State Key Laboratory of High Performance Complex Manufacturing

Bone biomaterials play a vital role in bone repair by providing the necessary substrate for cell adhesion, proliferation, and differentiation and by modulating cell activity and function. In past decades, extensive efforts have been devoted to developing bone biomaterials with a focus on the following issues: (1) developing ideal biomaterials with a combination of suitable biological and mechanical properties; (2) constructing a cell microenvironment with pores ranging in size from nanoscale to submicro- and microscale; and (3) inducing the oriented differentiation of stem cells for artificial-to-biological transformation. Here we present a comprehensive review of the state of the art of bone biomaterials and their interactions with stem cells. Typical bone biomaterials that have been developed, including bioactive ceramics, biodegradable polymers, and biodegradable metals, are reviewed, with an emphasis on their characteristics and applications. The necessary porous structure of bone biomaterials for the cell microenvironment is discussed, along with the corresponding fabrication methods. Additionally, the promising seed stem cells for bone repair are summarized, and their interaction mechanisms with bone biomaterials are discussed in detail. Special attention has been paid to the signaling pathways involved in the focal adhesion and osteogenic differentiation of stem cells on bone biomaterials. Finally, achievements regarding bone biomaterials are summarized, and future research directions are proposed.

The effective dissipation of heat is critical to the performance and longevity of high-power electronics, so it is important to prepare highly thermally conductive polymer-based packaging materials for efficient thermal management. Due to the excellent thermal conductivity of boron nitride nanosheets (BNNSs), the hexagonal boron nitride (hBN) powder was dissolved in a mixed solution of isopropanol and deionized water for ultrasonic exfoliation to obtain hydroxylated BN nanosheets. Then, the prepared BNNS was functionalized with (3-aminopropyl)triethoxysilane (APTES) to enhance its dispersibility and interfacial compatibility in the epoxy resin, which play an important role in the improvement of the thermal conductivity of the composites. Finally, APTES-BNNS was uniformly dispersed in the epoxy resin by solvent mixing, and the oriented APTES-BNNS/epoxy composites were prepared through spin-coating and hot-pressing methods. It was found that APTES-BNNS/epoxy composites prepared herein exhibited significant anisotropic thermal conductivity. The results show that the thermal conductivity of APTES-BNNS/epoxy composites reached 5.86 W/mK at a filler content of 40 wt % and these composites have favorable thermal stability and mechanical properties. The APTES-BNNS/epoxy composite prepared in this paper has excellent thermal management capability and can be applied to the packaging of high-power electronic devices.

The incorporation of hydroxyapatite (HAP) into poly-l-lactic acid (PLLA) matrix serving as bone scaffold is expected to exhibit bioactivity and osteoconductivity to those of the living bone. While too low degradation rate of HAP/PLLA scaffold hinders the activity because the embedded HAP in the PLLA matrix is difficult to contact and exchange ions with body fluid. In this study, biodegradable polymer poly (glycolic acid) (PGA) was blended into the HAP/PLLA scaffold fabricated by laser 3D printing to accelerate the degradation. The results indicated that the incorporation of PGA enhanced the degradation rate of scaffold as indicated by the weight loss increasing from 3.3% to 25.0% after immersion for 28 days, owing to the degradation of high hydrophilic PGA and the subsequent accelerated hydrolysis of PLLA chains. Moreover, a lot of pores produced by the degradation of the scaffold promoted the exposure of HAP from the matrix, which not only activated the deposition of bone like apatite on scaffold but also accelerated apatite growth. Cytocompatibility tests exhibited a good osteoblast adhesion, spreading and proliferation, suggesting the scaffold provided a suitable environment for cell cultivation. Furthermore, the scaffold displayed excellent bone defect repair capacity with the formation of abundant new bone tissue and blood vessel tissue, and both ends of defect region were bridged after 8 weeks of implantation.

