Ultrafast underwater self-healing piezo-ionic elastomer via dynamic hydrophobic-hydrolytic domains

Reproducible Transpalpebral Intraocular Pressure Sensing Enabled by Low-Energy-Barrier Ion Pumping

Elevated intraocular pressure (IOP) is a major risk factor for blindness in glaucoma patients, highlighting the critical need for continuous IOP monitoring. While traditional transpalpebral tonometers (TTs) circumvent corneal contact by adopting Goldmann applanation principles through impulsive corneal flattening forces, their measurement accuracy is inherently compromised by eyelid-induced cushion effects. In contrast, parallel-plate capacitive sensors employ constant compressive loading upon the eyelid, achieving palpebral compaction to mitigate the cushion effects. More recently, ion-pump-based capacitive sensors have emerged as promising alternatives, particularly due to their enhanced sensitivity. Nevertheless, these sensors exhibit sharp sensitivity deterioration at extended measurement ranges (0-10 kPa). This operational constraint originates from the strong hydrogen bond energies (between confining matrices and ions) and rigid block copolymer matrices' steric hindrance. To address these limitations, we developed a transpalpebral tonometer featuring low-energy-barrier ion pumps, incorporating (3-aminopropyl)triethoxysilane (APTES)-silanized liquid metal nanoparticles (LM NPs) as confining matrices and an ionic liquid as an ion donor. The low-energy barrier arises from (1) weaker hydrogen bonds between the N-H of APTES and the F of the ionic liquid and (2) reduced crystallinity in the elastomeric matrices induced by LM NPs. Our sensor achieves a sensitivity of 24.88 kPa-1 with maintained linearity over 0-85 kPa. In vivo animal trials over 120 min validated its continuous IOP monitoring capability, reliably detecting elevated IOP states and demonstrating clinical potential for glaucoma management.

Underwater self-healing and highly stretchable nano-cellulose composite hydrogels based on dipole-dipole interactions for a "smart" plugging in CO2 flooding

The development of hydrogels with water resistance, superb self-healing and mechanical performance that can adapt to the reservoir conditions to plug CO₂ channeling in reservoirs has a significant potential to boost the enhanced oil recovery and CO2 geo-sequestration. Herein, we present underwater self-healing and highly stretchable nano-cellulose composite hydrogels for plugging in CO2 flooding via in situ polymerization of acrylonitrile (AN) based solution with carboxyl-grafted nanocellulose (TOCNF) and tannic acid (TA), which exhibited a Young's modulus of 1.1 MPa, a stretchability of 1624 % and a toughness of 13.22 MJ/m3. The presence of dipole-dipole interactions between the CN groups of the copolymer chains endowed this gel with excellent underwater repair with 98.9 % self-healing efficiency within 48 h. In the artificial porous media, the PAMN-TA-TOCNF systems (including the in-situ gel and the preformed particle gel) demonstrated remarkable efficacy and renewable plugging performance, which is attributed to their pore-scale remigrating behaviour (i.e., capture, healing-to-trapping, elastic deformation, and frictional migration). This "smart" gel could provide an environment-friendly and remarkably economic (no disposable) alternative to the current state of the CO2 plugging project in oilfields.

Flexible Waterborne Silicone-Based Coating with High Mechanical, Stretchable, and Durable Antismudge Properties

