In this study, the crystallization behavior of PA6/PA66 alloys was studied using in situ FTIR spectroscopy, combined with Proj-MW2D correlation analysis and DSC measurements. The method for ...calculating the generation enthalpy of hydrogen bonds during PA6/PA66 alloys crystallization was also established via Van't Hoff analysis. The essential reason for the crystallization reduction for both PA6 and PA66 in alloys was elucidated from the perspective of hydrogen bonds. Compared with neat PA6 and neat PA66, DSC measurements showed that the crystallization ability of both PA6 and PA66 in the alloys obviously decreased. From the results of the generation enthalpies of the hydrogen bonds, it was confirmed that the capability for hydrogen bond generation of both PA6 and PA66 in PA6/PA66 alloys was significantly reduced. The molecular chain motions of PA6 and PA66 during the alloy crystallization were successfully separated using Proj-MW2D correlation FTIR spectroscopy. Two main issues were addressed. The first one is that the generating capacity of hydrogen bonds between PA6 and PA66 is actually very weak, although this type of hydrogen bond can be generated in theory. The second is that non-hydrogen bonded molecular chains of PA66 are also involved in the PA6 crystallization, and the molecular chains of amorphous state PA66 hinder the generation of hydrogen bonds between PA6 molecular chains, resulting in a significant crystallization reduction of PA6 in PA6/PA66 alloys.
Water-rich conductive hydrogels with excellent stretchability are promising in strain sensors due to their potential application in flexible electronics. However, the features of being water-rich ...also limit their working environment. Hydrogels must be frozen at subzero temperatures and dried out under ambient conditions, leading to a loss of mechanical and electric properties. Herein, we prepare HAG
hydrogels (a polyacrylic acid (HAPAA) hydrogel in a binary water-glycerol solution, where x is the mass ratio of water to glycerol), in which the water is replaced with water-glycerol mixed solutions. The as-prepared HAG
hydrogels show great anti-freezing properties at a range of -70 to 25 °C, as well as excellent moisture stability (the weight retention rate was as high as 93% after 14 days). With the increase of glycerol, HAG
hydrogels demonstrate a superior stretchable and self-healing ability, which could even be stretched to more than 6000% without breaking, and had a 100% self-healing efficiency. The HAG
hydrogels had good self-healing ability at subzero temperatures. In addition, HAG
hydrogels also had eye-catching adhesive properties and transparency, which is helpful when used as strain sensors.
Antibiotic residues in the environment pose a serious threat to ecosystems and human health. Therefore, it is important to develop sensitive and rapid in situ detection methods. In this work, the ...designed nanozymes, with excellent four enzyme activities, were proved to be constituted of unique hollow nanocage structures (CoZnSe@CN HCs). Based on the peroxidase-like enzymes, a portable colorimetric sensor was constructed for the on-site determination of tetracycline (TC) in real samples. The linear range of TC detection was 0.1–100 μM, and the detection limit was 0.02 μM. At the same time, colorimetric detection and smartphones have also been combined for on-site colorimetric detection of TC. In-depth exploration of the detection mechanism showed that TC could be bound with the material, inhibiting the production of oxidized 3,3′,5,5′-tetramethylbenzidine. The sensor was also used for the detection of TC in environmental soil and water samples. This study can provide an intelligent detection method for environmental monitoring.
Graphical abstract
Excellent mechanical properties and self-healing properties are very important for the practical application of hydrogel flexible sensors. In this study, acrylic acid and stearyl methyl acrylate were ...selected as monomers to synthesize hydrophobic association hydrogels, and multi-physically cross-linked hydrogels were synthesized by adding ferric chloride and polyvinyl alcohol to introduce ion interaction and a hydrogen bond cross-linking network. The hydrogels were characterized by FTIR, XRD and SEM, and the mechanical properties and self-healing properties were tested using a universal testing machine. It was confirmed that the strength of the hydrogel was significantly improved with the addition of ferric chloride and polyvinyl alcohol, and the hydrogel still showed good self-healing properties. Further testing of its application as a conductive sensor has demonstrated sensitive and stable motion sensing capabilities. This provides an important reference for high-performance hydrogel sensors with both high strength and self-healing properties.
