Constructing core-shell structured BaTiO3@carbon boosts piezoelectric activity and cell response of polymer scaffolds

Polyvinylidene Fluoride Based Piezoelectric Composites with Strong Interfacial Adhesion via Click Chemistry for Self-Powered Flexible Sensors

Achieving relatively uniform dispersion in organic-inorganic composites with overwhelming differences in surface energy is a perennial challenge. Herein, novel eliminated polyvinylidene fluoride (EPVDF)/EPVDF functionalized barium titanate nanoparticles (EPVDF@BT) flexible piezoelectric nanogenerators (PENGs) with strong interfacial adhesion are developed via thermal stretching following sequential click chemistry. Thanks to the strong interfacial adhesion, the optimal PENGs containing ultra-high β-phase content (97.2%) exhibit not only optimized mechanical and dielectric behaviors but also excellent piezoelectric properties with high piezoelectric output (V = 10.7 V, I = 216 nA), reliable durability (8000 cycles), ultrafast response time (20 ms), and good sensitivity (2.09 nA kPa-1), far outperforming most reported PVDF-based composites. Furthermore, COMSOL finite element simulations (FEM) confirm that the elevated stress transfer efficiency induced by the strong interfacial adhesion is the main driving force for enhanced piezoelectric performances. For practical applications, self-powered PENGs can simply but stably capture mechanical energy, drive tiny electronic devices, and serve as potential multifunctional and durable sensors for detecting human physiological motions. This work opens a pioneering avenue to break the trade-offs between piezoelectric and other properties, which is of great importance for developing self-powered flexible sensors.

High output flexible polyvinylidene fluoride based piezoelectric device incorporating cellulose nanofibers/BaTiO3@TiO2 piezoelectric core-shell structure

Flexible composite film has gained increasing attention in the fields of wearable devices and portable electronic products. In this work, a novel core-shell structure of cellulose nanofibers/BaTiO3@TiO2 (CNF/BTO@TiO2) was synthesized with the assistant of the biological macromolecule material of cellulose nanofiber (CNF), in which the CNF can improve the stability and dispersibility of BaTiO3 (BTO) in the aqueous phase and elevate the integrity of the core-shell structure. The core-shell structure can reduce the agglomeration of fillers in polyvinylidene fluoride (PVDF) and improve the structural defects of the composite film. Meanwhile, the core-shell structure can promote the polarization of the electric dipole and the formation of β phase in PVDF due to the generated interface spatial polarization between the shell of TiO2 and the core of BTO. When the content of the core-shell structure was 5 wt%, the β phase content reaches 61.89 %, and the piezoelectric coefficient of composite film reaches 84.29 pm/V. Thus the maximum output open-circuit voltage (VOC) and short-circuit current (ISC) of the piezoelectric composite film is as high as 13.10 V and 464.3 nA. In addition, its excellent pressure sensing capability allows for its application in various flexible electronic devices.

Biomimetic-inspired piezoelectric ovalbumin/BaTiO3 scaffolds synergizing with anisotropic topology for modulating Schwann cell and DRG behavior

The treatment of peripheral nerve injury is a clinical challenge that tremendously affected the patients' health and life. Anisotropic topographies and electric cues can simulate the regenerative microenvironment of nerve from physical and biological aspects, which show promising application in nerve regeneration. However, most studies just unilaterally emphasize the effect of sole topological- or electric- cue on nerve regeneration, while rarely considering the synergistic function of both cues simultaneously. In this study, a biomimetic-inspired piezoelectric topological ovalbumin/BaTiO3 scaffold that can provide non-invasive electrical stimulation in situ was constructed by combining piezoelectric BaTiO3 nanoparticles and surface microtopography. The results showed that the incorporation of piezoelectric nanoparticles could improve the mechanical properties of the scaffolds, and the piezoelectric output of the scaffolds after polarization was significantly increased. Biological evaluation revealed that the piezoelectric topological scaffolds could regulate the orientation growth of SCs, promote axon elongation of DRG, and upregulate the genes expression referring to myelination and axon growth, thus rapidly integrated chemical-mechanical signals and transmitted them for effectively promoting neuronal myelination, which was closely related to peripheral neurogenesis. The study suggests that the anisotropic surface topology combined with non-invasive electronic stimulation of the ovalbumin/BaTiO3 scaffolds possess a promising application prospect in the repair and regeneration of peripheral nerve injury.