Eco-friendly, flexible, and fluorine-free antismudge coatings have broad applications in soft substrates such as fabrics, premium leather, synthetic leather, and flexible electronic devices. However, developing antismudge coatings possessing both excellent durability and desirable softness and stretchability remains a formidable challenge. Herein, two waterborne silicone-based emulsions were prepared via emulsion inversion point method, using high-molecular-weight divinyl-terminated poly(dimethylsiloxane) (ViPDMSVi) and methyl vinyl MQ resin as raw materials, respectively, with polyether-modified silicone (D(PDMS)PE) compounding with sodium dodecyl sulfate (SDS) as emulsifiers. Subsequently, poly(methylhydrosiloxane) emulsion (PHSE) was utilized as a cross-linking agent, and a highly comprehensive waterborne silicone-based coating was successfully fabricated through hydrosilylation among the three types of emulsions. Owing to rational structural design and aqueous-based strategy, the coating achieves the integration of high mechanical properties (≥3.5 MPa tensile strength and 214% elongation) and stretchability, outstanding flexibility (the glass transition temperature below -105 °C), high transparency, excellent self-cleaning, and antismudge performance. Moreover, the exceptional durability of the coating is evidenced by maintaining antismudge properties after rigorous treatments, such as 24 h of UV irradiation, immersion in acid, alkali, and salt solutions for 24 h, 500 cycles of mechanical abrasion under a load of 1000 g, etc. This work provides a feasible pathway for manufacturing high-performance antismudge coatings suitable for soft substrates in a green and sustainable manner.

Skin-like Heterogeneous and Self-Healing Conductive Hydrogel toward Ultrasensitive Marine Sensing

Flexible wearable electronic devices based on hydrophobic, conductive hydrogels have attracted widespread attention in the field of underwater sensing. However, traditional homogeneous hydrogels tend to compromise their conductivity and sensing performance when achieving hydrophobicity, and the high complexity of marine environments further reduces their sensing performance and service life. Here, we develop a seawater-resistant conductive hydrogel with ultrahigh sensitivity and self-healing ability by the introduction of a skin-like heterogeneous structure, consisting of a hydrophobic outer layer that protects against seawater and a conductive internal layer that senses. Based on a heterogeneous structure obtained through surface hydrophobic modification of confined nitrogen-alkylation reaction, the conductive hydrogel simultaneously achieves satisfying seawater resistance (contact angle of 123.2°), high ionic conductivity (2.86 S m-1), and excellent sensing sensitivity in seawater (GF = 6.15), harmonizing the contradiction between water resistance and sensing of traditional hydrophobic hydrogels. In addition, abundant hydrogen-bonding and dipole-dipole interactions endow the heterogeneous hydrogel with an outstanding self-healing ability, exhibiting high-efficiency self-healing behavior in seawater. Underwater strain sensors constructed with the heterogeneous hydrogel can be used for detecting human motion in simulated seawater environments and real-time signal transmission, showcasing their great potential as wearable electronic devices in the marine sensing field.

Progress and Perspectives in 2D Piezoelectric Materials for Piezotronics and Piezo-Phototronics

The emergence of two-dimensional (2D) materials has catalyzed significant advancements in the fields of piezotronics and piezo-phototronics, owing to their exceptional mechanical, electronic, and optical properties. This review provides a comprehensive examination of key 2D piezoelectric and piezo-phototronic materials, including transition metal dichalcogenides, hexagonal boron nitride (h-BN), and phosphorene, with an emphasis on their unique advantages and recent research progress. The underlying principles of piezotronics and piezo-phototronics in 2D materials is discussed, focusing on the fundamental mechanisms which enable these phenomena. Additionally, it is analyzed factors affecting piezoelectric and piezo-photoelectric properties, with a particular focus on the intrinsic piezoelectricity of 2D materials and the enhancement of out-of-plane polarization through various modulation techniques and materials engineering approaches. The potential applications of these materials are explored from piezoelectric nanogenerators to piezo-phototronic devices and healthcare. This review addresses future challenges and opportunities, highlighting the transformative impact of 2D materials on the development of next-generation electronic, optoelectronic, and biomedical devices.

