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Implanted biomaterials and devices face compromised functionality and efficacy in the long term owing to foreign body reactions and subsequent formation of fibrous capsules at the implant–tissue interfaces1–4. Here we demonstrate that an adhesive implant–tissue interface can mitigate fibrous capsule formation in diverse animal models, including rats, mice, humanized mice and pigs, by reducing the level of infiltration of inflammatory cells into the adhesive implant–tissue interface compared to the non-adhesive implant–tissue interface. Histological analysis shows that the adhesive implant–tissue interface does not form observable fibrous capsules on diverse organs, including the abdominal wall, colon, stomach, lung and heart, over 12 weeks in vivo. In vitro protein adsorption, multiplex Luminex assays, quantitative PCR, immunofluorescence analysis and RNA sequencing are additionally carried out to validate the hypothesis. We further demonstrate long-term bidirectional electrical communication enabled by implantable electrodes with an adhesive interface over 12 weeks in a rat model in vivo. These findings may offer a promising strategy for long-term anti-fibrotic implant–tissue interfaces.

The integrative regeneration of both articular cartilage and subchondral bone remains an unmet clinical need due to the difficulties of mimicking spatial complexity in native osteochondral tissues for artificial implants. Layer-by-layer fabrication strategies, such as 3D printing, have emerged as a promising technology replicating the stratified zonal architecture and varying microstructures and mechanical properties. However, the dynamic and circulating physiological environments, such as mass transportation or cell migration, usually distort the pre-confined biological properties in the layered implants, leading to undistinguished spatial variations and subsequently inefficient regenerations. This study introduced a biomimetic calcified interfacial layer into the scaffold as a compact barrier between a cartilage layer and a subchondral bone layer to facilitate osteogenic–chondrogenic repair. The calcified interfacial layer consisting of compact polycaprolactone (PCL), nano-hydroxyapatite, and tasquinimod (TA) can physically and biologically separate the cartilage layer (TA-mixed, chondrocytes-load gelatin methacrylate) from the subchondral bond layer (porous PCL). This introduction preserved the as-designed independent biological environment in each layer for both cartilage and bone regeneration, successfully inhibiting vascular invasion into the cartilage layer and preventing hyaluronic cartilage calcification owing to devascularization of TA. The improved integrative regeneration of cartilage and subchondral bone was validated through gross examination, micro-computed tomography (micro-CT), and histological and immunohistochemical analyses based on an in vivorat model. Moreover, gene and protein expression studies identified a key role of Caveolin (CAV-1) in promoting angiogenesis through the Wnt/β-catenin pathway and indicated that TA in the calcified layer blocked angiogenesis by inhibiting CAV-1.

Current clinically used electronic implants, including cardiac pacing leads for epicardial monitoring and stimulation of the heart, rely on surgical suturing or direct insertion of electrodes to the heart tissue. These approaches can cause tissue trauma during the implantation and retrieval of the pacing leads, with the potential for bleeding, tissue damage, and device failure. Here, we report a bioadhesive pacing lead that can directly interface with cardiac tissue through physical and covalent interactions to support minimally invasive adhesive implantation and gentle on-demand removal of the device with a detachment solution. We developed 3D-printable bioadhesive materials for customized fabrication of the device by graft-polymerizing polyacrylic acid on hydrophilic polyurethane and mixing with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) to obtain electrical conductivity. The bioadhesive construct exhibited mechanical properties similar to cardiac tissue and strong tissue adhesion, supporting stable electrical interfacing. Infusion of a detachment solution to cleave physical and covalent cross-links between the adhesive interface and the tissue allowed retrieval of the bioadhesive pacing leads in rat and porcine models without apparent tissue damage. Continuous and reliable cardiac monitoring and pacing of rodent and porcine hearts were demonstrated for 2 weeks with consistent capture threshold and sensing amplitude, in contrast to a commercially available alternative. Pacing and continuous telemetric monitoring were achieved in a porcine model. These findings may offer a promising platform for adhesive bioelectronic devices for cardiac monitoring and treatment.

Reliable functions of bioelectronic devices require conformal, stable and conductive interfaces with biological tissues. Integrating bioelectronic devices with tissues usually relies on physical attachment or surgical suturing; however, these methods face challenges such as non-conformal contact, unstable fixation, tissue damage, and/or scar formation. Here, we report an electrical bioadhesive (e-bioadhesive) interface, based on a thin layer of a graphene nanocomposite, that can provide rapid (adhesion formation within 5?s), robust (interfacial toughness >400?J?m-2) and on-demand detachable integration of bioelectronic devices on diverse wet dynamic tissues. The electrical conductivity (>2.6?S?m-1) of the e-bioadhesive interface further allows bidirectional bioelectronic communications. We demonstrate biocompatibility, applicability, mechanical and electrical stability, and recording and stimulation functionalities of the e-bioadhesive interface based on ex vivo porcine and in vivo rat models. These findings offer a promising strategy to improve tissue–device integration and enhance the performance of biointegrated electronic devices.

