在微流系統中利用介電泳力捕捉及分離微粒與細胞

Abstract

介電泳力可依據微粒或細胞柯莫氏因子的不同，將尺寸接近的微粒或細胞作選擇性的捕捉與分離。相關裝置為一直線微流道(底壁為玻璃，其他壁面為PDMS)，流道上壁建構有四個凹槽，凹槽區上下游兩側底壁上各建置一電極，以產生電場。依據介電泳力、流體拖曳力、重力和浮力平衡的結果，不同微粒會被推入凹槽被捕捉或是被流體帶住下游。本研究企圖釐清此設計的各項幾何參數及操作條件，以研發一項能有效分離類同大小但不同種類微粒的微流裝置。為了簡化問題，本文將就單一凹槽的設計進行研究。以聚苯乙烯粒子、肺腺癌細胞(CL1-0及CL1-5)與大腸癌細胞(Colo205)進行實驗，探討電場頻率(100kHz~10MHz)、流道高度(25μm、30μm、35μm)、凹槽寬度(35μm、45μm)和背景流體流速(20~130μl/h)等參數對微粒捕捉率的影響，統計出適當的操作範圍。經由實驗，本裝置亦被證明可用於捕捉懸浮於血液中的肺腺癌細胞。最後本文提出一項改良裝置並予以測試，其設計為凹槽與電極修改為與流道傾斜四十五度的結構，此一改良可將捕捉於凹槽內的微粒平順而有效地導流至系統中預設的目標位置。

A method was proposed for selective isolation and separation of particles/cells of similar sizes based on their different Clausius-Mossotti factors using dielectrophoresis and microfluidics in the literature. The associated device is a straight micro channel (glass for the bottom wall and PDMS for the rest walls) with four grooves on its ceiling for capturing particles, and two electrodes on both sides of the groove region for generating electric field. A particle may be carried downstream by the imposed fluid stream or pushed into the groove, depending on the local force balance between dielectrophoretic force, fluid drag, gravity and buoyancy. The present study aims to clarify the capturing efficiency of various particles/cells under different geometric designs and operating conditions, and hope to develop a microfluidic chip capable of separating different cells of similar size efficiently. In order to simplify the problem, a single groove design is employed in the present experiment. Capture rates for polystyrene particles, two lung cancer cells, CL1-0 and CL1-5 (more invasive), and one colorectal cancer cells, Colo205, were measured for different channel heights, groove widths, applied electric frequencies, and background volume flow rates. The device was also demonstrated of capturing CL1-0 cells from a mixture of CL1-0 and blood cells. A modified design of the device was also proposed and tested. The groove and the electrodes are orientated obliquely to the background flow in the modified design (but are perpendicular in the original design), such that the captured particles/cells in the groove can be guided smoothly and effectively to designed destination downstream.