Collaborative Research: Active and Nonlinear Microrheology

提案编号：0730292/0730270主要出版商：Furst，Eric M./作者：托德，M.机构：特拉华州大学/加州大学圣巴巴拉分校合作研究：主动和非线性微观流变学过去十年已经看到了被动微观流变学技术的发展，其中胶体示踪颗粒的布朗运动与周围材料的线性粘弹性有关。微流变测量的显著优点包括：仅需要微升样品，提供扩展的频率范围，并具有探测空间流变变化的能力。出于这个原因，工业界对适应和采用微流变方法表现出极大的兴趣。长期以来，人们已经认识到，用于处理复杂流体的大多数工业流程涉及与线性流变学的显著偏离。然而，被动微观流变学本质上不能测量非线性流变特性。在这里，我们的目标是开发第一个微流变技术来测量非线性材料的性能。这项合作将开发实验技术（使用激光镊子和高速共聚焦显微镜来测量力和非平衡结构，因为胶体探针被驱动通过材料）以及理解和解释结果的理论基础。目前，所有的理论和实验都只集中在直接的探针浴相互作用，这在宏观流变学中没有作用，并出现在被动微观流变学的文物。为了建立非线性微观流变学作为材料表征的一般技术，必须理解和解决这些问题，并开发和验证用于解释结果的有根据的方法。在建立了这些问题的理论和实验框架后，主要研究人员预计将使用更复杂的技术（例如，涉及多个和各向异性探针）来更忠实地测量非线性体流变学以及法向应力测量。其学术价值在于提出了发展和完善非线性微观流变学的第一种技术，从而建立了一个全新的流变学领域。更广泛的影响是，微流变学的发展有望在将生产规模扩大到工业规模之前测量非线性特性。与宝洁公司的互动将通过合作和博士工业实习加速这些方法的转移。此外，PI将利用现有的NSF资助的外展计划，将本科生，代表性不足的少数民族和高中学生和教师纳入他们的研究工作，在这个经济和技术上重要的领域提供教育机会。

PROPOSAL NO.: 0730292/0730270PRINCIPAL INVESTIGATOR: Furst, Eric M./Squires, Todd M. INSTITUTION: University of Delaware/University of California-Santa Barbara COLLABORATIVE RESEARCH: ACTIVE AND NONLINEAR MICRORHEOLOGYThe past decade has seen the development of techniques in passive microrheology, where the Brownian motion of colloidal tracer particles is related to the linear viscoelastic properties of the surrounding material. Significantly benefits from microrheological measurements include: requiring mere microliters of sample, providing an extended range of frequencies, and having the ability to probe spatial rheological variation. For this reason, industry has shown significant interest in adapting and adopting microrheological approaches. It has long been appreciated that most industrial flows for processing complex fluids involve significant departures from linear rheology. However, passive microrheology is by nature incapable of measuring nonlinear rheological properties. Here, the goal is to develop the first microrheological techniques to measure nonlinear material properties. The collaborative effort will develop both experimental techniques (the use of laser tweezers and high speed confocal microscopy to measure the force and non-equilibrium structure as a colloidal probe is driven through a material) as well as the theoretical basis to understand and interpret the results. Currently, all theory and experiments have focused exclusively on direct probe-bath interactions, which play no role in macro-rheology and appear as artifacts in passive microrheology. To establish nonlinear microrheology as a general technique for material characterization, these issues must be understood and addressed, and well-founded methods for interpreting the results must be developed and validated. Having established the theoretical and experimental framework for these issues, the Principle Investigators anticipate using more sophisticated techniques (e.g. involving multiple and anisotropic probes) for more faithful measurements of nonlinear bulk rheology as well as normal stress measurements. The intellectual merit is in proposing to develop and refine the first techniques for nonlinear microrheology, thus establishing an entirely new area of rheology. Broader impact is the development of microrheology promises to measure nonlinear properties before scaling up production to industrial scale. Interactions with Procter and Gamble will speed transfer of these methods, both through collaboration and PhD industrial internships. Additionally, the PIs will leverage existing NSF-funded outreach programs to incorporate undergraduates, under-represented minorities and high-school students and teachers into their research efforts, providing educational opportunities in this economically and technically important field.