High and Low Frequency Scanning Acoustic Microscopes

这是一份购买高频(爆发式)和低频(脉冲式)扫描声学显微镜(SAM)的建议书。现在，使用频率高达2 GHz的扫描声学显微镜，以0.1微米的分辨率对材料进行微观机械测量成为可能。以所涉及的能量进行超声波扫描是一种值得注意的非破坏性技术；材料完好无损，不受这种分析技术的影响。然而，在材料的微观机械测量中，在分辨率和渗透深度之间存在权衡。频率越高，横向分辨率越大，但穿透深度是有限的，特别是对于那些具有高声阻抗值的材料。低频SAM特别适用于内部缺陷和界面不连续的成像。总而言之，SAM的一个明显优势是除了研究大多数材料的表面属性外，还能够研究内部和亚表面结构的属性，包括那些光学不透明的材料。这项技术的另一个优点，特别是对于那些涉及生物组织的研究，是必须使用液体偶联剂(通常是水)来将声波从声透镜传输到被研究的标本。“潮湿”的环境降低了在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SAM将是一个共享资源，一个由NIH资助的5名科学家组成的骨干已被确定为主要用户。建议的仪器在这些项目中的应用范围从细胞/组织水平的微观机械测量到实验环氧烷/多元醇复合材料的亚表面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出启动骨吸收的信号(P01AR46798)。研究人员将使用SAM来确定在施加不同程度的机械应变后骨骼的微观机械性能；这种仪器将为研究人员提供独特的机会，在单个骨板的水平上成像骨骼的微观机械性能。在另一项研究(P01 DE09696)中，将使用SAM来研究新合成的低收缩和低应力产生的树脂复合修复材料的断裂力学。SAM将与显微拉曼光谱相结合，在原位测定d/a界面(R01 DE12487)的分子结构和弹性性质。这些测量不仅将在相同的样品上完成，而且将在相同的界面小区域上完成。

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.