Hongshui Wang

Ultra-broadband enhanced absorption of metal surfaces structured by femtosecond laser pulses

We investigate the enhanced absorption properties in a wavelength range of 0.2-25 microm for NiTi alloy targets structured by femtosecond laser pulses in air. Three different types of surface structures are produced with varying laser fluences. Measured reflectances through integrating sphere technique show that their couplings of incident electromagnetic irradiations are improved greatly over the broadband wavelength range. In particular, for coral-like micro-structures on the metal surfaces, approximate 90% absorption can be achieved from ultraviolet to mid-infrared region. Cut-off wavelengths of the enhanced absorption for the varied dimensional surface structures are determined experimentally. Chemical analysis by X-ray photoelectron spectroscopy indicates that blackness of metal surfaces is not attributed to the change in elemental composition. The physics of such remarkable absorption for the structured metal surfaces are discussed as well.

Surface microstructuring of Ti plates by femtosecond lasers in liquid ambiences: a new approach to improving biocompatibility

Microstructuring of Ti plates with femtosecond laser pulses is investigated in three different liquids. In these ambiences, complex microstructures with voids and islands are produced on the sample surfaces, whose feature sizes are controlled by the laser parameters. Through adopting supersaturated Hydroxyapatite suspension with higher incident laser fluences, it is for the first time to observe the firm deposition of biocompatible elements Ca-P on the microstructures. At lower laser fluence, only porous structure is present but without additional elements deposition. Both plasma-related ablation under the confinement of liquids and micro-bubbles striking are employed to discuss such structures formation. Tight combining elements Ca-P onto the structured surfaces provide a new way to improve the biocompatibility of body-embedded devices.

Femtosecond laser-induced micropattern and Ca/P deposition on Ti implant surface and its acceleration on early osseointegration.

Surface microstructure and chemical composition of the implant are very important for its osseointegration in vivo. In this paper, a hierarchical micropattern covered with calcium phosphate (Ca/P phase) was obtained on titanium (Ti) implant surface by femtosecond lasers (FSL) irradiation in hydroxyapatite suspension. The hierachical micropattern as well as Ca/P phase increased osteoblastic cell adhesion. Higher expression of osteogenic markers (osteocalcin, osteopontin, and runt related transcription factor-2) on the surface treated by FSL of 2.55 J/cm(2) indicated the favorable effect of laser treatment on cell differentiation. In vivo studies were carried out to evaluate the effect of laser treatment and Ca/P deposition on the osseointegration. It showed that the binding capacity between bone and FSL-treated Ti implants was obviously stronger than that between bone and polished or sand blasting and acid etching (SLA) Ti implants. Bone trabecula surrounded the FSL-treated implants without fibrous tissue after 8-week implantation. Also, higher bone mineral density was seen surrounding the FSL-treated implants. Our in vitro and in vivo studies demonstrated that the FSL induced micropattern and Ca/P phase had positive effects on the acceleration of early osseointegration of Ti implants with bone tissue.

Synergistic effects of hierarchical hybrid micro/nanostructures on the biological properties of titanium orthopaedic implants

A hierarchical hybrid micro/nanostructure was produced on the surface of titanium (Ti) implants by combined use of acid etching and anodic oxidation. The bioactivity of the modified Ti was evaluated by a simulated body fluid (SBF) soaking test and in vitro cell culture experiments. The results showed that the surface-modified Ti implants had a microstructure with enhanced surface roughness. There was also a nanostructure superimposed on the microstructure, forming a hierarchical hybrid micro/nanostructure. The modified Ti accelerated the Ca–P mineralization deposition on their surface in SBF, and promoted osteoblast adhesion, proliferation, and bone-related gene expression compared to the polished Ti and the Ti implants subjected only to acid etching or anodic oxidation, which was ascribed to the synergistic effects of both micro- and nanotopography generated. This study provides a simple and cost-effective approach to enhance the bioactivity and biocompatibility of orthopaedic implants, and points out the importance of both micro and nanotopography.

Simulation research of hot stamping and phase transition of automotive high strength steel

Abstract In order to establish the process specification of the hot stamping process for high strength steel components, which are largely used in the automobile industry, the characteristics of forming processes and the phase transition have been investigated. Based on a phase change model, a thermomechanical–metallurgical model for high strength steel has been established. In a multiphysical coupling calculation platform, the microstructure changes of ADVANCE1500 (22SiMnTiB) during its hot stamping process are obtained. Numerical results show that the finite element model is effective in simulation of hot forming process. Die gap and contact state between sheet and dies have considerable influence on the temperature distribution of the sheet. At the end of the process, U shaped parts at the bottom and sidewall areas have higher temperature, which leads to austenite–martensite transformation but not to a full level.

Biological properties of nanostructured Ti incorporated with Ca, P and Ag by electrochemical method

TiO2 nanotube arrays were synthesized on Ti surface by anodic oxidation. The elements of Ca and P were simultaneously incorporated during nanotubes growth in SBF electrolyte, and then Ag was introduced to nanotube arrays by cathodic deposition, which endowed the good osseointegration and antibacterial property of Ti. The bioactivity of the Ti surface was evaluated by simulated body fluid soaking test. The biocompatibility was investigated by in vitro cell culture test. And the antibacterial effect against Staphylococcus aureus was examined by the bacterial counting method. The results showed that the incorporation of Ca, P and Ag elements had no significant influence on the formation of nanotube arrays on Ti surface during electrochemical treatment. Compared to the polished or nanotubular Ti surface, TiO2 nanotube arrays incorporated with Ca, P and Ag increased the formation of bone-like apatite in simulated body fluid, enhanced cell adhesion and proliferation, and inhibited the bacterial growth. Based on these results, it can be concluded that the nanostructured Ti incorporated with Ca, P and Ag by electrochemical method has promising applications as implant material.

