Aiming toward sustainability, poly-(itaconic acid) has been considered as an alternative to the widely used fossil-based poly-(acrylic acid). Its application has been, however, limited by its lower mechanical properties due to challenges in the polymerization processes. Herein, we report photopolymerizable and thermoreversible hydrogels based on poly-(itaconic acid) allowing tunability from high strength (∼1000 kPa) plastically yielding materials to soft elastomeric-like stretchability, also allowing thermoresponsive flow, and a relatively high water absorption of 384 g/g. The thermal gel melting stems from the dynamic covalent bonds, in combination with metal-ion-mediated supramolecular connections. The materials facilitate on-demand water stability while allowing gel-to-sol melting for thermal extrusion for 3D-printing, a combination not observed in classic permanent covalent networks. To promote sustainability, biosourceable starting materials are used without additional solvents or purification steps. Given the biocompatibility of the components, potential applications can be foreseen, such as tissue growth scaffolds, medical and hygienic superabsorbents, and tough hydrogels for soft robotics.

In biological systems, adaptive responses to environmental stimuli are facilitated by sensory transduction, where receptors transform stimuli into dynamic intermediate electrical signals for further processing. For bioinspired artificial systems, this suggests the need to develop concepts that transduce various stimuli into electrical intermediates for recognition. Inspired by biological magnetoreception in elasmobranchs, which sense magnetic environmental profiles for navigation, we introduce an artificial sensory transduction system for magnetic profile recognition of objects using electromagnetic induction to generate electrical intermediate signaling, coupled with machine learning for decoding. We design moldable magnetic soft composites (MSCs) comprising magnetic particles in a zwitterionic polymer matrix, encoding with both static (shape, rheology, and magnetization) and dynamic (magnetization decay) multidimensional features. Upon translocation through a receiving coil, MSCs generate distinct transient induced electrical signals. Machine learning algorithms decode the static and dynamic information with ∼100% and 87.5% recognition accuracy, respectively, with a recognition strength of 3 bits and a large information-carrying capacity of 1062-10934 possible encoded states. We suggest that electromagnetic induction in soft composites is a useful and generalizable concept for sensory transduction in emerging adaptive dissipative bioinspired materials, haptic systems, and soft robotics.

Functionalized particles ranging from nanoscale to microscale and their assemblies have facilitated a wide variety of sensing concepts, from molecular‐scale chemical and biological detection to large‐scale engineering defect testing. Related to macroscopic object shape sensing, visual recognition is generally the most versatile approach whenever possible. However, under certain conditions where visual perception is hindered, for example, dark space or underwater, electrosensing can serve as an alternative sensation manner. Inspired by this concept, the sensing of rudimentary object shapes using electrically conductive, soft ferromagnetic Ni particles is demonstrated, herein denoted as colloidal magnetoelectric shape recognition. By confining the target and sensory particles between two planar electrodes and using a magnetic field to drive the particles toward object edges, changes in electrical conductivity are monitored. Machine learning is then used to resolve the exact object shapes with high fidelity. This study introduces a colloidal magnetoelectric shape recognition strategy for short‐range shape sensing, with potential applications suggested for the fields such as soft robotics, drug delivery, and biomedical diagnostics.

Inspired by biological sensors that characteristically adapt to varying stimulus ranges, efficiently detecting stimulus changes sooner than the absolute stimulus values, we propose a mechanosensing concept in which the resolution can be adapted by magnetic field (H) gating to detect small pressure-changes under a wide range of compressive stimuli. This is realized with resistive sensing by pillared H-driven assemblies of soft ferromagnetic electrically conducting particles between planar electrodes under a voltage bias. By modulation of H, the pillars respond with mechanically adaptable sensitivity. Higher H enhances current resolution, while it increases scatter among repeating measurements due to increased magnetic structural jamming between colloids in their assembly. To manage the trade-off between electrical resolution and scatter, machine learning is introduced for searching optimum H gatings, thus facilitating efficient pressure prediction. This approach suggests bioinspired pathways for developing adaptive stimulus-responsive mechanosensors, detecting subtle changes across varying stimuli levels with enhanced effectiveness through machine learning.