Scaffold-Based Poly(Vinylidene Fluoride) and Its Copolymers: Materials, Fabrication Methods, Applications, and Perspectives

Tissue engineering involves implanting grafts into damaged tissue sites to guide and stimulate the formation of new tissue, which is an important strategy in the field of tissue defect treatment. Scaffolds prepared in vitro meet this requirement and are able to provide a biochemical microenvironment for cell growth, adhesion, and tissue formation. Scaffolds made of piezoelectric materials can apply electrical stimulation to the tissue without an external power source, speeding up the tissue repair process. Among piezoelectric polymers, poly(vinylidene fluoride) (PVDF) and its copolymers have the largest piezoelectric coefficients and are widely used in biomedical fields, including implanted sensors, drug delivery, and tissue repair. This paper provides a comprehensive overview of PVDF and its copolymers and fillers for manufacturing scaffolds as well as the roles in improving piezoelectric output, bioactivity, and mechanical properties. Then, common fabrication methods are outlined such as 3D printing, electrospinning, solvent casting, and phase separation. In addition, the applications and mechanisms of scaffold-based PVDF in tissue engineering are introduced, such as bone, nerve, muscle, skin, and blood vessel. Finally, challenges, perspectives, and strategies of scaffold-based PVDF and its copolymers in the future are discussed.

Biophysical stimulation for bone regeneration using a chitosan/barium titanate ferroelectric composite

Herein we report the synthesis of a ferroelectric composed of chitosan (C)/barium titanate (BT) nanoparticles (NPs) with enhanced biocompatibility, non-toxicity, and piezoelectric behavior that can be advantageously used in biomedical applications. FTIR and SEM measurements were performed to assess the mechanism of interaction between the C matrix and BT NPs and their correlation with the biological responses. The dielectric measurements of the as-prepared composites reveal that incorporation of 50% BT NPs in the chitosan matrix leads to a steady increase of the dielectric constant as compared with neat chitosan films. The ferroelectric behavior of the sample was confirmed by the values of the loss factor (0.21-0.003) in the analyzed frequency range (10-1-106 Hz). This behavior suggests that ferroelectric C/BT nanocomposites can act as an active material that promotes accelerated bone regeneration.

Utilizing a High-Performance Piezoelectric Nanocomposite as a Self-Activating Component in Piezotronic Artificial Mechanoreceptors

Challenges such as poor dispersion and insufficient polarization of BaTiO3 (BTO) nanoparticles (NPs) within poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) composites have hindered their piezoelectricity, limiting their uses in pressure sensors, nanogenerators, and artificial sensory synapses. Here, we introduce a high-performance piezoelectric nanocomposite material consisting of P(VDF-TrFE)/modified-BTO (mBTO) NPs for use as a self-activating component in a piezotronic artificial mechanoreceptor. To generate high-performance piezoelectric nanocomposite materials, the surface of BTO is hydroxylated, followed by the covalent attachment of (3-aminopropyl)triethoxysilane to improve the dispersibility of mBTO NPs within the P(VDF-TrFE) matrix. We also aim to enhance the crystallization degree of P(VDF-TrFE), the efficiency characteristics of mBTO, and the poling efficiency, even when incorporating small amounts of mBTO NPs. The piezoelectric potential mechanically induced from the P(VDF-TrFE)/mBTO NPs nanocomposite was three times greater than that from P(VDF-TrFE) and twice as high as that from the P(VDF-TrFE)/BTO NPs nanocomposite. The piezoelectric potential generated by mechanical stimuli on the piezoelectric nanocomposite was utilized to activate the synaptic ionogel-gated field-effect transistor for the development of self-powered piezotronics artificial mechanoreceptors on a polyimide substrate. The device successfully emulated fast-adapting (FA) functions found in biological FA mechanoreceptors. This approach has great potential for applications to future intelligent tactile perception technology.

