基于微/纳光纤的局域表面等离子微操控研究

Optical manipulation of microparticles using micro/nanofibers has already been investigated extensively in the fields of biology and medicine. However, it is very difficult to stable trapping and manipulation of nano size particles confined to intensity of evanescent field. To solve the problem, we can deposite gold nanoparticles on the surface of micro/nanofibers, and localized surface plasmon resonance of gold nanoparticles can be excited by the evanescent wave around the fibers, based on which two key applications of localized surface plasmon resonance in the field of micromanipulation will be investigated. Firstly, to obtain appropriate size condition, we study the optical field distributions of micro/nanofibers (different diameters) decorated with gold nanoparticles (different sizes) in the liquid, and calculate optical forces of microspheres placed on the surface of optical fibers and gold nanoparticles, respectively. Then, gold nanoparticles diluted are deposited on a specific position of the fiber. When microspheres delivered along the fiber come to the region of gold nanoparticles, the velocity of the spheres will be enhanced, based on which we can acquire the relationship between the distance of adjacent gold nanoparticles and enhanced velocity. Moreover, nano size particles can be stably trapped and transported by a fiber decorated with gold nanoparticles. Secondly, gold nanoparticles without being diluted are deposited on the designated position of the fiber, due to plasmonic photothermal effect, a steam bubbles will be formed on the fiber, and population trapping and manipulation of nanoparticles can be obtained. The implementation of this project will achieve the goal of decreasing the size of captured particles significantly and realizing nanometer capture.

用微/纳光纤表面的倏逝波操控微颗粒的方法，可广泛应用于生物医学等领域，但由于受倏逝场强度的限制，该方法很难稳定地捕获和操控纳米尺寸的颗粒。为了解决这一难题，本项目拟用微/纳光纤激发金纳米颗粒的局域表面等离子共振，研究其在微操控领域的两个主要应用：（1）研究不同尺寸金颗粒修饰的微/纳光纤（不同直径）在液体中的光场分布情况，计算微球分别置于光纤和金颗粒表面所受到的光力，获得合适的尺寸条件；在此基础上，将稀释后的金纳米颗粒沉积在光纤表面的特定位置，研究微球沿着光纤运动的过程中，经过金颗粒所在区域时的加速情况，分析得到相邻金颗粒的距离和微球速度增大倍数之间的关系；并用金颗粒修饰的光纤稳定地捕获和输送纳米尺寸的颗粒。（2）将无稀释的金颗粒直接沉积在微/纳光纤的指定位置，利用等离子光热效应产生的蒸汽气泡，实现纳米颗粒的群体捕获和操控。本项目的实施将达到显著地降低捕获粒子的尺寸，实现纳米捕获的目的。

微/纳光纤表面的倏逝波可激发金纳米颗粒的局域表面等离子共振，利用光场增强及光热效应，对颗粒进行稳定捕获和操控的研究是目前微纳光子学、生物医学、生命科学等学科领域的前沿热点。本项目通过模拟计算金纳米颗粒修饰的微/纳光纤表面的光场分布以及微颗粒在光纤及金颗粒表面所受到的光力情况，获得最佳的尺寸条件。以此为基础，利用200纳米的金球修饰的纳米光纤（500纳米），实现了沿光纤运动的聚苯乙烯微球的加速。此外，利用等离子共振光热效应所引起的热泳和热对流的共同作用，将直径为1微米的聚苯乙烯微球聚集在基地上。借助等离子光热效应所产生的热气泡，实现了对微颗粒的群体捕获和操控。我们提供的光学方法具有灵活简单、无损伤、成本低廉等特点，其结果具有一定的学术价值和应用前景。.项目资助公开发表SCI论文4篇（其中一篇已录用），在审SCI论文1篇，还有1篇论文正在整理中。