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Self-powered information encoding devices (IEDs) have drawn considerable interest owing to their capability to process information without batteries. Next-generation IEDs should be reprogrammable, self-healing, and wearable to satisfy the emerging requirements for multifunctional IEDs; however, such devices have not been demonstrated. Herein, an integrated triboelectric nanogenerator-based IED with the aforementioned features was developed based on the designed light-responsive high-permittivity poly(sebacoyl diglyceride

Soft robotics locomotion at the liquid-air interface has become more and more important for an intelligent society. However, existing locomotion of soft robotics is limited to two dimensions. It remains a formidable challenge to realize three-dimensional locomotion (

Oxime-urethane bond featuring with high reversibility even at room temperature and multiple reactivity is an emerging dynamic covalent bond, and has shown great potential for self-healing polymers, which are one of the most attractive development directions for next generation of polymeric materials. In this review, recent progresses on the oxime-urethane-based self-healing polymers, including their designs and applications in diverse fields such as biomedicine, flexible electronics, soft robots, 3D printing, protective materials, and adhesives, are summarized, and outlooks on the future development of this field are discussed.

Conventional two-dimensional (2D) cell culture is dramatically different from three-dimensional (3D) in vivo environment cells experience in vivo. Here, a new kind of 3D cell culture with a biomimetic structure to natural extracellular matrix (ECM) based on bacterial cellulose (BC) nanofibers and poly(glycerol-sebacate) (PGS) was designed. The 3D PGS/BC cell culture shows a porous and nanofibrous structure which was formed through biosynthesis of nanofibers secreted by G. xylinus on the porous PGS. The mechanical properties of PGS were significantly enhanced by the incorporation of BC nanofibers, which improved sample handling for application. L929 mouse fibroblasts and HUVECs were used as model cells to evaluate the potential ability of PGS/BC as cell culture. The results show that 3D PGS/BC promotes cell growth by facilitating cell proliferation, cell morphology and exhibit comparable performance to commercial Alvetex® cell culture. The BC nanofibers reinforced PGS/BC cell culture provides a 3D biomimetic structure to ECM which is beneficial to cellular adhesion and interaction. It is believed that the degradable PGS/BC has great potential applications for cell culture or tissue engineering scaffold.

Ionogels with high transparency, stretchability and self-healing capability show great potential for wearable electronics. Here, a kind of highly transparent, stretchable and self-healable ionogels are designed using double physical cross-linking including hydrogen bonding and dipole–dipole interaction. Owing to the dynamic and reversible nature of the ion–dipole interaction and hydrogen bonds of polymeric chains, the ionogel possesses good self-healing capability. The multifunctional sensors for strain and temperature are fabricated based on ionogel. The ionogel can serve as strain sensor that exhibited high sensitivity [gauge factor (GF) = 3.06] and durability (1000 cycles) to a wide range of strains (0–300%). Meanwhile, the ionogel shows rapid response to temperature, due to the temperature dependence of its ionic conductivity. Furthermore, the ionogel fibers with excellent antifreezing (− 20 °C) capability are fabricated, and the fibers show the good sensing performance to human motions and temperature. Importantly, the antifreezing ionogel-based triboelectric nanogenerator (ITENG) is assembled for efficient energy harvesting. The ITENG shows a short circuit current (ISC) of 6.1 μA, open circuit voltage (VOC) of 115 V, and instantaneous peak power density of 334 mW m−2. This work provides a new strategy to design ionogels for the advancement of wearable electronics.

Covalent adaptable networks (CANs) are polymeric networks containing dynamic covalent bonds. Vinyl CANs are the high-performance counterparts of vinyl thermoplastics and show great potential for us...

