonds in epoxy vitrimers to enable the polymer segments to move flexibly. The hydrated epoxy vitrimers can then be reprogrammed and retained into different temporary shapes by removing the water. Such samples would be recovered to their original shapes by rehydration, exhibiting water‐induced shape memory property. More than temporary deformation, the permanent figures of the hydrated vitrimers can also be permanently changed at room temperature (rt) or elevated temperatures in the presence of transesterification catalysts. Combing the shape memory and high temperature plasticity or utilizing rt plasticity, sophisticated shapes such as spiral shapes are demonstrated. It is envisioned that this water‐assisted methodology can be useful in programming cross‐linked polymers into diverse 3D structures, which has wide practical applications in soft robots, deployable devices, aerospace materials, etc.

Growth constitutes a powerful method to post-modulate materials’ structures and functions without compromising their mechanical performance for sustainable use, but the process is irreversible. To address this issue, we here report a growing-degrowing strategy that enables thermosetting materials to either absorb or release components for continuously changing their sizes, shapes, compositions, and a set of properties simultaneously. The strategy is based on the monomer-polymer equilibrium of networks in which supplying or removing small polymerizable components would drive the networks toward expansion or contraction. Using acid-catalyzed equilibration of siloxane as an example, we demonstrate that the size and mechanical properties of the resulting silicone materials can be significantly or finely tuned in both directions of growth and decomposition. The equilibration can be turned off to yield stable products or reactivated again. During the degrowing-growing circle, material structures are selectively varied either uniformly or heterogeneously, by the availability of fillers. Our strategy endows the materials with many appealing capabilities including environment adaptivity, self-healing, and switchability of surface morphologies, shapes, and optical properties. Since monomer-polymer equilibration exists in many polymers, we envision the expansion of the presented strategy to various systems for many applications.

Polymer electrolytes (PEs) are a promising alternative to overcome shortcomings of conventional lithium ion batteries (LiBs) and make them safer for users. Introduction of self-healing features in PEs additionally leads to prolonged life-time of LIBs, thus tackling cost and environmental issues. We here present solvent free, self-healable, reprocessable, thermally stable, conductive poly(ionic liquid) (PIL) consisting of pyrrolidinium-based repeating units. PEO-functionalized styrene was used as a co-monomer for improving mechanical properties and introducing pendant OH groups in the polymer backbone to act as a transient crosslinking site for boric acid, leading to the formation of dynamic boronic ester bonds, thus forming a vitrimeric material. Dynamic boronic ester linkages allow reprocessing (at 40 °C), reshaping and self-healing ability of PEs. A series of vitrimeric PILs by varying both monomers ratio and lithium salt (LiTFSI) content was synthesized and characterized. The conductivity reached 10⁻⁵ S cm⁻¹ at 50 °C in the optimized composition. Moreover, the PILs rheological properties fit the required melt flow behavior (above 120 °C) for 3D printing via fused deposition modeling (FDM), offering the possibility to design batteries with more complex and diverse architectures.

Electro-responsive dynamic hydrogels, which possess robust mechanical properties and precise spatiotemporal resolution, have a wide range of applications in biomedicine and energy science. However, it is still challenging to design and prepare electro-responsive hydrogels (ERHs) which have all of these properties. Here, we report one such class of ERHs with these features, based on the direct current voltage (DCV)-induced rearrangement of sodium dodecyl sulfate (SDS) micelles, where the rearrangement can tune the hydrogel networks that are originally maintained by the SDS micelle-assisted hydrophobic interactions. An enlarged mesh size is demonstrated for these ERHs after DCV treatment. Given the unique structure and properties of these ERHs, hydrophobic cargo (thiostrepton) has been incorporated into the hydrogels and is released upon DCV loading. Additionally, these hydrogels are highly stretchable (>6000%) and tough (507 J/m²), showing robust mechanical properties. Moreover, these hydrogels have a high spatiotemporal resolution. As the cross-links within our ERHs are enabled by the non-covalent (i.e., hydrophobic) interactions, these hydrogels are self-healing and malleable. Considering the robust mechanical properties, precise spatiotemporal resolution, dynamic nature (e.g., injectable and self-healing), and on-demand drug delivery ability, this class of ERHs will be of great interest in the fields of wearable bioelectronics and smart drug delivery systems.

Shear-thickening materials have been widely applied in fields related to smart impact protection due to their ability to absorb large amounts of energy during sudden shock. Shear-thickening materials with multifunctional properties are expanding their applications in wearable electronics, where tactile sensors require interconnected networks. However, current bifunctional shear-thickening cross-linked polymer materials depend on supramolecular networks or slightly dynamic covalently cross-linked networks, which usually exhibit lower energy-absorption density than the highly dynamic covalently cross-linked networks. Herein, we employed boric ester-based covalent adaptive networks (CANs) to elucidate the shear-thickening property and the mechanism of energy dissipation during sudden shock. Guided by the enhanced energy-absorption capability of double networks and the requirements of the conductive networks for the wearable tactile sensors, tungsten powders (W) were incorporated into the boric ester polymer matrix to form a second network. The W networks make the materials stiffer, with a 13-fold increase in Young's modulus. Additionally, the energy-absorption capacity increased nearly 7 times. Finally, we applied these excellent energy-absorbing and conductive materials to bifunctional shock-protective and strain rate-dependent tactile sensors. Considering the self-healable and recyclable properties, we believe that these anti-impact and tactile sensing materials will be of great interest in wearable devices, smart impact-protective systems, post-tunable materials, etc.