Two-factor authentication (2FA) is widely used in informatics for identity verification and information encryption, yet its applications in materials science remain largely underexplored. In this study, a composite film composed of silica nanofibers (NFs) and fluorescent nanofibers (FNFs) is presented, offering a unique material-based approach to 2FA encryption. NFs and FNFs are synthesized via water-in-oil emulsions, resulting in films that can be both liquid- and light-responsive. NFs assembly exhibits intriguing light-scattering characteristics, rendering it opaque under normal conditions but transparent when wetted, functioning as a liquid-triggered optically shielding material. Embedded FNFs remain concealed within NF matrix, becoming fluorescently visible only under ultraviolet A (UVA) light illumination of specific wavelength. The encryption system requires two decryption keys - liquid and UVA light, which must be applied sequentially to successfully access the encoded information. Upon liquid exposure, the film transitions from opaque to transparent, allowing light transmission. Subsequent UVA irradiation reveals the hidden fluorescent patterns labeled by FNFs in film. This sequential encryption-decryption mechanism mimics the principles of 2FA in digital data systems, providing a promising new paradigm for secure information storage and transmission for patterns using material-based strategies.

Nature suggests concepts for materials with efficient mechanical energy storage and release, i.e., resilience, involving small energy dissipation upon mechanical loading and unloading, such as in resilin and elastin. These materials facilitate burst-like movements involving high stiffness and low strain and high reversibility. Synthetic hydrogels that allow highly reversible mechanical energy storage have remained a challenge, despite mimicking biological soft tissues. Here we show a synthetic concept using fixed hydrogel polymer compositions based on sequentially swollen and sequentially photopolymerized gelation steps for hierarchical networks. The sequential swellings facilitate the balance of properties between resilience and dissipation upon controlling of the chain extension. At low hierarchical levels, we show resilience with small hysteresis with increased stiffness and resilient energy storage, whereas at high hierarchical levels, a transition is shown to a dissipative and considerably reinforced state. The generality of this approach is shown using several photopolymerizable monomers.

High-haze materials have been widely used in optical and photonic applications, yet most exhibit fixed internal structures with static haze levels, limiting their adaptability across different usage scenarios. Here, we report a facile strategy to fabricate strain-dependent tunable high-haze films by blending silica nanofibers (NFs) into a polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) matrix. The composite SEBS/NF films exhibit increasing light scattering and haze with the NF content, reaching up to 94 %. Upon mechanical stretching, the absence of chemical bonding between the rigid NFs and flexible SEBS allows interfacial sliding, generating nanoscale cavities. These cavities significantly amplify the internal refractive index mismatch, leading to a reversible and strain-dependent enhancement of haze. In addition, the inherent hydrophobicity of SEBS promises environmental stability and anti-fouling properties, enabling robust performance in underwater conditions. Together, these features position the SEBS/NF films as promising candidates for multi-functional optical systems, including underwater light diffusers and adaptive light management devices.

Many biological tissues are mechanically strong and stiff but can still heal from damage. By contrast, synthetic hydrogels have not shown comparable combinations of properties, as current stiffening approaches inevitably suppress the required chain/bond dynamics for self-healing. Here we show a stiff and self-healing hydrogel with a modulus of 50 MPa and tensile strength up to 4.2 MPa by polymer entanglements in co-planar nanoconfinement. This is realized by polymerizing a highly concentrated monomer solution within a scaffold of fully delaminated synthetic hectorite nanosheets, shear oriented into a macroscopic monodomain. The resultant physical gels show self-healing efficiency up to 100% despite the high modulus, and high adhesion shear strength on a broad range of substrates. This nanoconfinement approach allows the incorporation of novel functionalities by embedding colloidal materials such as MXenes and can be generalized to other polymers and solvents to fabricate stiff and self-healing gels for soft robotics, additive manufacturing and biomedical applications.

In the August 7 issue of Science, Liu and colleagues report a co-crystallization strategy for inorganic-polymer hybrids and achieve ordered interfaces for the efficient coupling of mechanical, electrical, and magnetic responses. The resulting VSe2-PVDF magnetoelectric nanocomposites enable flexible, low-energy wearable sensors with ultrafast responses, high sensitivity, and exceptional performance.

While zwitterionic hydrogels and aq. polymers have already been used in, e.g., bio-related, environmental, and ionic transport-related applications, it is foreseen that their characteristic ability of zwitterions to bind functional particles combined with sol-gel transitions can allow emerging potential for responsive soft composites. Here, it is first shown that polyzwitterionic poly[2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (PDMAPS), allows organohydrogelation upon adding dimethyl sulfoxide to its aqueous solution, inducing phase-separations to form physical cross-links. Density functional theory (DFT) analysis reveals solvent-polymer interactions that drive the organohydragelation. The organohydrogels exhibit ultrahigh stretchability (>2800%), quick self-adhesion, remoldability, and tunable viscoelasticity. By modulating solvent composition and integrating functional fillers, distinct sol- and gel-like states are achieved on-demand. In the sol-like state, titanium carbide nanosheets (MXenes)-incorporated PDMAPS soft composite enable mechano-tunable electromagnetic interference shielding via nanosheet reorientation under strain. In the gel-like regime, incorporation of magneticneodymium iron boron magnet (NdFeB) microparticles yields mechano-magneto-electric transducers for strain detection, dynamic haptic functionality, as demonstrated by Morse code encoding, and high durability in repeated compressive cycles. This work introduces a versatile organohydrogel platform with tunable viscoelastic properties, suitable for on-demand functionalized soft composites, suggesting new design principles for transducing, sensing, and soft robotics.