The determination of structural evolution at the atomic level is essential to understanding the intrinsic physics and chemistries of nanomaterials. Mechanochemistry represents a promising method to trace structural evolution, but conventional mechanical tension generates random breaking points, which makes it unavailable for effective analysis. It remains difficult to find an appropriate model to study shear deformations. Here, we synthesize high-modulus carbon nanotubes that can be cut precisely, and the structural evolution is efficiently investigated through a combination of geometry phase analysis and first-principles calculations. The lattice fluctuation depends on the anisotropy, chirality, curvature, and slicing rate. The strain distribution further reveals a plastic breaking mechanism for the conjugated carbon atoms under cutting. The resulting sliced carbon nanotubes with controllable sizes and open ends are promising for various applications, for example, as an anode material for lithium-ion batteries.

Mechanically responsive materials that are able to sense and respond to external stimuli have important applications in soft robotics and the formation of artificial muscles, such as intelligent electronics, prosthetic limbs, comfort-adjusting textiles and miniature actuators for microfluidics. However, previous artificial muscles based on polymer materials are insufficient in generating large actuations, fast responses, diverse deformation modes and high cycle performances. To this end, carbon nanotubes (CNTs) are proposed as promising candidates to be assembled into artificial muscles, as they are lightweight, robust and have high surface-to-volume ratios. This protocol describes a reproducible biomimetic method for preparing a family of hierarchically arranged helical fiber (HHF) actuators that are responsive to solvents and vapors. These HHFs are produced through helical assembly of CNTs into primary fibers and further twisting of the multi-ply primary fibers into a helical structure. A large number of nanoscale gaps between the CNTs and micron-scale gaps between the primary fibers ensure large volume changes and fast responses upon the infiltration of solvents and vapors (e.g., water, ethanol, acetone and dichloromethane) by capillarity. The modes of shape transformations can be modulated precisely by controlling how the CNTs are assembled into primary fibers, multi-ply primary fibers, HHFs and hierarchical springs. This protocol provides a prototype for preparing actuators with different fiber components. The overall time required for the preparation of HHF actuators is 17 h.

A novel fiber-shaped supercapacitor is created with high volumetric energy density by designing an asymmetric configuration and integrating multiple functional components for electrodes. More specifically, a ternary hybrid fiber is prepared as a positive electrode by growing MnO2nanosheets onto a conducting polymer-coated carbon nanotube fiber; an ordered microporous carbon/carbon nanotube hybrid fiber is made as a negative electrode; and the hybrid positive and negative fibers are assembled into a fiber-shaped asymmetric supercapacitor. It shows a high operating voltage of 1.8 V, compared with 0.8–1.0 V of their conventional counterparts based on aqueous gel electrolytes; in particular, it produces an energy density as high as 11.3 mWh/cm3which is on par with the thin-film lithium-ion batteries. It also exhibits remarkable cyclic stability and good rate performance. Due to the unique fiber shape, it can be woven or knitted into flexible power textiles.

Mechanical responsiveness in many plants is produced by helical organizations of cellulose microfibrils. However, simple mimicry of these naturally occurring helical structures does not produce artificial materials with the desired tunable actuations. Here, we show that actuating fibres that respond to solvent and vapour stimuli can be created through the hierarchical and helical assembly of aligned carbon nanotubes. Primary fibres consisting of helical assemblies of multiwalled carbon nanotubes are twisted together to form the helical actuating fibres. The nanoscale gaps between the nanotubes and micrometre-scale gaps among the primary fibres contribute to the rapid response and large actuation stroke of the actuating fibres. The compact coils allow the actuating fibre to rotate reversibly. We show that these fibres, which are lightweight, flexible and strong, are suitable for a variety of applications such as energy-harvesting generators, deformable sensing springs and smart textiles.

Carbon nanotubes (CNT), core–sheath CNT/reduced graphene oxide nanoribbon (RGONR), CNT/RGO composite, and RGO fibers have been compared as counter electrodes to fabricate novel dye-sensitized solar cells. For the I–/I3–electrolyte, the core–sheath CNT/RGONR fiber shows the best catalytic activity, which in turn produces the highest energy conversion efficiency of 5.64%. In contrast, for the organic T–/T2electrolyte, the highest energy conversion efficiency has been produced from the CNT fiber counter electrode with the maximal value of 4.78%. The different electrocatalytic activities among these four carbon nanostructured fibers on the two typical electrolytes of I–/I3–and T–/T2have been carefully investigated in this work.