Porous Titanium Scaffolds with Mechanoelectrical Conversion and Photothermal Function: A Win-Win Strategy for Bone Reconstruction of Tumor-Resected Defects

Bone metastases severely threaten the lives of patients. Although surgical treatment combined with adjuvant chemotherapy significantly improves the survival rate of patients, tumor recurrence, or metastasis after surgical resection and bone defects caused by surgical treatment remain major challenges for clinicians. Given the abovementioned clinical requirements, barium titanate-containing iron-coated porous titanium alloy scaffolds have been proposed to promote bone defect repair and inhibit tumor recurrence. Fortunately, in vitro and in vivo experimental research confirms that barium titanate containing iron-coated porous titanium alloy scaffolds promote osteogenesis and bone reconstruction in defect repair via mechanoelectric conversion and inhibit tumor recurrence via photothermal effects. Furthermore, the underlying and intricate mechanisms of bone defect repair and tumor recurrence prevention of barium titanate-containing iron-coated porous titanium alloy scaffolds are explored. A win-win strategy for mechanoelectrical conversion and photothermal functionalization provides promising insights into bone reconstruction of tumor-resected defects.

Computational design and evaluation of the mechanical and electrical behavior of a piezoelectric scaffold: a preclinical study

Piezoelectric scaffolds have been recently developed to explore their potential to enhance the bone regeneration process using the concept of piezoelectricity, which also inherently occurs in bone. In addition to providing mechanical support during bone healing, with a suitable design, they are supposed to produce electrical signals that ought to favor the cell responses. In this study, using finite element analysis (FEA), a piezoelectric scaffold was designed with the aim of providing favorable ranges of mechanical and electrical signals when implanted in a large bone defect in a large animal model, so that it could inform future pre-clinical studies. A parametric analysis was then performed to evaluate the effect of the scaffold design parameters with regard to the piezoelectric behavior of the scaffold. The designed scaffold consisted of a porous strut-like structure with piezoelectric patches covering its free surfaces within the scaffold pores. The results showed that titanium or PCL for the scaffold and barium titanate (BT) for the piezoelectric patches are a promising material combination to generate favorable ranges of voltage, as reported in experimental studies. Furthermore, the analysis of variance showed the thickness of the piezoelectric patches to be the most influential geometrical parameter on the generation of electrical signals in the scaffold. This study shows the potential of computer tools for the optimization of scaffold designs and suggests that patches of piezoelectric material, attached to the scaffold surfaces, can deliver favorable ranges of electrical stimuli to the cells that might promote bone regeneration.

A spatiotemporal drug release scaffold with antibiosis and bone regeneration for osteomyelitis

INTRODUCTION

Scaffolds loaded with antibacterial agents and osteogenic drugs are considered essential tools for repairing bone defects caused by osteomyelitis. However, the simultaneous release of two drugs leads to premature osteogenesis and subsequent sequestrum formation in the pathological situation of unthorough antibiosis.

OBJECTIVES

In this study, a spatiotemporal drug-release polydopamine-functionalized mesoporous silicon nanoparticle (MSN) core/shell drug delivery system loaded with antibacterial silver (Ag) nanoparticles and osteogenic dexamethasone (Dex) was constructed and introduced into a poly-l-lactic acid (PLLA) scaffold for osteomyelitis therapy.

