不对称双面神粒子微探针流变检测仪

Colloidal particles have been extensively used as experimental probes for detection of complex fluid, soft matter, or condensed matter dynamics, including viscous and viscoelastic rheology response of fluids, with the benefits of reduced sample amount, much wider frequency range etc. The technique has been mainly focused on translational motion of spherical particles thanks to their abundance and very simple shapes. While rotational dynamics analysis that provides more information has been realized with anisotropic particles (e.g. rods, disks), the non-spherical shape brings in more complicated theoretical analysis, as well as the need of specific equipment in most cases. The optically asymmetric, yet geometrically symmetric and simple Janus particles, on the other hand, gracefully introduce detectable rotational dynamics to a spherical system. Preliminary data showed translational motions of Janus spheres, similar to conventional colloidal probes, were sensitive to fluid viscosity properties under thermal motions. These observations and theoretical simulation indicate Janus spheres are able to provide more insightful, consistent information of rheological properties of liquid mediums, dispersions or complex flows, as well as particle surface-liquid interactions, with less expensive instruments than currently available microrheology probes, yet there has been little devoted study on the topics given the young age of the "Janus" concept. Hence this project first proposes methods to extract, analyze 3-dimension translational and rotational Brownian dynamics of Janus spheres (e.g. thin metal film capped spheres) simultaneously, with the simple set-up of a fluorescence microscope equipped with a high speed CCD camera. We aim to develop a delicate, robust image analysis package, systemically examine particle dynamics behavior in a variety of viscous, viscoelastic fluids, and quantitatively determine thermal dynamics of Janus spheres. The second stage of this proposal is to extend the understanding to the effects of fluid mediums, particle surface properties (e.g. biomolecule coated Janus particles) on Janus particle dynamics, and especially to employ the result to quantify surface-liquid interactions. The research results are expected to further the understanding of effects of the surface properties and surrounding liquid mediums on the dynamics of Janus spheres. The ultimate goal is to advance applications of Janus particles as probes for microrheology of complex fluid mediums and biomolecular interactions.

胶体微粒子已广泛作为实验微探针检测黏性或黏弹性流体流变特性等。相比常规流变仪以胶体微粒子作为探针具有样品用量小、测量频率范围广，测量直接，可以还原流体原位真实性质等特点。常见微探针多为追踪球状微粒在介质中的布朗平动，近年来不对称微探针如棒状或盘状粒子的转动或平动加转动也被应用于各流体系统，比单纯平动信息更为丰富。然而这些粒子本身的复杂形状使得数据后处理和数理分析大为繁琐。双面神微球在保持几何形体简单的同时增加了不对称物化特性，其中光学不对称使得微球粒子转动示踪首次成为可能，由是简化示踪分析。本项目拟研制一简洁实用的双面神粒子微探针系统，开发微粒子3D平动－转动图像及数据分析平台，并在此基础上讨论不对称表面修饰对粒子热平动－转动影响，以期获得表面－流体相互作用量化信息。系统可最终用于更精确流变特性分析，以及实时分析反推生物大分子相互作用等与抗体筛选、结合特性、新药开发等相关的重要信息等。

项目以不对称结构为基础，面向关键科学问题，就简单形状的双面神Janus微球探针在流体中的热动力学行为进行了详细考察和探讨。研究内容主要集中在四个方面：（1）初步搭建了设置和确定了实验条件；（2）系统开发了对Janus探针的非圆形显微图像的示踪方法；（3）应用在牛顿型流体性质分析中；（4）应用在检测细微作用力中。在实验装置设计上，确定了选用PDMS薄圆环或刻蚀微槽结构以减少探针在z方向上的运动。不对称图形的图像分析和追踪取得了关键进展和一定突破，在图像分析上，示踪能够确定微米级的质心与三维方向性，用于分析探针的平动和转动，分辨率分别达到0.5像素（～50 nm）和10°以下。利用对Janus探针布朗运动的追踪确定了流体介质粘度，并通过与理论扩散系数比较确定了探针在z方向的相对位置。相关工作得到了同行的赞同性评价，被认为“will be an important resource for members of the asymmetric colloids community”。检测分子间力的实验结果处于整理中，数据表明在金半壳上修饰长链烃分子的Janus探针表现出与未修饰Janus探针不同的动力学，其转动速度相对加快，表现为追踪数据所得的扩散系数增大且不对称。此外在进行中的实验和撰写中的文章包括Janus微球的电动力学研究，以期为其组装成有特殊光、电、磁等效应的有序结构提供数据和依据，为扩展不对称结构的应用提供建议。项目主持人参加了相关领域有重要影响的国内外学术会议，在美国化学会胶体与界面科学分会（2014年）、中国化学会年会（2016年）上分别做了口头报告和墙报展示，增进学术交流、发展专业合作，与国内外一些研究所和大学建立了较为稳固的合作关系。在项目进行中注重工作质量与系统性，除发表两篇SCI论文外，申请了一项中国发明专利，协助培养硕士生两名，并获福建省自科基金拟立项。

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