Polyetheretherketone (PEEK)/β-tricalcium phosphate (β-TCP) scaffolds are expected to be able to combine the excellent mechanical strength of PEEK and the good bioactivity and biodegradability of β-TCP. While PEEK acts as a closed membrane in which β-TCP is completely wrapped after the melting/solidifying processing, the PEEK membrane degrades very little, hence the scaffolds cannot display bioactivity and biodegradability. The strategy reported here is to blend a biodegradable polymer with PEEK and β-TCP to fabricate multi-material scaffolds via selective laser sintering (SLS). The biodegradable polymer first degrades and leaves caverns on the closed membrane, and then the wrapped β-TCP is exposed to body fluid. In this study, poly(l-lactide) (PLLA) is adopted as the biodegradable polymer. The results show that large numbers of caverns form on the membrane with the degradation of PLLA, enabling direct contact between β-TCP and body fluid, and allowing for their ion-exchange. As a consequence, the scaffolds display the bioactivity, biodegradability and cytocompatibility. Moreover, bone defect repair studies reveal that new bone tissues grow from the margin towards the center of the scaffolds from the histological analysis. The bone defect region is completely connected to the host bone end after 8 weeks of implantation.

This review summarizes the current research status on biodegradable metals as bone implants, including their biodegradability, mechanical properties, and biocompatibility.

Abstract It is an urgent need that defect repair can develop from simple device fixation to living tissue reconstruction, from short life function replacement to permanent regeneration repair. At present, bone transplantation has become the second largest transplantation surgery after blood transfusion, and artificial bone transplantation generates great hope for the repair and treatment of bone defect. In order to repair bone defect, artificial bone must have good biological properties and sufficient mechanical properties, and it should also have the shape matching to bone defect site and the connected porous structure. For structures and properties requirements of artificial bone, in this review three major challenges faced by artificial bone transplantation are systemtically analyzed and current methods and strategies to address these issues are discussed: 1) the need for developing a type of bone scaffold material with both biological and mechanical properties, 2) the need for realizing the controllable fabrication of individual shape and multistage pore structure of bone scaffold, 3) the need for realizing the transformation from man‐made structure to biological structure. Besides, it summarizes the advantages and disadvantages of these methods and discusses the potential future directions of structural and functional adaptive artificial bone for bone defect regeneration.

The manipulation of crystal orientation from the thermodynamic equilibrium states is desired in layered hybrid perovskite films to direct charge transport and enhance the perovskite devices performance. Here we report a templated growth mechanism of layered perovskites from 3D-like perovskites which can be a general design rule to align layered perovskites along the out-of-plane direction in films made by both spin-coating and scalable blading process. The method involves suppressing the nucleation of both layered and 3D perovskites inside the perovskite solution using additional ammonium halide salts, which forces the film formation starts from solution surface. The fast drying of solvent at liquid surface leaves 3D-like perovskites which surprisingly templates the growth of layered perovskites, enabled by the periodic corner-sharing octahedra networks on the surface of 3D-like perovskites. This discovery provides deep insights into the nucleation behavior of octahedra-array-based perovskite materials, representing a general strategy to manipulate the orientation of layered perovskites.

Poly (lactic acid) (PLA) with good biodegradability, biocompatibility and processability has a wide application prospect in bone tissue engineering. However, PLA exhibits a very slow degradation rate, hindering the regeneration of new bone. In this study, the degradation mechanisms of PLA bone scaffold, including autocatalysis and non-catalysis, end-chain and random chain breaking, surface degradation and bulk degradation, were analyzed systematically, and the influence factors including crystallinity, molecular weight, pH, and so on, were introduced. On this basis, the strategies including blending, copolymerization, compounding and surface modification to accelerate the degradation of PLA were summarized, and the accelerating mechanisms were analyzed and discussed detailedly. In addition, rapid prototyping technologies with unique advantages on the structure and shape of scaffold were introduced. The mechanical properties (strength and modulus) and biological properties (in vivo and in vitro) of PLA scaffold were reviewed and discussed. Finally, the present problem of research including the simultaneous improvement of mechanical and degradation properties was put forward, and four-dimensional printing (4D printing) as an advanced technique which might bring new ideas to improve and extend the properties of PLA scaffold was mentioned.