METHODS

MSNs formed the inner core and were loaded with Dex through electrostatic adsorption (MSNs@Dex), and then polydopamine was used to seal the core through the self-assembly of dopamine as the outer shell (pMSNs@Dex). Ag nanoparticles were embedded in the polydopamine shell via an in situ growth technique. Finally, the Ag-pMSNs@Dex nanoparticles were introduced into PLLA scaffolds (Ag-pMSNs@Dex/PLLA) constructed by selective laser sintering (SLS).

RESULTS

The Ag-pMSNs@Dex/PLLA scaffold released Ag+ at the 12th hour, followed by the release of Dex starting on the fifth day. The experiments verified that the scaffold had excellent antibacterial performance against Escherichia coli and Staphylococcus aureus. Moreover, the scaffold significantly enhanced the osteogenic differentiation of mouse bone marrow mesenchymal stem cells.

CONCLUSION

The findings suggested that this spatiotemporal drug release scaffold had promising potential for osteomyelitis therapy.

Ultrasound-mediated piezoelectric nanoparticle modulation of intrinsic cardiac autonomic nervous system for rate control in atrial fibrillation

Rate control is a cornerstone of atrial fibrillation treatment. Barium titanate nanoparticles (BTNPs) are piezoelectric nanomaterials that can generate local electromagnetic fields under ultrasound activation, stimulating nearby neuronal tissue. This study aimed to modulate the inferior right ganglionated plexus (IRGP) of the heart and reduce the ventricular rate during rapid atrial pacing (RAP)-induced atrial fibrillation using ultrasound-mediated BTNPs. Adult male beagles were randomly divided into a phosphate-buffered saline (PBS) group (n = 6) and a BTNP group (n = 6). PBS or nanoparticles were injected into the IRGP of both groups before RAP. The biological safety of the material was evaluated according to electrophysiology recordings, thermal effects and level of inflammation. Compared to the PBS group, the BaTiO₃ piezoelectric nanoparticle group had reduced ventricular rates in the sinus rhythm and atrial fibrillation models after stimulating the IRGP by applying ultrasound. In addition, transient stimulation by BTNPs did not lead to sustained neuronal excitation in the IRGP. The activation of the BTNPs did not induce inflammation or thermal damage effects in the IRGP. Ultrasound-mediated BTNP neuromodulation can significantly reduce the ventricular rate by stimulating the IRGP. Thus, ultrasound-mediated BTNP neuromodulation is a potential therapy for atrial fibrillation rate control.

Modified Stranski-Krastanov Growth of Amino Acid Arrays toward Piezoelectric Energy Harvesting

Biomolecule-based piezoelectric nanostructures emerged as a new class of energy-converse materials, and designing tailored piezoelectric amino acid arrays is essential to achieve efficient electrical-mechanical coupling and fulfill their application potential. However, the controlled growth of amino acid nanostructures is still challenging due to the limited understanding of their growth mechanism. Herein, we base on the Stranski-Krastanov (S-K) growth mode and propose a mechanism for the growth of ordered amino acid array structures via physical vapor deposition. The growth of vertical valine sheet arrays is examined by changing the substrate temperature, chamber pressure, and source-substrate distance, and a "layer-plus-sheet" growth process is revealed. The modified S-K growth mode is applied to fabricate other amino acid nanostructures like leucine and isoleucine. The growth mode not only explains the formation of uniform and controllable morphology of amino acid structures but also leads to the significant enhancement of their piezoelectric properties. The maximal effective piezoelectric constant of valine sheets is 11.4 pm V^-1, which approaches its highest predicted value. The output voltage of the valine array-based nanogenerator is ∼4.6 times the output voltage of the valine powder-based nanogenerator. This work provides new insights into the growth mechanism of ordered piezoelectric amino acid arrays, making them promising candidates for applications in wearable or implantable electronic devices.

