MRI-R2: Development of a Correlation Force Spectrometer

这个奖项是根据2009年美国复苏和再投资法案(公共法律111-5)资助的。对流体纳米尺度运动的更好理解对于我们对复杂流体和生物分子的理解是至关重要的。PI建议开发一种仪器，测量分子和流体在自然运动过程中的作用力，其能力超过所有当前的仪器。这台仪器将测量两个反平行悬臂的相关运动，这两个悬臂的自由端连接着原子力显微镜(AFM)尖端或胶体球。尖端之间的流体将耦合两个悬臂，从而相关的运动只对中间的流体敏感。与传统的原子力显微镜相比，这种反平行布置将大大降低悬臂梁的贡献。由于相关运动对单个悬臂梁上的电子、光学或机械干扰不敏感，因此对相关运动的测量导致信噪比的大幅增加。此外，即使是单个悬臂上的热噪声也不是相关信号的一部分，因此该仪器的噪声下限将低于现有单悬臂AFM技术的理论可能。该仪器将能够测量连接在两个悬臂之间的单个分子的机械性能，以及在高达数百kHz的频率下以纳米分辨率测量复杂流体的粘弹性属性。此外，机械概念的简单性为最终开发廉价而小巧的仪器提供了一条相对容易的途径。

0959228Ducker"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."An improved understanding of the nanometer-scale motion of fluids is central to the development of our understanding of complex fluids and biomolecules. The PI proposes to develop an instrument that measures the forces acting during the natural motion of molecules and fluids, with capabilities that exceed all current instruments. This instrument will measure the correlated motion of two antiparallel cantilevers that have atomic force microscope (AFM) tips or colloidal spheres attached to the free ends. The fluid between the tips will couple the two cantilevers such that the correlated motion is sensitive only to the intervening fluid. This antiparallel arrangement will greatly diminish the contribution of the cantilevers compared to conventional AFM. Measurement of the correlated motion results in a large increase in signal-to-noise ratio because the correlation is not sensitive to electronic, optical or mechanical disturbances on individual cantilevers. Moreover, even the thermal noise on the individual cantilever is not part of the correlation signal, so the instrument will have a lower noise floor than is theoretically possible for existing single cantilever AFM techniques. The instrument will be capable of measuring the mechanical properties of individual molecules tethered between the two cantilevers, as well as the viscoelastic properties of complex fluids with nanometer resolution at frequencies up to hundreds of kHz. Also, the simplicity of the mechanical concept provides a relatively easy path for ultimate development of an inexpensive and small instrument.