Introduction: It is urgently needed to develop composite bone scaffold with excellent mechanical properties and bioactivity in bone tissue engineering. Combining graphene oxide (GO) and hydroxyapatite (HAP) for the reinforcement of biopolymer bone scaffold has emerged as a promising strategy. However, the dispersion of GO and HAP remains to be a big challenge. Objectives: In this present work, the mechanical properties of GO and the bioactivity of and HAP were combined respectively via in situ synthesis for reinforcing biopolymer bone scaffold. Methods: via electrovalent bonding to form homogeneously dispersed HAP nanorods. Thereby, the GO-HAP nanocomposite was blended with biopolymer poly-L-lactic acid (PLLA) for fabricating biopolymer scaffold by selective laser sintering (SLS). Results: GO nanosheets were uniformly decorated with HAP nanorods, which were about 60 nm in length and 5 nm in diameter. The compressive strength and modulus of PLLA/12%GO-HAP were significantly increased by 53.71% and 98.80% compared to the pure PLLA scaffold, respectively, explained on the base of pull out, crack bridging, deflection and pinning mechanisms. Meanwhile, the mineralization experiments indicated the PLLA/GO-HAP scaffold displayed good bioactivity by inducing the formation of apatite layer. Besides, cell culturing experiments demonstrated the favorable cytocompatibility of scaffold by promoting cell adhesion and proliferation. Conclusions: The present findings show the potential of PLLA/GO-HAP composite scaffold via in situ synthesis in bone tissue engineering.

Thermoelectric generators (TEGs) provide a unique solution for energy harvesting from waste heat, presenting a potential solution for green energy. However, traditional rigid and flexible TEGs cannot work on complex and dynamic surfaces. Here, we report a stretchable TEG (S-TEG) (over 50% stretchability of the entire device) that is geometrically suitable for various complex and dynamic surfaces of heat sources. The S-TEG consists of hot-pressed nanolayered p-(Sb2Te3) and n-(Bi2Te3)-type thermoelectric couple arrays and exploits the wavy serpentine interconnects to integrate all units. The internal resistance of a 10 × 10 array is 22 ohm, and the output power is ∼0.15 mW/cm2 at ΔT = 19 K on both developable and nondevelopable surfaces, which are much improved compared with those of existing S-TEGs. The energy harvesting of S-TEG from the dynamic surfaces of the human skin offers a potential energy solution for the wearable devices for health monitoring.

In this article, a just-in-time-learning (JITL)-aided canonical correlation analysis (CCA) is proposed for the monitoring and fault detection of multimode processes. A canonical correlation analysis (CCA)-based fault detection method has been applied to single-operating-mode processes. However, CCA has limitations in handling processes with multiple operating points. These limitations are illustrated by a numerical example. To reduce the time for searching relevant data, K-means is integrated into the JITL to build the local CCA model. Furthermore, the proposed method is compared with commonly used kernel-based methods in terms of computational complexity and interpretability of the results. Finally, the validity and efficacy of the proposed method are shown using an industrial benchmark process. Results show that the proposed method has better performance than conventional methods in terms of fault detection rate while still tracking changes in the system.

In present study, a strategy is presented to construct a magnetic micro-environment in poly-l-lactide/polyglycolic acid (PLLA/PGA) scaffolds fabricated via selective laser sintering by incorporating Fe3O4 magnetic nanoparticles (MNPs), aiming to enhance cell viability and promote bone regeneration. In the micro-environment, each nanoparticle provides a nanoscale magnetic field to activate cellular responses. The results in vitro demonstrated that the magnetic scaffolds not only stimulated cell adhesion and viability, but also enhanced proliferation rate and alkaline phosphatase activity. Meanwhile, the compressive strength and modulus were increased by 81.9% and 71.6%, respectively, which were determined by the rigid enhancement effect of MNPs. Moreover, the magnetic scaffolds were implanted into rabbit radius bone defect in vivo, and the results indicated that the magnetic scaffolds significantly induced substantial blood vessel tissue, fibrous tissue and new bone tissue formation at 2 months post-implantation, revealing the excellent bone regeneration capability. These positive results indicate that the construction of magnetic micro-environment in scaffolds is a working countermeasure to promote bone regeneration.

