磁軸可再極化之高分子分散液晶聚合物微型裝置

Abstract

本研究將奈米磁性顆粒(MNP)摻雜在聚合物分散液晶(polymer dispersed liquid crystals, PDLC)中，開發了磁性微型裝置。本研究所提出的裝置可以使用直流磁場無線驅動進行運動。此外，我們更提出了裝置於操作過程使用微小磁場將磁軸再極化的方法。液晶液珠於高分子預聚合物進行聚合反應時析出，並隨機分布於聚合物基質中。形成的液晶液珠仍保有液晶的介晶相狀態，因此被液晶液珠的包覆的奈米磁性顆粒可以在液晶內移動。此磁軸再極化功能所需要的驅動磁場僅需30mT甚至更小的磁場。另一方面，裝置因為與奈米磁性顆粒的體積有巨大差異，裝置會先受到磁場驅動而奈米磁性顆粒則不會。此時透過亥姆霍茲線圈施加不同方向之均勻磁場驅動裝置轉向及移動。本研究也完成了PDLC-MNP微型裝置重要特性的驗證與探討，並成功於PDMS微流道中進行元件之無線操控。 本研究所使用了光敏感型高分子聚合物，可以透過照射紫外光使其聚合化。PDLC-MNP微型裝置可以使用微機電微影製程技術製作，因此裝置可以透過簡易的聚合相分離法，實現微機電製程技術批量生產的特性。本研究也完成了PDLC-MNP微型裝置在極化特性量測，可以得知再極化的完成度與時間及磁場大小皆呈正向關係。並且也微型裝置於微流道中的移動速度。

In this work, we propose a magnetic microdevice with the characteristic of tunable magnetic-axis. The proposed device was realized by patterning polymer-dispersed liquid crystal (PDLC) material doped with magnetic nanoparticles (MNP). A technique of in-situ realigning the direction of the device’s magnetic axis using small magnetic fields was also presented. The re-polarization can be achieved by applying the magnetic fields of less than 30 mT. The operation of the PDLC-MNP microdevices can be induced by using two pairs of Helmholtz Coils. The locomotion of the device, including translational motions, magnetic re-polarization, and rotational motion, was demonstrated in a PDMS microfluidic channel. Furthermore, the measured results also showed that rotation angle of the magnetic axis increases with the time of magnetization using a DC magnetic field. The velocities of the devices driven in the microfluidic channel with different concentrations of MNP were also measured.