压电陶瓷的生物听效应

本文探索一种新的简便方法，将压电陶瓷膜片植入耳蜗，利用材料的压电效应，直接将声信号变成电信号，刺激听神经产生听觉，取代价格昂贵、结构复杂的电子耳蜗，使聋耳重新获得听力。这将造福于几百万全聋病人。为此，我们找到一种铌酸盐压电陶瓷，其稳定性好、优值高、频率常数大、生物相容性好。制成厚膜小片植入爆震致聋的１５只豚鼠耳蜗后，聋耳听力提高４０－５０ｄＢ。显示压电陶瓷良好的生物听效应，有可能发展成新一代的人工     

压电型人工耳蜗的实验研究

系统研究了不同特性的压电陶瓷植入耳蜗及其植入位置对听阈变化的影响，实验结果表明，植入材料的机电耦合系数和电容越大，听阈下降越明显；陶瓷片置于鼓介中内侧贴于螺旋神经表面成功率最高。充分证实了压电陶瓷片植入耳蜗可模拟毛细胞进行声电转换，刺激听神经引起听觉，提高聋耳的呼力这一新构想是成功的。     

水泥基压电复合材料的研究进展

综述了水泥基压电复合材料的研究进展.对于0-3型水泥基压电复合材料,压电陶瓷相的性能、复合材料的制备工艺以及微观结构等对其压电及介电性能有重要影响.压电陶瓷相含量越高、粒度越大,复合材料的压电响应就越大.提高极化电压有助于增强复合材料的压电响应.增加成型压力可提高复合材料微观结构的致密性,从而提高压电性能.总结了压电陶瓷的体积分数、形貌以及环境湿度与1-3型水泥基压电复合材料的性能关系,介绍了2-2型水泥基压电复合材料的传感效应及驱动效应的相关研究成果,最后展望了该领域的发展前景.     

缺陷偶极子调控铅基钙钛矿压电陶瓷性能的研究进展

压电陶瓷作为一种可以实现机械能和电能之间相互转换的功能陶瓷材料,广泛应用于传感器、制动器、超声换能器、医学超声成像及发动机燃油喷射系统等领域.在压电陶瓷中,元素掺杂可以有效调控陶瓷的电学性能,伴随掺杂而产生的缺陷偶极子对压电陶瓷性能有着显著而独特的影响.因此研究缺陷偶极子对压电陶瓷性能的调控机理,有助于理解压电陶瓷诸多物理现象的内在成因,譬如老化、疲劳等.通过元素掺杂引入的氧空位会导致钙钛矿结构的压电陶瓷产生缺陷偶极子,而缺陷偶极子与自发极化之间的耦合效应会影响陶瓷的铁电响应行为,从而使得压电陶瓷出现束腰电滞回线和偏移电滞回线等特征.另外由于陶瓷中氧空位的扩散速率很低,使得缺陷偶极子极化方向趋于稳定,进而抑制极化旋转和限制畴壁运动,有助于提高压电陶瓷的机械品质因数.尽管有大量研究通过缺陷偶极子调控压电陶瓷的宏观性能使其能够满足不同的应用需求,然而由于压电陶瓷为多晶材料,其内部晶粒取向各异且存在复杂的铁电畴结构,压电陶瓷中缺陷偶极子在形成过程中的微观机理与其具体形态以及缺陷偶极子对压电陶瓷性能的具体作用机理仍有待深入研究.此外,压电陶瓷在高驱动场下的高功率特性对机电设备的实际设计具有重要意义,因此缺陷偶极子对压电陶瓷高功率特性的影响也值得关注.本文从氧空位诱导缺陷偶极子的形成及其表征手段、缺陷偶极子对铅基压电陶瓷电滞回线的影响和不同受主掺杂对铅基压电陶瓷机械品质因数的影响出发,论述了缺陷偶极子与压电陶瓷自发极化耦合效应引发的偏移和束腰奇异电滞回线特征,揭示了缺陷偶极子主要通过抑制极化旋转和限制畴壁运动提高机械品质因数的机理.然而关于缺陷偶极子的形态、与非四方相间的耦合关系以及缺陷偶极子对压电陶瓷高功率特性的影响等问题仍需进一步的研究.     