Energy- and resource-efficient electrocatalytic water splitting is of paramount importance to enable sustainable hydrogen production. The best bulk catalyst for the hydrogen evolution reaction (HER), i.e., platinum, is one of the scarcest elements on Earth. The use of raw material for HER can be dramatically reduced by utilizing nanoclusters. In addition, nanoalloying can further improve the performance of these nanoclusters. In this paper, we present results for HER on nanometer-sized ligand-free AuPt nanoclusters grafted on carbon nanotubes. These results demonstrate excellent monodispersity and a significant reduction of the overpotential for the electrocatalytic HER. We utilize atomistic machine learning techniques to elucidate the atomic-scale origin of the synergistic effect between Pt and Au. We show that the presence of surface Au atoms, known to be poor HER catalysts, in a Pt(core)/AuPt(shell) nanocluster structure, drives an anomalous enhancement of the inherently high catalytic activity of Pt atoms.

Stimuli-responsive hydrogels with thermal phase transitions serve as pivotal components in advancing biomedical and soft robotics applications. In contrast to widely studied LCST-type thermo-responsive hydrogels, UCST-type hydrogels provide reverse thermo-responses. However, conventional UCST-type hydrogels suffer from weak mechanical properties and fixed phase transition kinetics. Here, we present polyzwitterionic UCST-type hydrogels under coplanar nanoconfinement by large aspect ratio hectorite nanosheets. The nanoconfinement significantly enhances the strength and stiffness of the hydrogels. In addition, the nanosheets serve as kinetic barriers for water diffusion. This regulates the swelling and shrinking kinetics of the polyzwitterionic hydrogels and thus allows for tunable phase transitions dependent on the thermal history of the hydrogels. Furthermore, we demonstrate that the incorporation of gold nanoparticles allows precise control of the optical properties of the hydrogel through photothermal means. These findings pave the way for engineering both the mechanical and thermoresponsive properties in polyzwitterionic hydrogels, thus broadening their applications in smart soft materials.

Electrostatic flocking, traditionally used in decoration, has recently found emerging applications in diverse fields such as sensors, tissue engineering, evaporators and thermal management. By attaching high aspect ratio fibers onto a substrate through electrostatic flocking, it enables large‐scale control of fiber orientation, resulting in fibrous, porous, or furry structures with several benefits, including enhanced microforce detection sensitivity, large specific surface area, improved reflection/absorption, increased surface roughness, anisotropic surfaces, and strengthened mechanical properties. While challenges remain in achieving highly customized pattern for functional materials, electrostatic flocking holds promise in replicating natural fluffy structures, such as villi and cilia, which could lead to superior performance in biomimetic and functional applications. Despite recent significant progress, a comprehensive review on this technology for cutting‐edge applications is still lacking. This review aims to provide an in‐depth analysis of electrostatic flocking's broader applications and investigates the potential future of electrostatic flocking at the forefront of functional materials by examining the relationship between structure and performance in advanced materials. It begins with an overview of the technology's principles, followed by an exploration of its applications and morphological advantages, and concludes with a discussion of challenges, material selection, structural design, and future directions for this innovative technology.

Anti-inflammatory M2 macrophages are highly relevant in various physiological processes ranging from tissue regeneration to cancer progression. However, conventional two-dimensional (2D) in vitro cell cultures limit our understanding of macrophage phenotypes and how they can be modulated for immunotherapeutic approaches. Moreover, there is a growing demand for scalable, animal-free hydrogels to replace animal-derived materials in three-dimensional (3D) in vitro models. In this study, we explore hydrogels based on plant-derived nanofibrillar cellulose (NFC), also known as cellulose nanofibrils (CNFs) or microfibrillated cellulose (MFC), for generating 3D in vitro models of M2-like macrophages from human blood monocytes. Notably, flow cytometry analysis shows that cells cultured in 3D phosphorylated NFC hydrogels show enhanced expression of the M2 macrophage marker CD206 compared to cells cultured in other negatively charged hydrogels prepared from native NFC or NFCs with carboxylate or sulfate modifications. Furthermore, the upregulation of CD206 expression in 3D phosphorylated NFC is comparable to the induction of CD206 in interleukin 4 (IL-4)-differentiated M2a macrophages. In addition, the cells in the phosphorylated NFC hydrogel show a differential cytokine profile compared to 2D cultured cells, secreting similar levels of tumor necrosis factor α (TNF-α), but 2.6-fold higher amounts of IL-1β and 1.2-fold higher amounts of IL-10. The results suggest that the conversion of monocytes to M2-like macrophages can be controlled by the phosphorylation of NFC, a strategy which does not require the addition of polarization factors like growth factors and cytokines conventionally used to generate macrophages in vitro. The findings highlight the importance of surface chemistry in matrix-guided macrophage polarization, paving the way for xeno-free yet bioactive 3D macrophage culture scaffolds for immunological research.