A Codispersed Nanosystem of Silver-anchored MoS2 Enhances Antibacterial and Antitumor Properties of Selective Laser Sintered Scaffolds

Tumor recurrence and bacterial infection are common problems during bone repair and reconstruction after bone tumor surgery. In this study, silver-anchored MoS₂ nanosheets (Ag@PMoS₂) were synthesized by in situ reduction, then a composite polymer scaffold (Ag@PMoS₂/PGA) with sustained antitumor and antibacterial activity was successfully constructed by selective laser sintering technique. In the Ag@PMoS₂ nanostructures, silver nanoparticles (Ag NPs) were sandwiched between adjacent MoS₂ nanosheets (MoS₂ NSs), which restrained the restacking of the MoS₂ NSs. In addition, the MoS₂ NSs acted as steric hindrance layers, which prevented the aggregation of Ag NPs. More importantly, MoS₂ NSs can provide a barrier layer for Ag NPs, hindering Ag NPs from reacting with the external solution to prevent its quick release. The results showed that Ag@PMoS₂/PGA scaffolds have stronger photothermal effect and antitumor function. Meanwhile, the Ag@PMoS₂/PGA scaffolds also demonstrated slow control of silver ion (Ag⁺) release and more efficient long-term antibacterial ability. Besides, composite scaffolds have been proved to kill the MG-63 cells by inducing apoptosis and inhibit bacterial proliferation by upregulating the level of bacterial reactive oxygen species. This kind of novel bifunctional implants with antitumor and antibacterial properties provides better choice for the artificial bone transplantation after primary bone tumor resection.

Comparative review of piezoelectric biomaterials approach for bone tissue engineering

Bone as a minerals' reservoir and rigid tissue of the body generating red and white blood cells supports various organs. Although the self-regeneration property of bone, it cannot regenerate spontaneously in severe damages and still remains as a challenging issue. Tissue engineering offers several techniques for regenerating damaged bones, where various biomaterials are examined to fabricate scaffolds for bone repair. Piezoelectric characteristic plays a crucial role in repairing and regenerating damaged bone by mimicking the bone niche behavior. Piezoelectric biomaterials show significant potential for bone tissue engineering. Herein we try to have a comparative review on piezoelectric and non-piezoelectric biomaterials used in bone tissue engineering, classified them, and discussed their effects on implanted cells and manufacturing techniques. Especially, Polyvinylidene fluoride (PVDF) and its composites are the most practically used piezoelectric biomaterials for bone regeneration. PVDF and its composites have been summarized and discussed to repair damaged bone tissues.

Combining Solid-State Shear Milling and FFF 3D-Printing Strategy to Fabricate High-Performance Biomimetic Wearable Fish-Scale PVDF-Based Piezoelectric Energy Harvesters

High-performance flexible piezoelectric polymer-ceramic composites are in high demand for increasing wearable energy-harvesting applications. In this work, a strategy combining solid-state shear milling (S³M) and fused filament fabrication (FFF) 3D-printing technology is proposed for the fabrication of high-performance biomimetic wearable piezoelectric poly(vinylidene fluoride) (PVDF)/tetraphenylphosphonium chloride (TPPC)/barium titanate (BaTiO₃) nanocomposite energy harvesters with a biomimetic fish-scale-like metamaterial. The S³M technology could greatly improve the dispersion of BaTiO₃ sub-micrometer particles and the interfacial compatibility, resulting in better processability and piezoelectric performance of the nanocomposites. Typically, the FFF 3D printed energy harvester incorporating 30 wt % BaTiO₃ showed the highest piezoelectric outputs with an open-circuit voltage of 11.5 V and a short-circuit current of 220 nA. It could hence drive nine green LEDs to work normally. In addition, a 3D-printed biomimetic wearable energy harvester inspired by an environmentally adaptive fish-scale-like metamaterial was further fabricated. The fish-scale-like energy harvester could harvest energy through different deformation motions and successfully recharge a 4.7 μF capacitor by being mounted on a bicycle tire and the tire's rolling. This work not only provides a 3D printing strategy for designing diversified and complex geometric structures but also paves the way for further applications in flexible, wearable, self-powered electromechanical energy harvesters.

