磁性粒子操控之力學探討與於微奈米系統之應用

Abstract

磁性流體為一種人工製成之智慧型流體，主要結構為於特殊溶劑中加入多數體積質量相 等(直徑為微米尺度或者奈米尺度大小)的順磁性固體粒子，由於粒子密度較溶劑大，而 當粒子體積較大時(微米尺度)，其受布朗運動的影響較小，因此會產生沉澱的現象。由 於粒子為順磁性，利用此特性，可由不同型態之外加磁場以改變粒子在溶劑中的排列狀 態以及運動模式，藉此可以運用於先進生物技術或者微奈米之機械系統。在未來之應用 上，由於粒子在不同型態的外加磁場之下，可以展現出不同的運動型態，加上粒子為微 米或者奈米尺度，因此可應用於微流道之中，其中一項具體之應用為在微小的流道中加 上外加磁場，粒子因此受磁化作用而串接成鏈條狀，藉由外加磁場方向以及磁場大小之 改變，粒子串可以隨之改變其方向而達到一微流道中開關的作用。此外，若粒子受到外 加的旋轉磁場時，液體中的粒子串也回隨著磁場的方向改變而進行旋轉的運動型態，如 此可以達到微型混合器的目的，再者若施予粒子一個來回反覆的磁場，則粒子的運動型 態就會類似微生物的游動方式，產生一推力向前游動而可達到仿生的效果。 有鑑於對微磁性粒子操控技術研究之新穎創新性，於國外雖已有相當之先驅性研究成 果，然而於基礎理論模型(如磁性粒子間及與環境溶液間之作用力)，仍尚未有完整之 結論，且針對各類新型態操控應用方面(如生醫與微奈米系統)，更是尚有甚大之發展 空間，且就提案人所知，於國內尚無有相關之實驗研究，故而更應積極建立國內之相 關研究能量。因此本提案計畫預定於三年內完成磁性粒子之運動模式之操控分析，並 配合數值模擬來輔助實驗之精確度。首先將設置一套觀測微米尺度粒子之儀器設備以 及產生各型式之外加磁場架構以用以進行粒子操控，即可方便實驗進行並記錄磁性粒 子之運動軌跡情形加以分析。預定三年內之工作分配如下:於第一年主要進行觀測儀器 以及各種不同型式之外加磁場之儀器架設，蒐集相關之方程式，並著手於基本粒子之 運動理論分析研究，並進行粒子操控技術研究。第二年則利用第一年之理論分析及觀 測且紀錄粒子之簡單運動模式之實驗影片為基礎，來計算出微米粒子受磁力以及流體 力學之間交互影響的情形，以期可有效精確進行粒子串之操控。同時本年度之重點將 會以甚具挑戰性之微仿生游泳器為研究重點。第三年則將以進行創意導向型之應用研 究，研究重點將設計以更複雜之外加磁場型式來進行粒子串之操控，期待可設計出各 類型操控模式，有效應用於各類奈微米機電系統。

Magnetic fluids have been synthesized for technical applications since the early 1960s. They are colloidal suspensions of magnetic particles in carrier fluids such as water and oil. The development of magnetic fluid has created novel applications of similar studies with different driving forces. The advantages of flow controls for magnetic fluids by an external magnetic field have provided wide scopes of engineering applications in MEMS. In the meantime, practical uses in biomedicine have been achieved because of the great success in the development of stable ferrocolloids during the last decade. In a particular condition of fluid containing micro-sized particles, the particles could form chains under the influences of an external field. The particle chains can then be manipulated in various ways by properly adjusting the field distributions. These controllable particle chains possess great potentials for applications in nano-micro-systems, such as mixers, valves, pumps etc. In addition, if the motions of the chains can be well controlled similar to the vibrations of a fish body or fin, the chains can move just as a micro-swimmer. Nevertheless, to achieve above applications, well understandings to the formation of chains and the mechanisms acting on them are essential. The goals of the present proposed 3-year project are to study, both theoretically and experimentally, the manipulations of ferro-particles chains and their applications to nano-micro-systems. In the first year, the efforts will mainly be devoted on the understandings of chain formation and their mechanical properties as well as their motion under the influences of external fields. Once the particle chains can be well understood and manipulated, focus will be shifted to the design of effective micro-swimmers by the vibrations of particle chains in the second year. In addition, numerical simulations of the surrounding flow fields will also be conducted to give better understandings of the forces acting on the swimmers in the second year. The knowledge obtained from the previous two years would eventually be used in the final year for the developments of variant micro-components, which can be practically integrated and applied in a micro or nano system.