周期铁电畴压电陶瓷的制备工艺和频谱特性

采用了半导体光刻工艺、压电陶瓷极化工艺相结合的方法制备了多晶压电陶瓷周期畴结构。设计了周期极化所用高电压的脉冲波形、脉冲极化电压、脉冲宽度和脉冲个数。通过频谱分析可以得知:周期铁电畴压电陶瓷厚度切变振动的谐振频率决定于压电陶瓷周期铁电畴的半周期厚度,而不是决定于压电陶瓷的总厚度。周期铁电畴压电陶瓷厚度切变振动的谐振频率相应得到了提高,并且在其附近的Cs值达到了负值。     

0-3型PZN-PZT/PVDF压电复合材料的制备工艺条件优化

采用固相法合成了性能良好的PZN-PZT陶瓷粉体.将压电陶瓷粉体分散于PVDF基体中,制备了0-3型PZN-PZT/PVDF压电复合材料.研究了复合材料的复合工艺、极化参数与压电陶瓷的含量对复合材料压电性能的影响.结果表明,溶液混合工艺较好,且当极化电场强度为6kV·mm-1、温度为110℃进行极化20min时,陶瓷粉体质量分数为90%的复合材料的压电性能最好,压电常数d33值达35.9 pC·N-1.     

周期铁电畴压电陶瓷的制备和频谱特性研究

研究了复合结构的周期铁电畴压电陶瓷以及通过外加电场反向极化法制 备的周期铁电畴压电陶瓷的厚度切变模式. 分析了两种方法制备的周期铁电畴 压电陶瓷的频谱特性, 得出了铁电畴周期结构可以很好地抑制来源于纵向或径 向振动的高次泛音的不良影响和通过外加电场反向极化法制备小周期铁电畴提 高厚度切变模式谐振频率的方法, 从而可以通过调整周期大小制备出在一定频 率范围内呈现出具有感性的压电陶瓷.     

压电陶瓷极化特性研究

使用DP-5型介电谱仪,测量由压电陶瓷材料制作的蜂鸣器的介电频率特性,验证理论猜测。实验测出压电陶瓷的极化方式与极化率与外场频率有关,随着频率的增加,压电陶瓷的离子位移极化率、电介质分子取向极化的极化率将减小,最终表现为相对介电常数减小。实验结果与理论猜测吻合。     

新型旋转式压电惯性电机振子的冲击振动分析

新型旋转式压电惯性电机,是一种利用压电双晶片振子作为驱动元件,利用锯齿波作为激励电信号产生惯性冲击力的旋转电机。本文研究压电惯性电机振子在pzt元件激励下的冲击受迫响应。推导出了压电陶瓷片两端电压响应方程,以及压电振子梁的冲击受迫响应方程。分析了激励信号频率对振子梁端部响应的影响规律。同时,分析了不同激励信号占空比情况下振子梁端部响应变化规律,以及结构参数对电机驱动力矩的影响规律。分析了提高电机驱动力矩的有效途径。     

北京大学工学院在压电材料领域取得突破性进展

正工学院力学与工程科学系李法新课题组在压电材料领域取得突破性进展,他们提出了一种周期正交的极化方法,将目前最常用的PZT压电陶瓷中的非线性畴变应变变得可逆,实现了约0.6%的超大致动应变,是传统PZT压电陶瓷的4倍。压电陶瓷致动器具有响应速度快、位移精度高、控制方便(电控)、体积小等优势,一直在致动器领域占据着主导地位。目前应用的压电致动器主要由锆钛酸铅(PZT)陶瓷制     

人工种植牙材料及表面处理的研究进展

牙齿缺失是较为常见的口腔问题,牙齿缺失不仅影响患者的面部美观,还将对患者的生理及心理造成较大影响,进而给患者的正常生活、社交、工作等带来不利影响.此外,牙齿的缺失还将影响牙槽骨的功能,降低牙槽骨代谢能力,加快牙槽脊骨质的吸收及改建.人工种植牙因其美观性、稳定性、种植无需打磨邻牙等优势,逐渐成为缺牙修复的首选方式.口腔的...     

A new composite made of polyurethane and glass ceramic in a loaded implant model: a biomechanical and histological analysis

The biocompatibility and osseous integration of a new composite material made of polyurethane and a calcium silicophosphate ceramic was investigated in a loaded implant model in sheep and compared to that of commercially pure titanium. Six months after implantation, interfacial shear strength was higher between the titanium and bone than between the composite and bone. After 2 years, however, the shear strength was significantly higher in the composite group. Histologically, both implants were surrounded by bone and fibrous tissue and there were no signs of inflammation. Direct contact of bone on the composite surface increased significantly with time, whereas there was no time-dependent increase of bone contact on titanium. It can be concluded that the biocompatibility and osseous integration of the composite was very good in the loaded implant model used. It is therefore suggested that the new composite is a promising biomaterial for orthopaedic implants.     