Autonomous self-healing and superior tough polyurethane elastomers enabled by strong and highly dynamic hard domains

Self-healing materials show exceptional application potential for their high stability and longevity. However, a great challenge of the application of self-healing materials is the tradeoff between mechanical robustness and room temperature self-healing. In order to address this tradeoff, inspired by the characteristic that small molecules of living organisms self-assemble into large protein molecules by non-covalent interactions, we constructed polyurethane with highly dynamic and strong hard domains composed of dense hydrogen bonds and π-π interactions between the phenylurea groups at the end of the side chain. The prepared elastomer (PU-HU2-60) exhibits exceptional tensile performance (tensile strength is 18.27 MPa and ultimate elongation is 904.6%) and crack tolerance (fracture energy is 57.78 kJ m-2), surpassing those of most room temperature self-healing materials. After being damaged, the dynamic change process of hydrogen bonds and π-π interactions enables the elastomer to show a high self-healing efficiency of 92.15% at room temperature. Using molecular dynamics (MD) simulations and experiments, we verified that hydrogen bonds and π-π interactions promote the formation of hard domains and the autonomous self-healing of elastomers. The prepared elastomers can also be recycled and they showed ultra-high and restorable adhesion between metals. This work demonstrates a new strategy to balance the mechanical and self-healing properties of elastomers to expand their practical applications such as metal adhesives.

Bio-Inspired Neuromorphic Sensory Systems from Intelligent Perception to Nervetronics

Inspired by the extensive signal processing capabilities of the human nervous system, neuromorphic artificial sensory systems have emerged as a pivotal technology in advancing brain-like computing for applications in humanoid robotics, prosthetics, and wearable technologies. These systems mimic the functionalities of the central and peripheral nervous systems through the integration of sensory synaptic devices and neural network algorithms, enabling external stimuli to be converted into actionable electrical signals. This review delves into the intricate relationship between synaptic device technologies and neural network processing algorithms, highlighting their mutual influence on artificial intelligence capabilities. This study explores the latest advancements in artificial synaptic properties triggered by various stimuli, including optical, auditory, mechanical, and chemical inputs, and their subsequent processing through artificial neural networks for applications in image recognition and multimodal pattern recognition. The discussion extends to the emulation of biological perception via artificial synapses and concludes with future perspectives and challenges in neuromorphic system development, emphasizing the need for a deeper understanding of neural network processing to innovate and refine these complex systems.

Cilia-Inspired Bionic Tactile E-Skin: Structure, Fabrication and Applications

The rapid advancement of tactile electronic skin (E-skin) has highlighted the effectiveness of incorporating bionic, force-sensitive microstructures in order to enhance sensing performance. Among these, cilia-like microstructures with high aspect ratios, whose inspiration is mammalian hair and the lateral line system of fish, have attracted significant attention for their unique ability to enable E-skin to detect weak signals, even in extreme conditions. Herein, this review critically examines recent progress in the development of cilia-inspired bionic tactile E-skin, with a focus on columnar, conical and filiform microstructures, as well as their fabrication strategies, including template-based and template-free methods. The relationship between sensing performance and fabrication approaches is thoroughly analyzed, offering a framework for optimizing sensitivity and resilience. We also explore the applications of these systems across various fields, such as medical diagnostics, motion detection, human-machine interfaces, dexterous robotics, near-field communication, and perceptual decoupling systems. Finally, we provide insights into the pathways toward industrializing cilia-inspired bionic tactile E-skin, aiming to drive innovation and unlock the technology's potential for future applications.

Polypropylene Blends with Durable Hydrophobicity and Enhanced Mechanical Properties Based on POSS and Alkane Modified Polypentafluorophenyl Methacrylate