Magnetostrictive alloys: Promising materials for biomedical applications

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.

Construction of a stereocomplex between poly(D-lactide) grafted hydroxyapatite and poly(L-lactide): toward a bioactive composite scaffold with enhanced interfacial bonding

The poly(L-lactide) (PLLA)/hydroxyapatite (HAP) composite scaffold is expected to combine the favorable compatibility and processability of PLLA with the excellent bioactivity and osteoconductivity of HAP. Unfortunately, the poor interfacial bonding between PLLA and HAP leads to a deterioration in mechanical properties. In this study, poly(D-lactide) (PDLA) was grafted onto the surface of HAP nanoparticles (g-HAP), and then g-HAP was incorporated into PLLA to improve interfacial bonding by stereocomplexation in a scaffold fabricated via selective laser sintering (SLS). The results showed that HAP nanoparticles were grafted with PDLA at a grafting rate of 8.72% by ring-opening polymerization through chemical bonding in the presence of the hydroxyl groups of HAP. The grafted PDLA formed an interfacial stereocomplex with PLLA via an intertwined spiral structure ascribed to their antiparallel and complementary configuration under the action of hydrogen bonding. Consequently, the tensile strength and modulus of the PLLA/g-HAP scaffold increased by 86% and 69%, respectively, compared to those of the PLLA/HAP scaffold. In addition, the scaffold displayed good bioactivity by inducing apatite nucleation and deposition and possessed good cytocompatibility for cell adhesion, growth and proliferation.

Rivet-Inspired Modification of Carbon Nanotubes by In Situ-Reduced Ag Nanoparticles To Enhance the Strength and Ductility of Zn Implants

Zinc shows promise for bone repair applications, while its strength and ductility require to be improved. Carbon nanotubes (CNTs) are exceptional reinforcements due to their superior strength, ultrahigh Young's modulus, and large aspect ratio. However, their strong agglomeration and weak interfacial bonding with the matrix are key bottleneck problems restricting the reinforcing effect. In this study, Ag nanoparticles were in situ reduced on CNTs and then the CNT@Ag powders were used to prepare Zn-CNT@Ag implants by laser powder bed fusion. Results showed that Ag reacted with Zn to form a "knot"-like AgZn₃ phase. It had the same lattice structure (HCP) with Zn, which indicated a good lattice matching with the matrix, thus improving the dispersion of CNTs. More significantly, the knot played a "rivet" role and enhanced the load transfer capacity, which advantaged the CNT strengthening effects by assisting in transferring the load. Moreover, it enhanced the heterogeneous nucleation effects during solidification, which weakened the texture strength of the matrix and thus increased the ductility by improving the sliding capacity. The compressive yield strength, ultimate tensile strength, and elongation of the Zn-CNT@Ag implant were increased by 22, 26, and 17% in comparison to Zn-CNTs. Moreover, the Zn-CNT@Ag implant exhibited favorable antibacterial activity with a bacterial inhibition rate of 87.79%. Additionally, it also exhibited a suitable degradation rate and acceptable biocompatibility.

Laser Additively Manufactured Iron-Based Biocomposite: Microstructure, Degradation, and In Vitro Cell Behavior

A too slow degradation of iron (Fe) limits its orthopedic application. In this study, calcium chloride (CaCl2) was incorporated into a Fe-based biocomposite fabricated by laser additive manufacturing, with an aim to accelerate the degradation. It was found that CaCl2 with strong water absorptivity improved the hydrophilicity of the Fe matrix and thereby promoted the invasion of corrosive solution. On the other hand, CaCl2 could rapidly dissolve once contacting the solution and release massive chloride ion. Interestingly, the local high concentration of chloride ion effectively destroyed the corrosion product layer due to its strong erosion ability. As a result, the corrosion product layer covered on the Fe/CaCl2 matrix exhibited an extremely porous structure, thus exhibiting a significantly reduced corrosion resistance. Besides, in vivo cell testing proved that the Fe/CaCl2 biocomposite also showed favorable cytocompatibility.