Polyurethane hot-melt adhesives featured with high adhesion strength and environmental friendliness possess broad applications in many fields. However, their practical application is hindered by existing drawbacks such as low adhesion strength and poor recyclability for thermoplastic polyurethane and reactive polyurethane hot-melt adhesives, respectively. Achieving high adhesion strength and efficient recycling for hot-melt adhesives simultaneously is challenging. Herein, reversible covalent bonds (oxime–carbamate) were introduced to construct a three-dimensional dynamically cross-linked polyurethane system which has the merits of favorably reworkable thermoplastic polyurethane hot-melt adhesives and high adhesive reactive polyurethane hot-melt adhesives to accomplish efficient bonding–debonding conversion on demand. Such a structure provided a high cross-linked covalent network and a fast reversible adhesive property, and hence improved the overall performance of holt-melt adhesives. As a result, the adhesive exhibited an impressive initial and ultimate adhesion strength of 5.96 ± 0.61 MPa (5 min curing) and 9.02 ± 1.36 MPa (10 days curing), respectively. More remarkably, favorable repeated adhesive capability was realized even after it was completely broken four times, while still retaining all above 4.40 ± 0.92 MPa. In addition, this adhesive also possessed excellent solvent resistance and good durability. Our work emphasized the importance of molecular design and a general method for strong and efficient adhesive systems.

Vanadium nitride (VN)-based materials have been investigated as negative electrode materials for supercapacitors (SCs) owing to their high theoretical capacitances and suitable negative potential windows. However, viable VN-based negative electrode materials suffer from irreversible electrochemical oxidation of the soluble vanadium species, leading to rapid capacitance fading when operated in aqueous electrolytes. Developing a versatile approach to enhance the stability of VN in aqueous electrolytes is still a challenge. Here, an interface engineering strategy is developed to intentionally introduce surface nanolayers of vanadium oxides (VOX) as a reactive template on the VN surface to formulate well-designed polypyrrole@VNO (Ppy@VNO) core-shell nanowires (NWs) incorporated into a 3D porous N-doped graphene (NG) hybrid aerogel as a durable negative electrode for SCs. Experimental and theoretical investigations reveal that the in-situ constructed Ppy@VNO core-shell host can offer more efficient pathways for rapid electron/ion transport and accessible electroactive sites. Most importantly, a reversible surface redox reaction is realized through the transformation of the valence state of V, and a long cyclic stability is achieved. The Ppy@VNO/NG hybrid aerogel can deliver a high specific capacitance of 650 F g−1 at 1 A g−1 with approximately 70.7% capacitance retention (up to the twenty fold current density), and an excellent cycling stability without any capacitance de cay after 10,000 cycles at both low and high current densities (1 and 10 A g−1, respectively). This work paves the way for the development of advanced electrode materials for SCs.

Three-dimensional (3D) printing has had a large impact on various fields, with fused deposition modeling (FDM) being the most versatile and cost-effective 3D printing technology. However, FDM often requires sacrificial support structures, which significantly complicates the processing and increases the cost. Furthermore, poor layer-to-layer adhesion greatly affects the mechanical stability of 3D-printed objects. Here, we present a new Print-Healing strategy to address the aforementioned challenges. A polymer ink (Cu-DOU-CPU) with synergetic triple dynamic bonds was developed to have excellent printability and room-temperature self-healing ability. Objects with various shapes were printed using a simple compact 3D printer, and readily assembled into large sophisticated architectures via self-healing. Triple dynamic bonds induce strong binding between layers. Additionally, damaged printed objects can spontaneously heal, which significantly elongates their service life. This work paves a simple and powerful way to solve the key bottlenecks in FDM 3D printing, and will have diverse applications.

Peripheral nerve injury (PNI) caused by trauma, chronic disease and other factors may lead to partial or complete loss of sensory, motor and autonomic functions, as well as neuropathic pain. Biological activities are always accompanied by mechanical stimulation, and biomechanical microenvironmental homeostasis plays a complicated role in tissue repair and regeneration. Recent studies have focused on the effects of biomechanical microenvironment on peripheral nervous system development and function maintenance, as well as neural regrowth following PNI. For example, biomechanical factors-induced cluster gene expression changes contribute to formation of peripheral nerve structure and maintenance of physiological function. In addition, extracellular matrix and cell responses to biomechanical microenvironment alterations after PNI directly trigger a series of cascades for the well-organized peripheral nerve regeneration (PNR) process, where cell adhesion molecules, cytoskeletons and mechanically gated ion channels serve as mechanosensitive units, mechanical effector including focal adhesion kinase (FAK) and yes-associated protein (YAP)/transcriptional coactivator with PDZ-binding motif (TAZ) as mechanotransduction elements. With the rapid development of tissue engineering techniques, a substantial number of PNR strategies such as aligned nerve guidance conduits, three-dimensional topological designs and piezoelectric scaffolds emerge expected to improve the neural biomechanical microenvironment in case of PNI. These tissue engineering nerve grafts display optimized mechanical properties and outstanding mechanomodulatory effects, but a few bottlenecks restrict their application scenes. In this review, the current understanding in biomechanical microenvironment homeostasis associated with peripheral nerve function and PNR is integrated, where we proposed the importance of balances of mechanosensitive elements, cytoskeletal structures, mechanotransduction cascades, and extracellular matrix components; a wide variety of promising tissue engineering strategies based on biomechanical modulation are introduced with some suggestions and prospects for future directions.