Durable functionalization on polypropylene (PP) surfaces is always a key problem to besolved. Coatings with low surface energy peel off easily especially under extreme conditions, owing to their weak adhesion. In this paper, side groups of both polyhedral oligomeric silsesquioxane (POSS) and alkane are grafted to polypentafluorophenyl methacrylate (PFP), and then PP blends with these side-group modified PFP are obtained through a melt-blending process. It is found that POSS can result in surface segregation and provide hydrophobicity in blends. Microfibers are formed because of the orientation effect during the tensile testing, which furtherly promotes mechanical strength. Significantly, alkaneside-groups can be entangled with PP segments, which brings about cross linking. Therefore, with crosslinking and synchronous orientation of POSS, the elongation at the break of blends is greatly increased up to 974%. The final blend demonstrates quite durable hydrophobicity under many extreme conditions, such as repeated tape peeling, ultrasonic washing, strong friction, and soaking in strong acid (pH = 1), strong alkali (pH = 14) and alcohol. The heat and UV resistance of the blend are also obviously improved. This study will develop anovel and facile strategy to endow PP with durable hydrophobicity as well as greatly enhanced mechanical properties.

A Versatile Microporous Design toward Toughened yet Softened Self-Healing Materials

Realizing the full potential of self-healing materials in stretchable electronics necessitates not only low modulus to enable high adaptivity, but also high toughness to resist crack propagation. However, existing toughening strategies for soft self-healing materials have only modestly improves mechanical dissipation near the crack tip (ГD), and invariably compromise the material's inherent softness and autonomous healing capabilities. Here, a synthetic microporous architecture is demonstrated that unprecedently toughens and softens self-healing materials without impacting their intrinsic self-healing kinetics. This microporous structure spreads energy dissipation across the entire material through a bran-new dissipative mode of adaptable crack movement (ГA), which substantially increases the fracture toughness by 31.6 times, from 3.19 to 100.86 kJ m-2, and the fractocohesive length by 20.7 times, from 0.59 mm to 12.24 mm. This combination of unprecedented fracture toughness (100.86 kJ m-2) and centimeter-scale fractocohesive length (1.23 cm) surpasses all previous records for synthetic soft self-healing materials and even exceeds those of light alloys. Coupled with significantly enhanced softness (0.43 MPa) and nearly perfect autonomous self-healing efficiency (≈100%), this robust material is ideal for constructing durable kirigami electronics for wearable devices.

Ultrathin Self-Healing Nanofibrous Membrane with a Hierarchical Confined Structure for Biomimetic Epidermal Electrodes

Integrating self-healing capabilities into epidermal electrodes is crucial to improving their reliability and longevity. Self-healing nanofibrous materials are considered an ideal candidate for constructing ultrathin, long-lasting wearable epidermal electrodes due to their lightweight and high breathability. However, due to the strong interaction between fibers, self-healing nanofiber membranes cannot exist stably. Therefore, the development of self-healing and breathable nanofibrous epidermal electrodes still remains a major challenge. Here, a hierarchical confinement strategy that combines molecular and spatial confinement to overcome supramolecular hydrogen bonding between self-healing nanofibers is reported, and an ultrathin self-healing nanofibrous epidermal electrode with a neural net-like structure is developed. It can achieve real-time monitoring of electrophysiological signals through long-term conformal attachment to skin or plants and has no adverse effects on skin health or plant growth. Given the almost imperceptible nature of epidermal electrodes to users and plants, it lays the foundation for the development of biocompatible, self-healing, wearable, flexible electronics.

Self-Healing Materials for Bioelectronic Devices

Though the history of self-healing materials stretches far back to the mid-20th century, it is only in recent years where such unique classes of materials have begun to find use in bioelectronics-itself a burgeoning area of research. Inspired by the natural ability of biological tissue to self-repair, self-healing materials play a multifaceted role in the context of soft, wireless bioelectronic systems, in that they can not only serve as a protective outer shell or substrate for the internal electronic circuitry-analogous to the mechanical barrier that skin provides for the human body-but also, and most importantly, act as an active sensing safeguard against mechanical damage to preserve device functionality and enhance overall durability. This perspective presents the historical overview, general design principles, recent developments, and future outlook of self-healing materials for bioelectronic devices, which integrates topics in many research disciplines-from materials science and chemistry to electronics and bioengineering-together.