Laser-Sintered Mg-Zn Supersaturated Solid Solution with High Corrosion Resistance

Solid solutions of Zn as an alloy element in Mg matrixes are expected to show improved corrosion resistance due to the electrode potential being positively shifted. In this study, a supersaturated solid solution of Mg-Zn alloy was achieved using mechanical alloying (MA) combined with laser sintering. In detail, supersaturated solid solution Mg-Zn powders were firstly prepared using MA, as it was able to break through the limit of phase diagram under the action of forced mechanical impact. Then, the alloyed Mg-Zn powders were shaped into parts using laser sintering, during which the limited liquid phase and short cooling time maintained the supersaturated solid solution. The Mg-Zn alloy derived from the as-milled powders for 30 h presented enhanced corrosion potential and consequently a reduced corrosion rate of 0.54 mm/year. Cell toxicity tests confirmed that the Mg-Zn solid solution possessed good cytocompatibility for potential clinical applications. This study offers a new strategy for fabricating Mg-Zn solid solutions using laser sintering with MA.

Pre-oxidation induced in situ interface strengthening in biodegradable Zn/nano-SiC composites prepared by selective laser melting

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Zn/nano-SiC biocomposites were prepared via pre-oxidation and selective laser melting.

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In situ reaction improved the interface bonding between nano-SiC and the Zn matrix.

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The improved interfacial bonding enhanced the mechanical properties of the biocomposite.

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The biocomposite exhibited favorable biocompatibility on cell proliferation and adhesion.

Introduction

Nano-SiC has attracted great attention as ceramic reinforcement in metal matrix composites, but the weak interface bonding between them remains a bottleneck for efficient strengthening.

Objective

In this study, pre-oxidation treatments and selective laser melting (SLM) were employed to prepare Zn/nano-SiC biocomposites with strengthened interface bonding via in situ reaction.

Methods

Nano-SiC and Zn powders were pre-oxidized respectively, and then used to prepare Zn/nano-SiC biocomposites via SLM. The powder microstructure, and the interface characteristics and mechanical properties of the biocomposites were investigated. The degradation properties and cell response were analyzed to evaluate their feasibility for orthopedic applications.

Results

The results indicated that the pre-oxidation treatments generated a uniform oxide layer on the surface of both nano-SiC and Zn particles and the thickness of the oxide layer increased with pre-oxidation temperature. During the SLM process, the oxide layers not only improved the metal-ceramic wettability by reducing interface energy, but also induced in situ reaction to form chemical bonding between the Zn matrix and nano-SiC, thereby improving the interface bonding. Consequently, the Zn biocomposite reinforced by nano-SiC with a pre-oxidation temperature of 1000 °C (ZS1000 biocomposite) exhibited more transgranular fracture and significantly enhanced compressive yield strength of 171.5 MPa, which was 31.6% higher than that of the Zn biocomposite reinforced by nano-SiC without pre-oxidation. Moreover, the ZS1000 biocomposite presented slightly accelerated degradation which might be ascribed to the facilitated electron transfer by the interface product (Zn₂SiO₄). In addition, the ZS1000 biocomposite also showed appropriate biocompatibility for MG-63 cell adhesion, growth, and proliferation.

Conclusion

This study shows the potential practical applicability for the preparation of Zn-based biocomposites with strong interface bonding and mechanical properties for orthopedic applications.

