以奈/微米磁域為基礎所建構之磁珠操控技術

Abstract

本論文致力於觀測超順磁性磁珠於可變磁場下於各式奈/微米尺度下之單一磁域(Magnetic Single Domain)為基礎之軌道上的運動。磁珠之運動行為透過高倍率光學顯微鏡進行觀察。經由觀察結果，可以得知磁珠能吸附於本研究所製作之磁域軌道上，並且於大部分的情況下，磁珠內部之磁偶極會在改變外加磁場方向後傾向於順著磁場方向排列；由此，磁珠會吸附於單一磁域上區域性雜散磁場比較大的磁極上。然而，有時候磁珠會吸附於單一磁域區域性雜散磁場比較小的磁極上。針對此，我認為磁珠可能在切換磁場的過程中，因為磁珠於流體中受侷限之布朗運動而移動至靠近區域性雜散磁場比較小的磁極的區域，導致於磁場切換後磁珠會吸附於磁域上磁場強度較弱的磁極上。這些研究結果為未來開發用於生物微機電實驗室晶片之磁珠操控系統的核心技術。

This thesis aims to observe a superparamagnetic bead motion on the top of varies micro/nanoscale magnetic single-domain tracks under varies magnetic fields. The bead motion is observed by utilizing a high-magnification optical microscope. We find out that the bead can be trapped to the proposed magnetic-domain tracks. In most cases, after varying the applied magnetic field direction, the magnetic dipoles inside the bead will tend to align with the magnetic field direction, and thereby the bead will be trapped on one of the single-domain’s magnetic pole which has a larger local stray field. However, in some cases, the bead will be trapped to the single-domain’s magnetic pole with relatively small local stray field. According to this, we think that during the switching of the applied magnetic field direction, the bead randomly moved to a location near the small stray-field magnetic pole due to the confined Brownian motion of the bead. Therefore, after the applied magnetic field direction is switched, the bead is trapped on the small-stray magnetic pole. These experimental results are important core technologies to develop future magnetic bead manipulation for bio-MEMS lab-on-chip systems.