Despite decades of research, spinal cord injury (SCI) still causes irreparable damage to the human body. Key challenges that hinder the regeneration and extension of neurons following SCI must be overcome, including the overexpressed glial scar formation and strong inflammatory responses in lesion tissue. Transplantation of neural stem cells (NSCs) represents a promising therapeutic method due to its beneficial roles like growth factor secretion and anti-inflammation. However, NSCs usually differentiate into astrocytes, which is considered as one potential limitation of current NSC therapy. Herein, we fabricate an elastic poly(sebacoyl diglyceride) (PSeD) scaffold to mimic the mechanical properties of the natural spinal cord. The PSeD scaffold is coated with poly(sebacoyl diglyceride)-isoleucine-lysine-valine-alanine-valine-serine (PSeD-IKVAVS) to create a bioactive interface. The core point of this topic is divided into two parts. First, PSeD is a bioelastomer and its mechanical properties are similar to those of the natural spinal cord. This feature reduces the direct stimulation to the spinal cord tissue by the elastomer and then reduces the immune response or resistance caused by the host spinal cord tissue. Second, the IKVAVS peptide modifies PSeD to create a bioactive interface to support NSC growth and differentiation. In the in vivo study, the number of CD68-positive macrophages decreased in the PSeD-IKVAVS/NSC group compared to that in the SCI group (20% vs 60%). The low inflammation induced by the scaffold was beneficial to NSCs, resulting in increased locomotor recovery, as indicated by the increased Basso-Beattie-Bresnahan score (5, the average score in the PSeD-IKVAVS/NSC group, vs 2, the average score in the SCI group). Based on the above two characteristics, a PSeD-IKVAVS bioelastomer is fabricated, which provides a beneficial and bioactive microenvironment for NSCs after transplantation.

Synergetically integrating multiple capabilities into a nanostructured material has become one kind of reliable and sustainable strategy for resolving tricky issues in the energy and environmental fields. Herein, we prepare a series of nanochannel thin films by simply assembling cellulose nanofibers with reduced graphene oxide, dominantly driven by van der Waals interactions. The thicknesses of the as-prepared thin films can be well controlled within several micrometers. Their highly compact nanochannel structures were evidenced by the densities of up to 1.1 g cm−3 and the largest Brunauer–Emmett–Teller specific area of 126 m2 g−1, endowing them with excellent hygroscopicities (282 mg g−1) and exceptional in-plane thermal conductivities (614–1238 W m−1 K−1 at 25–80 °C), among the highest values for carbon-based composites. Such thin-film composites are readily used for solar-steam generators, delivering an evaporation rate of 1.47 kg m−2 h−1 under 1 sun illumination, and are also easy to integrate into a high-performance amplified system for desalination on a large scale under natural solar irradiation.

Alveolar bone defects can arise as a consequence of trauma, infection, periodontal disease, or congenital alveolar fenestration. Many approaches have been employed in an effort to treat or overcome such defects, but the ability to effectively achieve alveolar regeneration remains elusive. Platelet-derived growth factor-BB (PDGF-BB) has been shown to serve as a key factor capable of orchestrating cell proliferation, angiogenesis, and chemoattraction in the context of osteogenic processes. Exactly how PDGF-BB affects human periodontal ligament stem cells (hPDLSCs), however, requires further exploration. In this report, we utilized a lentiviral construct to achieve PDGF-BB overexpression in hPDLSCs, allowing us to establish that this gene was able to enhance the proliferation of these cells and to mediate osteogenic gene upregulation therein. In addition, we established a rat model of alveolar defects that were implanted using different complexes, and then monitored through histological and micro-CT analyses 4 and 8 weeks postsurgery to assess bone repair outcomes. These analyses revealed that a thermosensitive hydrogel was an effective 3D cell culture scaffold, while PDLSCs overexpressing PDGF-BB enhanced bone growth in the context of alveolar bone defects. Together, these results thus indicate that PDGF-BB represents a potent means of promoting stem cell-based alveolar bone tissue regeneration.