Silver-doped bioglass modified scaffolds: A sustained antibacterial efficacy

Implant-related bacterial infection is a serious complication, which even causes implant failure. Silver (Ag) nanoparticles are broadly used antibacterial agents due to their excellent antibacterial ability and broad-spectrum bactericidal property. However, the significance of burst release cannot be entirely ignored. In this study, Ag doped mesoporous bioactive glasses (Ag-MBG) nanospheres were synthesized using modified Stöber method, then incorporated into poly L-lactic acid (PLLA) matrix to prepare the composite scaffolds via selective laser sintering (SLS) technology. Herein, Mesoporous bioactive glasses (MBG) sol had many negatively-charged silicon hydroxyl groups, which could adsorb positively-charged Ag ions by electrostatic interaction and eventually form Si-O-Ag bonds into MBG. Moreover, MBG promoted osteoblast colonization due to its continuous release of Si ions. The results showed the Ag-MBG/PLLA scaffold could sustainedly release Ag ions for 28 days, and exhibited significantly antibacterial ability against Escherichia coli, its bacterial inhibition rate was over 80%. In addition, the composite scaffold also showed good cytocompatibility. It may be concluded that the prepared Ag-MBG/PLLA scaffold has great potential to repair implant-associated bone infection.

Fabrication of PVDF/BaTiO3/CNT Piezoelectric Energy Harvesters with Bionic Balsa Wood Structures through 3D Printing and Supercritical Carbon Dioxide Foaming

Piezoelectric energy harvesters have received widespread attention in recent decades due to their inimitable electrical energy conversion methods. However, traditional polymer/piezoceramic materials and 2D thin-film structures have limited output performance, making them difficult to be efficiently applied in the collection of discrete mechanical energy. Here, new ternary composite powders were successfully developed by the ultrasonic coating method, and array structural devices with the construction of micropores were prepared using selective laser sintering (SLS) and supercritical carbon dioxide foaming (Sc-CO₂) technologies. Coating carbon nanotubes improved the polarization efficiency of poly(vinylidene fluoride)/barium titanate (PVDF/BaTiO₃) composites, which made it easy to perfectly combine the BaTiO₃ piezoelectric constant and the flexibility of PVDF, promoting d₃₃ from 0.7 to 2.6 pc/N. In addition, simulations and experiments simultaneously proved that SLS parts with high array densities amplified piezoelectric outputs because of a greater compression deformation in the vertical direction. Meanwhile, under the synergistic effect of SLS and Sc-CO₂, 3D bionic balsa wood structure foams were successfully fabricated, which took advantage of the normal space, expanded the stress-strain effect, and improved the piezoelectric output capability. Excitingly, the prepared foam could directly produce 19.3 V and 415 nA piezoelectric output to charge a 1 μF commercial capacitor to 5.03 V within 180 s, which surpassed most of the PVDF piezoelectric energy harvesters reported thus far. This work has an excellent innovative and practical value in enriching the types of piezoelectric materials for SLS 3D printing and the design of 3D piezoelectric structures.

Polydopamine-decorated black phosphorous to enhance stability in polymer scaffold

Black phosphorous (BP) is recognized as an effective reinforcement for polymer scaffold because of its excellent mechanical property and biocompatibility. Nevertheless, its poor stability in physiological environment limits its application in bone repair. In this work, BP was modified with dopamine by self-polymerization approach (donated as BP@PDA) to improve its stability, and then was introduced into poly-L-lactic acid (PLLA) scaffold fabricated by selective laser sintering technology. Results showed the compressive and tensile strength of PLLA/BP@PDA scaffold were improved by 105% and 50%, respectively. The enhanced strength was ascribed to the increased stability of BP and the improved compatibility of BP@PDA with PLLA matrix after modifying with polydopamine. Simultaneously, the bioactivity of PLLA scaffold was significantly improved. It was attributed to that BP@PDA provided the sustained source ofPO43-ions which could capture Ca²⁺ions from physiological medium to facilitatein situbiomineralization, thereby promoting cell adhesion, proliferation and differentiation. This study demonstrated the great potential of BP@PDA in bone repair.