Preparation of Hydrophobic and Oleophilic Surface of 316 L Stainless Steel by Femtosecond Laser Irradiation in Water

An excellent hydrophobic and super-oleophilic surface on 316 L stainless steel was obtained by femtosecond laser irradiation in deionized water. Using lower laser fluence and scanning speed of femtosecond laser irradiation, a single stripe structure was fabricated and the corresponding contact angle to water and ethylene glycol was 127.2° and 19.6°, respectively. When laser fluence and scanning speeds increased, stripes, grooves, and holes structures were obtained on the surface and the corresponding water contact angles increased and ethylene glycol contact angles decreased, with a maximum water contact angle of 142.5° and minimum ethylene glycol contact angle of 6.4°.

Nano-hydroxyapatite/polyamide 6 scaffold as potential tissue engineered bone substitutes

Abstract In this study, nano-hydroxyapatite/polyamide 6 composite scaffold was prepared by phase separation and particle leaching combined method (PS/PL), and the scaffold, cultured with and without mesenchymal stem cells (MSCs), was investigated in vitro and in vivo. The scanning electron microscope photographs show a three-dimensional interconnected macroporosity of the scaffold. The compressive strength of the scaffold is 3˙27±0˙60 MPa is 81˙72±0˙68%. The biological results show that the scaffolds act as a template for the adhesion, growth, differentiation and proliferation of cells and have no negative effects on the MSCs in vitro. In the animal experiments, n-HA/PA6 scaffolds and MSCs cocultured scaffolds were implanted into the critical sized calvarial defect of rats respectively, to study their biocompatibility and osteogenesis in vivo. Both pure scaffolds and MSCs hybridised scaffolds exhibited favourable biocompatibility and osteogenesis. In contrast with pure scaffolds, the hybrid scaffolds can accelerate the bone reconstruction. These results indicate that n-HA/PA6 composite porous materials are suitable materials for bone tissue engineering and have the feasibility to be widely used in orthopaedics for clinical application.

Synthesis and cytotoxicity of carbon nanotube/hydroxyapatite in situ composite powders prepared by chemical vapour deposition

Abstract Carbon nanotube (CNT)/hydroxyapatite (HA) composite powders were successfully synthesised in situ by chemical vapour deposition of methane. The effects of different catalytic metals (Fe, Ni and Co) on yield, morphology and structure of CNTs were studied. The cytotoxicity of CNT/HA composite powders towards mouse fibroblast cells was investigated by in vitro cell culture test. The results show that Fe and Ni as catalysts are more favourable for the formation of CNT/HA composite powders than Co as catalyst, achieving excellent dispersion of CNTs in HA matrix, which indicates that these CNT/HA in situ composite powders can be directly applied to prepare bulk composite. The results of cytotoxicity test indicate that, compared with commercial CNT and CNT(Ni)/HA composite powders, the CNT(Fe)/HA in situ composite powder has no obvious cytotoxicity, which is more suitable to prepare CNT/HA composite for medical applications. Therefore, the method described in this paper is of great potential to realise the preparation of HA matrix composite with evenly dispersed CNTs, resulting in good mechanical and biological properties.

Biological and Mechanical Effects of Micro-Nanostructured Titanium Surface on an Osteoblastic Cell Line In vitro and Osteointegration In vivo

Hybrid micro-nanostructure implant surface was produced on titanium (Ti) surface by acid etching and anodic oxidation to improve the biological and mechanical properties. The biological properties of the micro-nanostructure were investigated by simulated body fluid (SBF) soaking test and MC3T3-E1 cell co-culture experiment. The cell proliferation, spreading, and bone sialoprotein (BSP) gene expression were examined by MTT, SEM, and reverse transcription-polymerase chain reaction (RT-PCR), respectively. In addition, the mechanical properties were evaluated by instrumented nanoindentation test and friction-wear test. Furthermore, the effect of the micro-nanostructure surface on implant osteointegration was examined by in vivo experiment. The results showed that the formation of bone-like apatite was accelerated on the micro-nanostructured Ti surface after immersion in simulated body fluid, and the proliferation, spreading, and BSP gene expression of the MC3T3-E1 cells were also upregulated on the modified surface. The micro-nanostructured Ti surface displayed decreased friction coefficient, stiffness value, and Young’s modulus which were much closer to those of the cortical bone, compared to the polished Ti surface. This suggested much better mechanical match to the surrounding bone tissue of the micro-nanostructured Ti surface. Furthermore, the in vivo animal experiment showed that after implantation in the rat femora, the micro-nanostructure surface displayed higher bonding strength between bone tissues and implant; hematoxylin and eosin (H&E) staining suggested that much compact osteoid tissue was observed at the interface of Micro-nano-Ti-bone than polished Ti-bone interface after implantation. Based on these results mentioned above, it was concluded that the improved biological and mechanical properties of the micro-nanostructure endowed Ti surface with good biocompatibility and better osteointegration, implying the enlarged application of the micro-nanostructure surface Ti implants in future.