Papers by Author: L. Zheng

Abstract: Tool material has been one of the focuses in tool research. Diamond and cubic boron nitride (c-BN) are materials of exceptional and very similar properties that make them extremely valuable not only for the aesthetics of diamond. C-BN is a material synthesized rather recently that has rapidly spurred technological and scientific interest. Presently, both materials have found commercial applications. There is still a long way for the practical application of cBN film. The main problems are such as adhesion, thickness, purity, nucleating, and growth mechanism. We will develop a new way of DC plasma jet CVD way to synthesis the cBN film. The deposition of cBN films can be performed in a DC jet plasma CVD reactor by using an Ar-N2-BF3-H2 gas mixture, on the basis of deposition of diamond has been achieved.

Abstract: With good biocompatibility, collagen is often used in cartilage tissue engineering. Collagen/alginate composite was hoped to improve the poor mechanical property of pure collagen but the biocompatibity was decreased. In this study, hydroxyapatite (HA) particles were used to get collagen/alginate/HA (CAHA) composite film to enhance the bioactivity properties. The bioactivity of the composite was investigated by in vitro co-culture with chondrocytes. During the 6-day cell culture in vitro, the composite showed a significant improvement in promoting proliferation and maintaining morphology/phenotype of the chondrocytes over collagen/alginate composite by MTT, SEM, fluorescent and immunohistochemical assays. Cytocompatibility and cytoviablility of CAHA even come up to that of collagen film alone. The results indicated that the composite film may provide an appropriate environment for the proliferation and maintaining the morphology and phenotype of chondrocytes and have a potential clinical application in the cartilage tissue engineering field.

Abstract: Fixation nail systems , such as DHS, DCS and the standard Gamma-nail, are widely applied for the 31-A2 intertrochanteric unstable fractures treatment, but which one would be of more curative effect is still remained as a disputed problem. In this work, precise femur model with 31-A2 fracture was rebuilt based on the CT data, and fixation nail models were built by CAD. By the means of finite element analysis (FEA), the biomechanical data of femur and nail systems were achieved under typical loading. The results show that under the same load, the maximal stresses on the fracture sections for DCS, DHS and Gamma nail systems are 48MPa, 24MPa and 19MPa, separately; and the directional deformation is the highest with DCS fixation systems, while lowest with Gamma nail fixation system. Considering the mechanical safety, Gamma nail is more suitable for 31-A2 intertrochanteric unstable fractures treatment.

Abstract: Stress concentration is one of the main mechanical problems leading to the failure of clinical application for osteointegrated implant of percutaneous osteointegrated prosthesis, which is especially marked for higher amputated leg prosthesis. Traditionally design was composed of only the distal part. To improve the biomechanical safety, a new design with the lag part similar to the lag screw was introduced. Based on CT scan data, relatively accurate model of femur for finite element analysis (FEA) were obtained. The FEA results with the new implant demonstrated that compared to traditional design, the declination of bone stress peak ranged from 15.68% to 28.67%, perpendicular deformation from 34.73% to 72.16%, and maximal stress of implant from 14.51% to 23.36% with the increasing of loads from 3750N to 2000N. So the new design of osteointegrated implant would be more secure mechanically, in the case of higher amputated leg attachment.

Abstract: Biological sealing is a key factor for successful development of percutaneous device (PD). A new device with arc-perforated flange as subcutaneous part and groove-shaped percutaneous part, was intended to improve integration of soft tissue and implant. Material and surface properties are known to have great impact on tissue-implant integration. To understand how a material and its surface property can influence tissue reaction, and to find the appropriate material for PD fabrication, five different kinds of materials were prepared for in vivo animal tests with corresponding histological evaluation. Results revealed that a more stable junction was formed between the soft tissue and HA coated titanium implant than other combinations.

Abstract: Stress shielding, which occurred always around traditional one part implant applied for prosthetic artificial lower limb attachment, would cause osteoporosis and thus result in the loose and extrusion, and then the malfunction of the implant. To improve the structure of the implant, a new type of implant—multi-part implant was developed in this article. Based on CT data and under the maximal load during a normal walking cycle, 3D finite element analysis (FEA) was carried out to analyze the stress of bone around the new implant in three cases of distally truncated femur at high position、middle-position and low-position. Results reveal that stress shielding and stress concentration under the new type of implant reduced effectively compared with the traditional one-part implant, and the stress distribution is much close to the natural bone. Application for distally truncated femur at middle-position and low-position was much better, while stress concentration was marked at high-position. Meanwhile, the stability in vivo can also be maintained with the multi-part implant. The new implant is promising applied for prosthetic limb.