MRI: Development of Instrumentation for Direct Measurement of Forces Between a Colloidal Particle and a Surface

MRI：开发直接测量胶体颗粒与表面之间力的仪器

• 批准号: 9977459
• 负责人: Richard Dickinson
• 金额: $ 10.13万
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-09-01 至 2001-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9977459&HistoricalAwards=false
• 关键词: MRI; Development; Instrumentation; Direct; Measurement

CTS-9977459Dickinson, Richard BAbstractDevelopment of Instrumentation for Direct Measurement of Forces Between a Colloidal Particle and a Surface The interaction forces between particles and surfaces are of central importance to several current industry and biomedically relevant research projects at the University of Florida (UF). These include research efforts in the NSF Engineering Research Center for Particle Science and Technology (ERC) that focus on relating interparticle forces to dispersion and flocculation of particle suspensions. Of particular interest in this ERC is the role of polymer-induced colloidal forces such as steric and bridging interactions. The ERC is also investigating the role of particle surface properties in particle flocculation and deposition to surfaces in efforts to develop new and enhance existing particle separation processes. In other efforts at UF, the mechanism of bacterial attachment to biomaterial surfaces are being investigated in order to develop fundamental understanding the role of specific binding of cell surface macromolecule in the process of attachment. In other cell adhesion research, a collaborative seed project in the Biomedical Engineering Program funded by the Whitaker Foundation is investigating the physicochemical basis for specific cell adhesion to engineered biomaterial surfaces. Each of these current projects and similar envisioned projects would be greatly aided by the ability to directly measure the dynamic interaction forces between colloidal particle and a test surface. Furthermore, successful development of instrumentation to do so would have a broad impact on similar efforts elsewhere.An instrument that is capable of directly measuring static and dynamic forces between a single colloidal particle and a test surface. The instrument consists of a single-beam gradient laser trap (optical trap), which is used to micromanipulate the colloidal particle near the test surface. The particle position is precisely measured from the light scattered from an evanescent wave at the test surface. The force between the particle and the surface is measured from the deflection of the particle from the trap center. Scanning the trap position toward the surface allows measurement of the static interaction force as a function of separation distance. Furthermore, by analyzing the Brownian fluctuations of the particle position, more complex dynamic forces such asviscoelastic polymer-induced forces can be measured as a function of separation distance. To enhance this capability, a piezoelectric device will oscillate the optical trap at desired waveforms to allow analysis of the forces in response to an applied forcing function. The main novelty of this approach is to use the single beam gradient trap as a force transducer, analogous to a cantilever in atomic force microscopy, in combination with evanescent wave light scattering, which precisely measures the particle separation distance form the surface.A prototype of the instrument has been developed and has successfully demonstrated the proof-of-concept. The prototype is capable of simultaneously and accurately measuring static and dynamic forces vs. separation distance between an approximately one-micron colloidal particle and a transparent, optically flat surface. The sensitivity of the prototype ranges between 0.01 and ~5picoNewtons at ~ 1-3 nm spatial resolution. In terms of sensitivity, measurable particle sizes, and spatial resolution, this instrument has significant advantages over other available techniques for direct force measurement on colloidal particles. Based on the successful performance of the prototype, it is planned to develop a more sophisticated instrument for ultimate systematic use by multiple investigators in multidisciplinary research projects at UF. The proposed instrument will include a much more powerful trapping laser and a piezoelectric position device for more dynamic control on the position of the optical trap. Also, it will be capable of measuring backscattered light form the trapping laser, which will allow detection of submicroscopic particles in the trap and a means to calibrate the trap far from the surface. Cooled photomultiplier tubes will enhance the signal-to-noise ratio and provide more precise measurements. These features will greatly enhance the performance capabilities over the prototype.

直接测量胶体颗粒与表面间作用力的仪器研制颗粒与表面间的相互作用力对于佛罗里达大学（UF）当前的几个工业和生物医学相关研究项目至关重要。 其中包括NSF颗粒科学与技术工程研究中心（ERC）的研究工作，重点是将颗粒间力与颗粒悬浮液的分散和絮凝联系起来。 在ERC中特别感兴趣的是聚合物诱导的胶体力的作用，如空间和桥接相互作用。 ERC还在研究颗粒表面性质在颗粒絮凝和沉积到表面中的作用，以努力开发新的和增强现有的颗粒分离工艺。 在UF的其他努力中，正在研究细菌附着于生物材料表面的机制，以基本了解细胞表面大分子在附着过程中的特异性结合作用。 在其他细胞粘附研究中，惠特克基金会资助的生物医学工程项目中的一个合作种子项目正在研究特定细胞粘附到工程生物材料表面的物理化学基础。 直接测量胶体颗粒和测试表面之间的动态相互作用力的能力将极大地帮助这些当前项目和类似的设想项目。 此外，成功研制出这样做的仪器将对其他地方的类似努力产生广泛的影响。一种能够直接测量单个胶体颗粒与测试表面之间的静态和动态力的仪器。 该仪器由一个单光束梯度激光阱（光阱）组成，用于对测试表面附近的胶体颗粒进行显微操作。 颗粒位置是从测试表面处的倏逝波散射的光精确测量的。 粒子和表面之间的力是从粒子偏离陷阱中心来测量的。 朝向表面扫描陷阱位置允许测量作为分离距离的函数的静态相互作用力。 此外，通过分析颗粒位置的布朗波动，可以测量作为分离距离的函数的更复杂的动态力，如粘弹性聚合物诱导的力。 为了增强这种能力，压电器件将以期望的波形振荡光阱，以允许响应于所施加的强制函数来分析力。 该方法的主要新奇是使用单光束梯度阱作为力传感器，类似于原子力显微镜中的悬臂梁，结合倏逝波光散射，精确测量颗粒与表面的分离距离。该仪器的原型已经开发并成功地证明了概念验证。 该原型能够同时准确地测量静态和动态力与大约一微米的胶体颗粒和透明的光学平坦表面之间的分离距离。 原型的灵敏度范围为0.01和~ 5皮牛顿在~ 1-3 nm的空间分辨率。 在灵敏度，可测量的颗粒尺寸和空间分辨率方面，该仪器具有显着的优势，比其他现有的技术直接力测量胶体颗粒。原型的成功性能的基础上，计划开发一个更复杂的仪器，最终系统地使用多个研究人员在UF多学科研究项目。 所提出的仪器将包括一个更强大的捕获激光器和一个压电定位装置，用于更动态地控制光阱的位置。 此外，它将能够测量来自捕获激光器的反向散射光，这将允许检测陷阱中的亚微观颗粒，并提供一种远离表面校准陷阱的方法。 冷却的光电倍增管将提高信噪比，并提供更精确的测量。 这些功能将大大增强原型的性能。