It is a challenge to manufacture flexible sensors that possess easily distinguishable biomotion signals, strong response reliability, and excellent self‐healing capability. Herein, a self‐healing ...sensor with tunable positive/negative piezoresistivity is designed by the construction of hierarchical structure connected through supramolecular metal–ligand coordination bonds. The developed sensors can be integrated with the human body to detect multiple tiny signals, such as pronunciation, coughing, and deep breathing. Interestingly, the nanostructured elastomer sensor with and without a flexible yarn electrode shows negative and positive current signals, respectively, making it easy to be identify. Furthermore, it exhibits very fast (2 min), autonomous, and repeatable self‐healing ability with high‐healing efficiency (88.6% after the third healing process). The healed samples still possess flexibility, high sensitivity, and accurate detection capability, even after bending over 10 000 cycles. The excellent biomimetic self‐healing performance combined with the tunable piezoresistivity make it promising for next‐generation wearable electronics.
Self‐healing sensors with tunable positive/negative piezoresistivity are developed by the construction of hierarchical structure connected through supramolecular metal–ligand coordination bonds. The resultant strain sensor exhibits very fast, autonomous, and repeatable self‐healing ability with high‐healing efficiency. More interestingly, it presents tunable positive/negative piezoresistivity, making it easy to be identified and is highly desired for human–machine interface application.
Despite the tremendous advancement of intelligent robots, it remains a great challenge to integrate living organisms‐like multistimuli responsive actuation and excellent self‐healing ability into one ...single material system, which will greatly benefit and broaden the development of smart biomimetic materials. Herein, a novel self‐healable multistimuli responsive actuator is developed based on hierarchical structural design and interfacial supramolecular crosslinking. The resulting biomimetic actuator shows a record high photothermal efficiency (ηPT = 79.1%) and thermal conductivity (31.92 W m−1 K−1), and presents a superfast actuating response (near‐infrared light: 0.44 s; magnetic field: 0.36 s). In addition, the supramolecular crosslinking endows excellent self‐healing performance in both mechanical and actuating properties to the material. This biomimetic actuator with its hierarchical structure design provides great potential for various applications, such as artificial muscles, soft robotics, and biomedical microdevices.
Self‐healing actuators with a superfast light‐ and magnetic‐response are developed based on hierarchical structural design and interfacial supramolecular crosslinking. The resultant actuator exhibits an unprecedented high photothermal conversion efficiency and heat transfer rate, as well as superfast near‐infrared‐ and magnetic‐responsive sensitivity and repeatability. Meanwhile, it features desirable self‐healing efficiency even in harsh conditions, allowing for long‐term stable operation.
Soft materials that can reversibly transform shape in response to moisture have applications in diverse areas such as soft robotics and biomedicine. However, the design of a structurally ...transformable or mechanically self‐healing version of such a humidity‐responsive material, which can arbitrarily change shape and reconfigure its 3D structures remains challenging. Here, by drawing inspiration from a covalent–noncovalent network, an elaborately designed biopolyester is developed that features a simple hygroscopic actuation mechanism, straightforward manufacturability at low ambient temperature (≤35 °C), fast and stable response, robust mechanical properties, and excellent self‐healing ability. Diverse functions derived from various 3D shapes that can grasp, swing, close–open, lift, or transport an object are further demonstrated. This strategy of easy‐to‐process 3D structured self‐healing actuators is expected to combine with other actuation mechanisms to extend new possibilities in diverse practical applications.
An elaborately designed hygroscopic actuator is synthesized with hydrogen bonding and a covalently bonded interpenetrating network. It features straightforward shaping processability at low ambient temperature (≤35 °C), fast and stable response, robust mechanical properties, and excellent self‐healing ability. Therefore, diverse functions derived from various 3D shapes are demonstrated, including grasping, swinging, closing–opening, lifting, or transporting an object.