Additive manufacturing (AM), which is based on the principle of layer-by-layer shaping and stacking of discrete materials, has shown significant benefits in the fabrication of complicated implants for tissue engineering (TE). However, many native tissues exhibit anisotropic heterogenous constructs with diverse components and functions. Consequently, the replication of complicated biomimetic constructs using conventional AM processes based on a single material is challenging. Multimaterial 3D and 4D bioprinting (with time as the fourth dimension) has emerged as a promising solution for constructing multifunctional implants with heterogenous constructs that can mimic the host microenvironment better than single-material alternatives. Notably, 4D-printed multimaterial implants with biomimetic heterogenous architectures can provide a time-dependent programmable dynamic microenvironment that can promote cell activity and tissue regeneration in response to external stimuli. This paper first presents the typical design strategies of biomimetic heterogenous constructs in TE applications. Subsequently, the latest processes in the multimaterial 3D and 4D bioprinting of heterogenous tissue constructs are discussed, along with their advantages and challenges. In particular, the potential of multimaterial 4D bioprinting of smart multifunctional tissue constructs is highlighted. Furthermore, this review provides insights into how multimaterial 3D and 4D bioprinting can facilitate the realization of next-generation TE applications.

In this paper, two kinds of bi-layered chiral metamaterials were proposed to enhance the asymmetric transmission effects for circular polarized electromagnetic waves which are only found in planar chiral metamaterials according to previous studies. It was found that the magnitude of the asymmetric transmission parameters mainly depends on the distances between the two metal layers. With appropriate distance, the asymmetric transmission parameter for circular polarized electromagnetic waves can increase to 0.6. Moreover, both proposed configurations show no asymmetric transmission for linear polarized electromagnetic waves which is widely studied in other bi-layered metamaterials.

Magnetostrictive alloys have attracted increasing attention in biomedical applications because of the ability to generate reversible deformation in the presence of external magnetic fields. This review focuses on the advances in magnetostrictive alloys and their biomedical applications. The theories of magnetostriction are systematically summarized. The different types of magnetostrictive alloys and their preparation methods are also reviewed in detail. The magnetostrictive strains and phase compositions of typical magnetostrictive alloys, including iron based, rare-earth based and ferrite materials, are presented. Besides, a variety of approaches to preparing rods, blocks and films of magnetostriction materials, as well as the corresponding methods and setups for magnetostriction measurement, are summarized and discussed. Moreover, the interactions between magnetostrictive alloys and cells are analyzed and emphasis is placed on the transduction and transformation process of mechanochemical signals induced by magnetostriction. The latest applications of magnetostrictive alloys in remote microactuators, magnetic field sensors, wireless implantable devices and biodegradable implants are also reviewed. Furthermore, future research directions of magnetostrictive alloys are prospected with focus on their potential applications in remote cell actuation and bone repair.

This paper presents a general solution of precise position synchronous control for multi-axis servo systems. The control strategy to achieve high-precision motion is summarized in two main points: an adaptive-fuzzy friction compensator is adopted in the independent control loop of each axis to compensate the nonlinear friction, and then a method which combines global sliding mode control with two adjacent axes cross-coupling technology is proposed to minimize not only single-axis position error but also synchronous errors of all motion axes. At first, the adaptive fuzzy algorithm including dynamic model of the system is utilized to design a friction compensation controller. Next, to improve robustness of the multi-axis motion system against variation of motor parameters and external disturbances, global sliding mode control is introduced. In addition, the multi-axis synchronous control based on cross-coupling technology is elaborately designed via proportional-differential control law. The performance of the proposed control system is investigated through extensive simulations based on a popular motion platform. Furthermore, experimental study shows that the results successfully demonstrate the effectiveness of the proposed position synchronous control method for a general four-axis servo system.