Three-dimensional (3D)-printed scaffolds are widely used in tissue engineering to help regenerate critical-sized bone defects. However, conventional scaffolds possess relatively simple porous structures that limit the delivery of oxygen and nutrients to cells, leading to insufficient bone regeneration. Accordingly, in the present study, perfusable and permeable polycaprolactone scaffolds with highly interconnected hollow-pipe structures that mimic natural micro-vascular networks are prepared by an indirect one-pot 3D-printing method. In vitro experiments demonstrate that hollow-pipe-structured (HPS) scaffolds promote cell attachment, proliferation, osteogenesis and angiogenesis compared to the normal non-hollow-pipe-structured scaffolds. Furthermore, in vivo studies reveal that HPS scaffolds enhance bone regeneration and vascularization in rabbit bone defects, as observed at 8 and 12 weeks, respectively. Thus, the fabricated HPS scaffolds are promising candidates for the repair of critical-sized bone defects.

The unique properties of self-healing materials hold great potential in the field of biomedical engineering. Although previous studies have focused on the design and synthesis of self-healing materials, their application in in vivo settings remains limited. Here, we design a series of biodegradable and biocompatible self-healing elastomers (SHEs) with tunable mechanical properties, and apply them to various disease models in vivo, in order to test their reparative potential in multiple tissues and at physiological conditions. We validate the effectiveness of SHEs as promising therapies for aortic aneurysm, nerve coaptation and bone immobilization in three animal models. The data presented here support the translation potential of SHEs in diverse settings, and pave the way for the development of self-healing materials in clinical contexts., The unique properties of self-healing materials hold great potential in the field of biomedical engineering. Here, the authors designed a series of biodegradable and biocompatible self-healing elastomers with tunable mechanical properties, and apply them to various disease models in vivo, including aortic aneurism, bone fracture and nerve amputation.

For the surgical treatment of coronary artery disease, renal artery stenosis and other peripheral vascular diseases, there is significant demand for small diameter (inner diameter6 mm) vascular grafts. However, autologous grafts are not always available when the substitute vascular grafts are severely diseased. In our previous work, hybrid small-diameter vascular grafts were successfully fabricated by combining electrospun polycaprolactone (PCL) and decellularized rat aorta (DRA). However, histological assessments of these grafts revealed the development of intimal hyperplasia, indicating potential negative impacts on the long-term patency of these grafts. To address this challenge, PCL nanofibers blended with rapamycin (RM) were electrospun outside the decellularized vascular graft to fabricate a RM-loaded hybrid tissue-engineered vascular graft (RM-HTEV), endowing the graft with a drug delivery function to prevent intimal hyperplasia. RM-HTEV possessed superior mechanical properties compared to DRA and exhibited a sustained drug release profile. To evaluate the applicability of RM-HTEV in vivo, abdominal aorta transplantation was performed on rats. Doppler sonography showed that the grafts were functional for up to 8 weeks in vivo. Moreover, histological analysis of explanted grafts 12 weeks postimplantation demonstrated that RM-HTEV significantly decreased neo-intimal hyperplasia compared with HTEV, without impairing reendothelialization and M2 macrophage polarization. Overall, RM-HTEV represents a promising strategy for developing small-diameter vascular grafts with great clinical translational potential. STATEMENT OF SIGNIFICANCE: In this study, a new type of rapamycin-loaded hybrid tissue-engineered vascular graft (RM-HTEV) was fabricated using electrospinning technology. The unique hybrid bi-layer structure endowed the RM-HTEV with multi-functionality: the exterior rapamycin-loaded electrospun PCL nanofibrous layer enhanced the mechanical properties of the graft and possessed drug releasing property; the interior decellularized aorta layer with porous structure could facilitate cell proliferation and migration. In in vivo implantation experiment, RM-HTEV exhibited satisfying long-term patency rate and significantly inhibited intimal hyperplasia without impairing re-endothelialization and M2 macrophage polarization. This strategy is expected to be a promising strategy for developing bioactive small-diameter vascular grafts with great clinical translational potential.