Autonomous Underwater Self-Healable Adhesive Elastomers Enabled by Dynamical Hydrophobic Phase-Separated Microdomains

High-efficient underwater self-healing materials with reliable mechanical attributes hold great promise for applications in ocean explorations and diverse underwater operations. Nevertheless, achieving these functions in aquatic environments is challenging because the recombination of dynamic interactions will suffer from resistance to interfacial water molecules. Herein, an ultra-robust and all-environment stable self-healable polyurethane-amide supramolecular elastomer is developed through rational engineering of hydrophobic domains and multistrength hydrogen bonding interactions to provide mechanical and healing compatibility as well as efficient suppression of water ingress. The coupling of hydrophobic chains and hierarchical hydrogen bonds within a multiphase matrix self-assemble to generate dynamical hydrophobic hard-phase microdomains, which synergistically realize high stretchability (1601%), extreme toughness (87.1 MJ m-3), and outstanding capability to autonomous self-healing in various harsh aqueous conditions with an efficiency of 58% and healed strength of 12.7 MPa underwater. Furthermore, the self-aggregation of hydrophobic clusters with sufficient dynamic interactions endows the resultant elastomer with effective instantaneous adhesion (6.2 MPa, 941.9 N m-1) in extremely harsh aqueous conditions. It is revealed that the dynamical hydrophobic hard-phase microdomain composed of hydrophobic barriers and cooperative reversible interactions allows for regulating its mechanical enhancement and underwater self-healing efficiency, enabling the elastomers as intelligent sealing devices in marine applications.

Dynamic Covalent Bond-Based Polymer Chains Operating Reversibly with Temperature Changes

Dynamic bonds can facilitate reversible formation and dissociation of connections in response to external stimuli, endowing materials with shape memory and self-healing capabilities. Temperature is an external stimulus that can be easily controlled through heat. Dynamic covalent bonds in response to temperature can reversibly connect, exchange, and convert chains in the polymer. In this review, we introduce dynamic covalent bonds that operate without catalysts in various temperature ranges. The basic bonding mechanism and the kinetics are examined to understand dynamic covalent chemistry reversibly performed by equilibrium control. Furthermore, a recent synthesis method that implements dynamic covalent coupling based on various polymers is introduced. Dynamic covalent bonds that operate depending on temperature can be applied and expand the use of polymers, providing predictions for the development of future smart materials.

Ligand Dissociation of Metal-Complex Photocatalysts toward pH-Photomanipulation in Dynamic Covalent Hydrogels for Printing Reprocessable and Recyclable Devices

Dynamic covalent hydrogels are gaining attention for their potential in smart materials, soft devices, electronics, and more thanks to their impressive mechanical properties, biomimetic structures, and dynamic behavior. However, a significant challenge lies in designing precise and efficient dynamic photochemistry for their preparation, allowing for complex structures and control over the dynamic process. Herein, we propose a general and straightforward orthogonal dynamic covalent photochemistry strategy for preparing high-performance printable dynamic covalent hydrogels, thereby broadening their advanced applications. This photochemical strategy uses a bifunctional photocatalyst to initiate radical polymerization and release ligands through a rapid light-mediated dissociation mechanism. This process leads to a controlled increase in system pH from mildly acidic to alkaline conditions within one hundred seconds, which in turn triggers the pH-sensitive model reactions of boronic acid/diol complexation and Knoevenagel condensation. The orthogonal photochemistry enables the formation of interpenetrated and conjoined networks, significantly enhancing the mechanical properties of the hydrogels. The reversible bonds formed during the process, i.e., boronic ester and unsaturated ketone bonds, confer excellent self-healing, reprocessable, and recyclable properties on the hydrogels through photochemical pH variations. Furthermore, this rapid, controlled fabrication process and dynamic behavior are highly compatible with printing techniques, enabling the design of adaptive and recyclable sensors with different structures. These advancements are promising for various material science, medicine, and engineering applications.