Force controlled atomic force microscopy for biological specimen.

研究了聚酰亚胺悬臂梁用于力反馈的可行性。力反馈系统的稳定性主要得益于小Q因子和悬臂梁的低谐振频率。制备了聚酰亚胺悬臂梁，研究了其在真空条件下的力学特性，特别是Q因子。根据这些值，估计出力反馈系统所需的带宽。与具有相同特性的SiN悬臂梁相比，聚酰亚胺悬臂梁将频率要求降低到1/20，除了内部阻尼。通过数值模拟验证了系统的稳定性。带宽不足导致受力曲线振荡较大。为了提高Ti-6Al-4V的生物相容性，在O_2+H_2O气氛下，用ArF准分子激光在抛光后的基体（0.1 ~ 3.0μmR_<max>）上沉积了羟基磷灰石（HAp）薄膜。沉积过程中气体压力保持在13.3Pa （1×10^<-1>Torr）。衬底温度变化范围为500℃~ 5℃~ 60℃。采用x射线衍射（XRD）对HAp膜的晶体结构进行了表征。当温度低于500℃时，薄膜形成非晶态。在高于560℃的温度下，薄膜为结晶HAp和磷酸三钙（TCP）的混合相。利用原子力显微镜（AFM）观察了HAp膜的表面形貌。用拉伸试验机对薄膜进行了划伤试验和剥离试验，测定了薄膜的力学性能。结果表明：(1)在530℃左右获得HAp结晶；(2)在18N载荷下划伤实验中HAp膜明显脱落；(3)剥离实验中，表面粗糙度分别为0.1、1.0和3.0μmRmax时，HAp膜在基体上的粘附强度分别为2.3、5.4和10MPa；(4)体外评价HAp膜的生物相容性。不幸的是，为了研究生物标本，力控制原子力显微镜系统的稳定性是不够的。力控系统还需进一步改进。少

Feasibility of polyimide cantilever for force feedback method is studied. The stability of the force feedback system is mainly improved by small Q factor and the low resonant frequency of the cantilever. The polyimide cantilever is fabricated and investigated its mechanical feature, especially Q factor in a vacuum. Form these values the required bandwidth of the force feedback system is estimated. The polyimide cantilever reduces the frequency requirement to 1/20, compared with the SiN cantilever with same feature except for internal damping. The system stability is confirmed by numerical simulations. The bandwidth shortage results in large oscillation of the force curve. To increase biological compatibility of Ti-6Al-4V, thin film of hydroxyapatite (HAp) was deposited on the polished substrate(0.1〜3.0μmR_<max>) by ArF excimer laser in an atmosphere of O_2+H_2O.The gas pressure was kept at 13.3Pa (1×10^<-1>Torr) during the deposition. The substrate temperature was varied torn 500℃ to 5 … More 60℃. Crystal stractures of HAp film were evaluated by X-ray diffraction (XRD). At temperatures less than 500℃ the films resulted in amorphous. At temperatures greater than 560℃ the films had mixture phase of crystallized HAp and tricalcium phosphate (TCP). Surface morphology of HAp film was observed by atomic-force microscope (AFM). Mechanical properties of film were measured by the scratch test and the peeling off test by using tensile test machine. The following results were obtained : (1) The crystallized HAp was obtained at about 530℃, (2) In the scratch test, HAp film was clearly removed at the load of 18N, (3) In the peeling off test, the adhesive strength of HAp film on the substratewere about 2.3, 5.4 and 10MPa for the surface roughness 0.1, 1.0 and 3.0μmRmax, respectively and (4) Biocompatibility of HAp film was evaluated by in-vitro. Unfortunately, to investigate biological specimen the stability of the force control atomic force microscopy system is not sufficient. Farther improvement of the force control system is required. Less