A histomorphometric study on osteoconduction and osseointegration of titanium alloy with and without plasma-sprayed hydroxyapatite coating using back-scattered electron images

A quantitative evaluation, at the scanning electron microscopic (SEM) level, was made of the osteoconduction and osseointegration of Ti-6AI-4V implants with and without plasma-sprayed hydroxyapatite coatings (HACs). By employing the Chinese Coin implant model in the lateral femora cortices of canines, different biological properties between HA-coated and uncoated Ti-6AI-4V implants could be compared in one specimen. After 4, 6 and 12 weeks, the implants with surrounding bone were removed and assessed histologically in undecalcified sections under SEM. The osteoconductivity and the ability of osseointegration of implants were histomorphometrically analysed from back-scattered electron images (BEIs) and represented in terms of the new bone healing index (NBHI) and apposition index (AI), respectively. Throughout all implant periods, the HA-coated Ti-6AI-4V implants revealed higher NBHI than the uncoated ones, it appearing that the HA-coated Ti-6AI-4V implants revealed more osteoconductive than the Ti-6AI-4V was. For HA-coated implant, the evidence of direct bone-to-HAC contact was observed. However, at the bone/Ti-6AI-4V interface, there intervened a fibrous membrane without calcium content, indicating that the Ti-6AI-4V implant was not osseointegrated in the SEM field of view. The maximum value of AI was reached 6 weeks after implantation for HA-coated implant, implying that the HAC had a stimulating influence on bone apposition within 6 weeks of healing. The signs of partial dissolution of HACs within the remodelling canals were evident at the HAC-bone interface 12 weeks after implantation, accounting for the slight decrease in NBHI and the obvious decrease in AI for HAC implant.     

Effect of surface structure on biomechanical properties and osseointegration

The purpose of this study is to improve the bone-bonding ability between titanium implants and living bone through the control of geometric design and chemical compositions of an implant surface. We compared the tissue healing response and resulting implant stability for three surface designs by characterizing the histological and mechanical properties of the healing tissue around smooth-surfaced Ti–6Al–4V (SS), CP-Ti plasma-spray-coated (PSC), alkali- and heat-treated (AHT) implants. The implants were transversely inserted into a dog thighbone and evaluated at 4, 8, and 12 weeks. Histological examination indicated that initial matrix mineralization leading to osseointegration occurred more rapidly with the AHT implant. During the 4, 8, and 12 week healing periods, new bone on the surface of AHT implant showed denser growth than that on the SS and PSC implants. The more extensive tissue integration and more rapid matrix mineralization with the AHT implant were reflected in the mechanical test data, which demonstrated superior attachment strength and interfacial stiffness for the AHT implant after healing for 4, 8 and 12 weeks of healing because of the mechanical interlocking in the micrometer sized rough surface and the large bonding area between bone and implant caused by the nanosized porous surface structure. Histological and mechanical data demonstrate that with the appropriate surface design selection, bone bone-bonding ability can be improved and can induce acceleration of the healing response, thereby improving the potential for implant osseointegration.     

砧骨激励式人工中耳作动器的设计及实验

为治疗感音神经性听力损伤，设计的中耳植入式助听器，近年来已成为国内外研究的热点。提出一种砧骨激励式中耳植入助听装置，设计时综合考虑植入位置、空间、手术过程等，并对加工出的装置进行了相关实验。该装置采用压电式作动器，结构简单，作动器产生的力能够高效地传送至听骨链。在设计过程中使用有限单元法（FEM）对装置的共振频率和输出位移进行预估，仿真及实验结果说明该作动器具有良好的动态响应特性，谐波失真度小于1 %，在6.9 Vrms电压驱动下能够提供相当于鼓膜处90 dB SPL激励的效果，可以激励镫骨产生足够的位移以补偿听力损失，是一款有效的助听装置。     

Matrix generation within a macroporous non-degradable implant for osteochondral defects is not enhanced with partial enzymatic digestion of the surrounding tissue: evaluation in an in vivo rabbit model