Long-segment defects remain a major problem in clinical treatment of tubular tissue reconstruction. The design of tubular scaffold with desired structure and functional properties suitable for tubular tissue regeneration remains a great challenge in regenerative medicine. Here, we present a reliable method to rapidly fabricate tissue- engineered tubular scaffold with hierarchical structure via 4-axis printing system. The fabrication process can be adapted to various biomaterials including hydrogels, thermoplastic materials and thermosetting materials. Using polycaprolactone (PCL) as an example, we successfully fabricated the scaffolds with tunable tubular architecture, controllable mesh structure, radial elasticity, good flexibility, and luminal patency. As a preliminary demonstration of the applications of this technology, we prepared a hybrid tubular scaffold via the combination of the 4-axis printed elastic poly(glycerol sebacate) (PGS) bio-spring and electrospun gelatin nanofibers. The scaffolds seeded with chondrocytes formed tubular mature cartilage-like tissue both via in vitro culture and subcutaneous implantation in the nude mouse, which showed great potential for tracheal cartilage reconstruction.

There is an urgent clinical demand to develop a functional small diameter vascular graft with long-term patency, which mainly relies on the anticoagulation and endothelialization of the vascular graft. In addition, improved degradation of vascular graft provides more space for cell infiltration and facilitates remodeling of blood vessel. In this study, an elastic and biomimetic nanofibrous vascular scaffold with improved degradability was prepared by adding poly(lactic-co-glycolic acid) (PLGA) into the poly(L-lactic acid) (PLLA)/poly(L-lactide-co-ε-caprolactone) (PLCL) blend using thermally induced phase separation (TIPS) technique. The incorporation of PLGA also improved the hydrophilicity of the composite scaffold. Then the vascular scaffold was surface modified by combination of heparin and stromal cell-derived factor-1 alpha (SDF-1α). The results of whole blood clotting kinetics and plasma recalcification profiles indicated that heparinized modification significantly enhanced the anticoagulation of vascular scaffold. In vitro cell culture assays demonstrated the immobilized SDF-1α facilitated recruitment of endothelial progenitor cells (EPCs), migration and proliferation of mature endothelial cells, human umbilical vein endothelial cells (HUVECs), and expression of VE-cadherin/CD144 and endothelial nitric oxide synthase (eNOS) genes in HUVECs, thereby accelerating the endothelialization of the modified vascular scaffold. Besides, the nanofibrous vascular scaffold modified with heparin and SDF-1α inhibited the proliferation of human vascular smooth muscle cells (HVSMCs). Therefore, the phase separated nanofibrous vascular scaffold modified with heparin and SDF-1α shows the promising in vitro performance as a functional small diameter vascular graft.

Recently, a bilayered scaffold with an anisotropic structure mimicking a native osteochondral tissue shows considerable potential for treating osteochondral defects. Herein, a bilayered scaffold consisting of biomimetic cartilage and a subchondral bone architecture was constructed for repairing osteochondral defect. A hydrogel prepared by the Schiff base reaction of gelatin, silk fibroin, and oxidized dextran was designed as the cartilage layer, while a nanofibrous scaffold with a macroporous structure prepared from the polymer blend of poly(l-lactic acid)/poly(lactic-co-glycolic acid)/poly(e-caprolactone) using the dual phase separation technique served as a subchondral layer. The subchondral layer was then treated with polydopamine coating for osteogenic factor immobilization. To facilitate the chondrogenic and osteogenic differentiation of bone marrow mesenchymal stem cells on the bilayered scaffold, the cartilage-inducing drug kartogenin (KGN) and osteogenic-inducing factor bone morphogenetic protein 2-derived peptides (P24 peptides) were, respectively, loaded on the subchondral layer. Next, the in vitro release of KGN and P24 peptide from the corresponding layer was monitored, respectively, and the results showed that both the release time of KGN and P24 peptides would last for more than 28 days. The in vitro results indicated that the KGN-loaded cartilage layer and P24 peptides-loaded subchondral layer were capable of supporting cell proliferation, and induced the chondrogenic and osteogenic differentiation, respectively. Furthermore, the in vivo experiments suggested that the bilayered scaffold significantly accelerated the regeneration of the osteochondral tissue in the rabbit knee joint model. Consequently, this bilayered scaffold loaded with KGN and P24 peptides would be a promising candidate for repairing osteochondral defect.