Conductive self-healing hydrogels (CSHs) that match the mechanical properties of biological tissues are highly desired for emerging wearable electronics. However, it is still a fundamental challenge ...to balance the trade-offs among the mechanical, electronic, and self-healing properties in CSHs. In this study, we presented supramolecular double-network (DN) CSHs by pre-infiltrating conductive polyaniline (PANI) precursor into the self-healable hydrophobic association poly(acrylic acid) (HAPAA) hydrogel matrix. The dynamic interfacial interactions between the HAPAA and PANI networks efficiently enhanced the mechanical performances of the HAPAA/PANI (PAAN) hydrogel and could compensate for the negative effect of the enhanced mechanical strength on self-healing. In addition, the interconnected PANI network endowed the PAAN hydrogel with high conductivity and excellent sensory performances. As such, the mechanical and electronic properties of the PAAN hydrogel were simultaneously enhanced significantly without compromising the self-healing performance of the HAPAA matrix, achieving balanced mechanical, electronic, and self-healing properties in the PAAN hydrogel. Lastly, proof-of-concept applications like human physiological monitoring electronics, flexible touch screens, and artificial electronic skin are successfully demonstrated using the PAAN hydrogel with the capability of restoring their electronic performances after the healing process. It is anticipated that such hydrogel network design can be extended into next-generation hydrogel electronics for human-machine-interfaces and soft robotics.
Highly efficient and mechanically durable photothermal materials are urgently needed for solar harvesting, but their development still remains challenging. Here, inspired by the hierarchically ...oriented architecture of natural spider silk, an ultrarobust liquid metals (LMs)/polymer composite is presented via dynamic crosslinking based on the unique mechanical deformable characteristic of LMs. Dynamically cross‐linked core–shell structured LMs droplets can be squeezed along with the orientational crystallization of polymer chains during drawing, thus enabling LMs nanoparticles to be uniformly programmed in the rigid polyethylene nanofiber skeleton. The resultant composite exhibits an unprecedented combination of strong broad‐band light absorption (96.9–99.3%), excellent photothermal conversion ability, remarkable mechanical property (tensile strength of 283.7 MPa, which can lift 200 000 times its own weight), and long‐term structural reliability (bearing 100 000 bending cycles). A powerful and durable solar thermoelectric generator system for real‐environmental solar‐heat‐electricity conversion is further demonstrated, providing a valuable guidance for the design and fabrication of high‐performance solar‐harvesting materials.
An ultrarobust photothermal material with bionic orderly hierarchical architecture is designed via dynamic crosslinking based on the unique mechanical deformable characteristic of liquid metals. The proposed material exhibits an unprecedented combination of strong broad‐band light absorption, excellent photothermal conversion ability, remarkable mechanical property, and long‐term structural reliability.
This study fabricated a sensitive and fast response nano zinc oxide (nano-ZnO) ultraviolet (UV) photodetector on flexible polymer substrate via laser direct structuring (LDS) technology. The ...polystyrene-block-poly-(ethylene-co-propylene)-block-polystyrene copolymer/polypropylene (SEPS/PP) composites incorporated with laser sensitizer of copper hydroxyl phosphate Cu2(OH)PO4 were designed as flexible LDS material. X-ray photoelectron spectroscopy analysis confirmed that partial Cu2+ in SEPS/PP composites was reduced to Cu0 (element copper), which could be used as a catalyst for selective metallization. As a result, the well-defined interdigitated copper electrode was successfully fabricated on polymer substrate. Moreover, the UV photodetector was fabricated through spin-coating nano-ZnO on the interdigitated copper electrode. Photocurrent analysis demonstrated that the obtained UV photodetector exhibited excellent sensitivity and stability. The rise and decay times of the UV photodetector were less than 1 and 0.25 s, respectively. This study provided a guideline to develop electronic devices on flexible polymer materials based on LDS technology.
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