電液動驅動式低剪應力微型流式細胞儀

An Electrohydrodynamically Driven Actuator with Low Shear Stress for Micro Flow Cytometry

葉家和(Chia-He Yeh)

指導教授 ： 劉承賢

國立清華大學/工學院/奈米工程與微系統研究所/碩士(2009年)

摘要

流式細胞儀是現在臨床醫療、生物醫學研究上常用且重要的工具，唯其造價非常昂貴、體積龐大，結合微機電技術發展微型流式細胞儀將大幅降低其造價，屆時微型流式細胞儀即可普及並有利於各研究、學術單位。在更進一步的研究中，這幾年來又興起了幹細胞療法與相關進一步的研究，相較於一般細胞，幹細胞有更為脆弱、敏感的特性，流式細胞儀提供的高篩選速度雖相當便利，但對於相對較脆弱細胞、幹細胞或他種貴重、稀少細胞而言，大型傳統流式細胞儀可能對其具有刺激性或潛在的傷害性。
本研究提供一新型流式細胞技術，相較於一般傳統大型、或傳統微型流式細胞儀設計原理，我們的設計產生的剪應力明顯較低，若過大的剪應力作用在細胞膜上可能會造成細胞膜破損並傷害細胞，相關幹細胞的研究中也指出，某些特定幹細胞(ex: MSC, Mesenchymal Stem Cell)受剪應力作用後將會改變其分化趨勢與生長情況，可見剪應力太大將可能存在對篩選細胞的潛在影響，而長年來流式細胞技術中多採用流體聚焦效應(Hydrodynamic Focusing)，此原理中必定存在一較高的流速差來達到較佳的聚焦效果，本設計大幅降低了聚焦所需的流速差，從以往可能的流速比1：25（樣本流：鞘流）至1：70或更高比大幅降低至約1：1，流速差越小造成的剪應力也將越小，潛在的可能影響也將越小。 另外，我們也去除了長年來採用的外接注射幫浦與噴嘴(Nozzle)結構，除了增加方便性外，也避免了一些對細胞可能存在的潛在影響。我們提出一創新方法給相關研究一個新的思考與設計方向。

關鍵字

流式細胞儀 ； 流體聚焦效應 ； 電滲流 ； 剪應力

並列摘要

Flow cytometry is a standard and important tool for clinical medicine and research in biology. However, price of this machine is expensive and it also takes a lot of space. Thus, MEMS fabrication is used to lower down the price and be able to make flow cytometry affordable for labs and research institutes. Besides, recent advanced research about stem cell therapy indicates that some specific kind of stem cells are quite sensitive. Although flow cytometry is convenient for all cells in sorting, the high speed sorting also includes higher possible side stimulation or effects on both sensitive normal cells and stem cells.

This research topic proposes a novel flow cytometry design. Compared to other designs, we have lower shear stress. Shear stress implies on cell membrane may cause potential extra effects or even damages. Some research also indicates that some stem cells, such as MSC (Mesenchymal Stem Cell), is practically sensitive to shear stress and other mechanical loading. Under some shear stress stimulation, MSC may either change into another cell or change its physiology. Therefore, we also want to avoid this kind of influence while sorting cells. Various flow cytometries have been developed by taking advantages of hydrodynamic focusing as the main working principle to focus the cells in sample flow. Using conventional hydrodynamic focusing effect, a larger velocity ratio (or “flow rate ratio”), such as 1:25 (sample flow : sheath flow) to 1:70 or even higher, is required. In our design, we are able to lower the required velocity ratio down to near 1:1. This significantly removes the influence and potential damage from the shear stress for sorted cells. Besides, we get rid of the conventional used syringe pump and nozzle-shape flow channel. This makes chip work more convenient and also avoids the sudden changes in pressure and fluid velocity, which might potentially either damage or badly affect the sorted cells. Here we propose a novel design and new aspect of thinking in future corresponding research.

並列關鍵字

Flow cytometry ； Hydrodynamic focusing ； Electroosmosis flow ； Shear stress

參考文獻

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