An automatic system based on thermoelectric cooler (TEC), a microfan, and microcontroller is first applied to thermal management of high-power light-emitting diodes (LEDs). Its hardware is composed of microcontroller as a control core, K-type thermocouples as acquisition devices, and TEC and a microfan with heatsink as cooling vehicles. The experiment confirms that the LEDs substrate temperature can be controlled effectively, and indicates that the LED chips are operating reliably. Specifically, in high-temperature environments of 43 °C, the system can automatically drop to the low set temperature (30 °C) due to thermoelectric effect driven by TEC. Heat transfer analysis shows that maximum LED power cooled by the system is 106.7 W, and the total power consumption of the automatic cooling system is only 8.85 W. The automatic cooling system has a high cooling efficiency.

Blending Polyetheretherketone (PEEK) with Polyvinyl alcohol (PVA) is promising to obtain a composite scaffold combining the excellent biomechanical properties of PEEK and the remarkable degradability of PVA. However, the weak interfacial bonding between nonpolar PEEK and polar PVA would result in poor mechanical properties. In this study, owing to its unique amphiphilic properties, graphene oxide (GO) was employed to enhance the interfacial bonding between PEEK and PVA in PEEK/PVA scaffolds that were fabricated by laser 3D printing. On the one hand, the large π-conjugated structure of GO formed strong π-π interactions with the benzene rings in PEEK. On the other hand, the oxygen-containing groups of GO formed strong hydrogen bonds with the hydroxyl groups of PVA. As a result, the interfacial free energy between PEEK and PVA decreased from 37.4 to 29.6 mJ/m2 according to the harmonic-mean rule, and the PVA phase in PEEK matrix became much fine and uniform, indicating a reinforced interfacial bonding. Correspondingly, the strength and modulus of PEEK/PVA scaffolds increased by 97.16% and 147.06%, respectively, for a GO loading of 1%. Furthermore, the scaffolds exhibited good hydrophilicity and degradability, and promoted cell attachment and proliferation in vitro and osteogenic differentiation and bone regeneration in vivo.

Iron (Fe) has been highly anticipated as a bone implant material owing to the biodegradability and excellent mechanical properties, but limited by the slow degradation and poor bioactivity. In this study, novel Fe-palladium (Pd)-bredigite biocomposites were developed by selective laser melting aiming to improve both the degradation behavior and bioactivity of Fe. The results showed that most Pd formed Pd-rich intermetallic phases (IMPs) with a nearly continuous network while the bredigite phase was distributed at the grain boundaries. In addition, a large amount of much nobler IMPs formed micro-galvanic pairs with the Fe matrix, inducing tremendous micro-galvanic corrosion. The IMPs contained a high amount of Pd2+ with a high reduction potential, which further promoted the efficiency of micro-galvanic corrosion. Moreover, the rapid degradation of bredigite also facilitated the penetration of the corrosion medium. As a result, the Fe-4Pd-5bredigite biocomposite showed a uniform degradation with a rate that is 6 times that of Fe. Furthermore, the developed Fe-Pd-bredigite biocomposites also featured excellent bioactivity, cytocompatibility, and suitable mechanical properties as characterized by the rapid apatite deposition, normal proliferation of human osteoblast-like cells (MG-63), and comparable strength and microhardness with the native bone. Overall, this study opens a new avenue for improving both the degradation and bioactivity of Fe-based composites and may facilitate their applications as biodegradable implants for tissue/organ repair.

In this study, graphene oxide is incorporated into poly(vinyl alcohol) for the purpose of improving the mechanical properties. Nanocomposite scaffolds with an interconnected porous structure are fabricated by selective laser sintering.