High and Low Frequency Scanning Acoustic Microscopes

这是购买高（突发模式）和低（脉冲模式）频率扫描声学显微镜（SAM）的建议。材料的微观机械测量现在可以在分辨率低至0.1微米的顺序使用扫描声学显微镜在频率高达2 GHz。超声扫描所涉及的能量是一种非破坏性的技术；材料完好无损，不受这种分析技术的影响。然而，在材料的微观力学测量中，在分辨率和穿透深度之间存在权衡。频率越高，横向分辨率越高，但穿透深度有限，特别是对于那些声阻抗值高的材料。低频SAM特别适用于内部缺陷和界面不连续的成像。综上所述，SAM的一个明显优势是除了研究大多数材料（包括那些光学不透明的材料）的表面性质外，还能够研究内部和地下结构的性质。这种技术的另一个优点，特别是对于那些涉及生物组织的研究，是必须使用液体耦合剂（通常是水）来传输声波，从声学透镜到被研究的样品。“潮湿”的环境减少了在那些对干燥敏感的生物标本中引入人工制品的可能性。高频和低频的SAM将是一个共享资源，由5名美国国立卫生研究院资助的科学家组成的骨干已被确定为主要用户。所提出的仪器在这些项目中的应用范围从细胞/组织水平的微力学测量到实验环氧烷/多元醇复合材料的表面下缺陷和界面耦合缺陷的表征。其中一位科学家感兴趣的是确定缺乏机械应变是否允许骨细胞发送启动骨吸收的信号（P01AR46798）。本研究者将使用SAM来测定在施加不同大小的机械应变后骨的微观力学性能；该仪器将为研究者提供独特的机会，在单个骨板水平上对骨的微力学特性进行成像。在一项单独的研究（P01 DE09696）中，SAM将用于研究新合成的低收缩低应力树脂复合修复材料的断裂力学。SAM将与微拉曼光谱相结合用于原位测定d/a界面（R01 DE12487）的分子结构和弹性性能。这些测量不仅可以在同一试样上完成，而且可以在界面的同一小区域上完成。

This is a proposal for the purchase of high (burst model) and low (pulse mode) frequency scanning acoustic microscopes (SAM). Micro- mechanical measurement of materials is now possible at resolutions down to the order of 0.1 mum using scanning acoustic microscopy at frequencies up to 2 GHz. Ultrasonic scanning at the energy involved is notably a non-destructive technique; materials are left intact and unaffected by this analytical technique. In the micro-mechanical measurement of materials there is a trade-off, however, between resolution and depth of penetration. The higher the frequency the greater the lateral resolution but, the depth of penetration is limited, especially for those materials with high acoustic impedance values. The low frequency SAM is particularly useful for imaging of internal defects and interface discontinuities. In summary, a distinct advantage of SAM is the ability to investigate the properties of internal and subsurface structures in addition to the surface properties of most materials, including those that are optically opaque. Another advantage of this technique, especially for those studies involving biological tissues is that a liquid couplant (usually water) must be used to transmit the acoustic waves, from the acoustic lens to the specimen being investigated. The "wet" environment reduces the potential for introducing artifacts in those biological specimens that are sensitive to desiccation. The high and low frequency SAM would be a shared resource and a cadre of 5 NIH-funded scientists have been identified as primary users. The application of the proposed instrumentation to these projects runs the gamut from micro- mechanical measurement at the cellular/tissue level to characterization of subsurface flaws and interfacial coupling defects in experimental oxirane/polyol composites. One of the scientists is interested in determining whether the lack of mechanical strain permits the osteocyte to send signals initiating bone resorption (P01AR46798). This investigator would use SAM to determine the micro-mechanical properties of bone after the applications of various magnitudes of mechanical strain; this instrumentation would provide the investigator the unique opportunity to image the micro-mechanical properties of the bone at the level of individual osteonic lamellae. In a separate study (P01 DE09696) SAM would be used to study the fracture mechanics of newly synthesized low-shrinking and low-stressing producing resin composite restorative materials. SAM would be used in combination with micro- Raman spectroscopy to determine the molecular structure and elastic properties of the d/a interface in situ (R01 DE12487). These measurements will e completed not only on the same specimen but the same small region of the interface.