Articular cartilage defects are a significant source of pain, have limited ability to heal, and can lead to the development of osteoarthritis. However, a surgical solution is not available. To tackle this clinical problem, non-degradable implants capable of carrying mechanical load immediately after implantation and for the duration of implantation, while integrating with the host tissue, may be viable option. But integration between articular cartilage and non-degradable implants is not well studied. Our objective was to assess the in vivo performance of a novel macroporous, nondegradable, polyvinyl alcohol construct. We hypothesized that matrix generation within the implant would be enhanced with partial digestion of the edges of articular cartilage. Our hypothesis was tested by randomizing an osteochondral defect created in the trochlea of 14 New Zealand white rabbits to treatment with: (i) collagenase or (ii) saline, prior to insertion of the implant. At 1 and 3-month post-operatively, the gross morphology and histologic appearance of the implants and the surrounding tissue were assessed. At 3 months, the mechanical properties of the implant were also quantified. Overall, the hydrogel implants performed favorably; at all time-points and in all groups the implants remained well fixed, did not cause inflammation or synovitis, and did not cause extensive damage to the opposing articular cartilage. Regardless of treatment with saline or collagenase, at 1 month post-operatively implants from both groups had a contiguous interface with adjacent cartilage and were populated with chondrocyte-like cells. At 3 months fibrous encapsulation of all implants was evident, there was no difference between area of aggrecan staining in the collagenase versus saline groups, and implant modulus was similar in both groups; leading us to reject our hypothesis. In summary, a porous PVA osteochondral implant remained well fixed in a short term in vivo osteochondral defect model; however, matrix generation within the implant was not enhanced with partial digestion of adjacent articular cartilage.     

Modulation of human dermal microvascular endothelial cell and human gingival fibroblast behavior by micropatterned silica coating surfaces for zirconia dental implant applications

Dental ceramic implants have shown superior esthetic behavior and the absence of induced allergic disorders when compared to titanium implants. Zirconia may become a potential candidate to be used as an alternative to titanium dental implants if surface modifications are introduced. In this work, bioactive micropatterned silica coatings were produced on zirconia substrates, using a combined methodology of sol–gel processing and soft lithography. The aim of the work was to compare the in vitro behavior of human gingival fibroblasts (HGFs) and human dermal microvascular endothelial cells (HDMECs) on three types of silica-coated zirconia surfaces: flat and micropatterned (with pillars and with parallel grooves). Our results showed that cells had a higher metabolic activity (HGF, HDMEC) and increased gene expression levels of fibroblast-specific protein-1 (FSP-1) and collagen type I (COL I) on surfaces with pillars. Nevertheless, parallel grooved surfaces were able to guide cell growth. Even capillary tube-like networks of HDMEC were oriented according to the surface geometry. Zirconia and silica with different topographies have shown to be blood compatible and silica coating reduced bacteria adhesion. All together, the results indicated that microstructured bioactive coating seems to be an efficient strategy to improve soft tissue integration on zirconia implants, protecting implants from peri-implant inflammation and improving long-term implant stabilization. This new approach of micropatterned silica coating on zirconia substrates can generate promising novel dental implants, with surfaces that provide physical cues to guide cells and enhance their behavior.     

Study of interface phenomena between bone and titanium and alumina surfaces in the case of monolithic and composite dental implants

The interface between mandibular bone and dental implants was examined with the in vivo dog model. Implant/bone interfaces were investigated for three types of materials: Ti–30 wt% Ta/Al2O3, titanium and Al2O3 using microscopy techniques covering a large magnification range: scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray analysis and Auger spectroscopy. During the interaction of the Al2O3 ceramic with bone, an interfacial layer about 15 m thick is formed. The same phenomenon was observed at the titanium bone interface, where the thickness of the layer was about 10 m. In all cases, interface layers were sharp with well-defined borders between bone tissue and implant materials. No calcification took place inside the interface layer. A chemical analysis performed on this layer shows the presence of titanium, calcium and phosphorus in the case of titanium implants, and aluminium, calcium and phosphorus in the case of alumina implants. A rapid decrease in metal composition with increasing distances from the implant surface is correlated to a slow increase in calcium and phosphorus in the direction of the bone. Direct contact between implant and bone was observed. No biocorrosive effects were detected at the Ti–30 wt% Ta/Al2O3 metal–ceramic interface.     

0—3型压电陶瓷—聚合物复合材料的制备与压电性

采用电陶瓷锆钛酸铅粉末掺入聚合物基聚偏二硫乙烯的方法，制备了柔性压电复合材料ＰＺＴ－ＰＶＤＦ。本文报导了这两种复合材料的制备工艺及其介电性和压电性，并讨论了在水听器方面的应用。