Living tissues possess synergistic mechanical properties that facilitate specific functions. Unlike toughening allowed by promoted mechanical energy dissipation, by contrast, dissipation is minimized for mechanical energy storage and efficient release, such as facilitating animal jumping. Nature shows such resilient materials, e.g., resilin, and elastin, characteristically involving small strain with high stiffness. Such properties have rarely been achieved in synthetic hydrogels, even if hydrogels are considered analogous to living soft tissue. We show bioinspired resilient hydrogels with high energy storage at small strains and high stiffness upon repeated hydrogel swellings in mixtures of monomers, crosslinkers and water with subsequent photopolymerizations up to 7 hierarchical levels N. Towards higher N, the chains are progressively more coiled and entangled around the stretched chains of lower N, leading to hierarchical swelling. By controlling N, the approach allows to surpass even biological proteins for efficient energy storage. We show generality and application potential for soft robot jumpers.

Converting lignin into useful colloidal entities with uniform size and shape offers exciting opportunities for utilization; however, this endeavor requires overcoming challenges caused by structural heterogeneity and gaining further understanding to exploit its unique functional possibilities. Still, colloidal lignin has already provided new insights into bio-polymeric materials and has triggered various innovative applications that have inspired the scientific community. This review aims to provide a comprehensive discussion of the current understanding of colloidal lignin and its emergent applications. First, a fundamental overview of lignin, including its chemistry and processing is provided. Subsequently, a multitude of technical routes to tune the properties of colloidal lignin using nano-/micro-fabrication approaches to control macroscale properties is presented. Thereafter, examples of innovative material technologies based on colloidal lignin in areas such as pollution remediation, polymeric materials, macromolecular materials, and drug delivery are given. Finally, open challenges and suggestions for future research will be discussed to guide future research to rationally expand the portfolio of promising lignin-based technologies.

Biological tissues, such as tendons or cartilage, possess high strength and toughness with very low plastic deformations. In contrast, current strategies to prepare tough hydrogels commonly utilize energy dissipation mechanisms based on physical bonds that lead to irreversible large plastic deformations, thus limiting their load-bearing applications. This article reports a strategy to toughen hydrogels using fibrillar connected double networks (fc-DN), which consist of two distinct but chemically interconnected polymer networks, that is, a polyacrylamide network and an acrylated agarose fibril network. The fc-DN design allows efficient stress transfer between the two networks and high fibril alignment during deformation, both contributing to high strength and toughness, while the chemical crosslinking ensures low plastic deformations after undergoing high strains. The mechanical properties of the fc-DN network can be readily tuned to reach an ultimate tensile strength of 8 MPa and a toughness of above 55 MJ m-3, which is 3 and 3.5 times more than that of fibrillar double network hydrogels without chemical connections, respectively. The application potential of the fc-DN hydrogel is demonstrated as load-bearing damping material for a jointed robotic lander. The fc-DN design provides a new toughening mechanism for hydrogels that can be used for soft robotics or bioelectronic applications.

In colloids, the shape influences the function. In silica, straight nanorods have already been synthesized from water-in-oil emulsions. By contrast, curly silica nanofibers have been less reported because the underlying growth mechanism remains unexplored, hindering further morphology control for applications. Herein, we describe the synthetic protocol for silica nanofibers with a tunable curliness based on the control of the water-in-oil emulsion droplets. Systematically decreasing the droplet size and increasing their contact angle, the Brownian motion of the droplets intensifies during the silica growth, thus increasing the random curliness of the nanofibers. This finding is supported by simplistic theoretical arguments and experimentally verified by varying the temperature to finely tune the curliness. Assembling these nanofibers toward porous disordered films enhances multiple scattering in the visible range, resulting in increased whiteness in contrast to films constructed by spherical and rod-like building units, which can be useful for, e.g., coatings and pigments.