以光調變TiOPc阻抗來建構二維度光驅動液滴操控平台的研究與開發

Abstract

近年來由於人口成長與老齡化問題，家庭醫療檢測監測系統已經廣泛受到重視。過去醫學檢測無不依賴於集中在都會型的中大規模診所，其就醫之限制降低了老年人口的醫療意願；而研究型醫院之檢驗實驗室與設備，隨著人口老年化所增加的醫療人數，使得現有醫療設備增添不及、檢測時程更加冗長，對於急性症狀與持續性長期生理監測造成檢測上的阻礙。過去十年來，數位微流體領域的研究發展進步帶動了實驗室晶片概念的興起，增加了居家檢測的便利性，讓檢測儀器與流程由大型醫院走向居家醫療的一環。然而，實驗室晶片系統發展至今仍然有其限制性，例如：在微小結構中必須使其具備檢體的運輸、傳遞、分離，篩選、純化、檢測等功能，在傳統的數位微流體晶片的結構設計上是極為繁瑣複雜的製程。如何使得微小檢測晶片製程簡化、增加檢測效率與重複使用性，仍然是此領域中大家努力的方向。 在此篇研究論文中，從數位微流體的基礎理論─電濕潤現象延伸，並將光敏材料(Photosensitive material) TiOPc加入傳統EWOD (Electrowetting on Dielectric)結構設計作為光驅動檢測晶片之基底平台架構，使檢測平台之電極結構利用光照可以重複定義，用以改變傳統數位微流體晶片架構裡複雜的微流道結構與與操作電極之製程，並在光敏材料與介電層材料(Positive photoresist S1813) 間做阻抗匹配，選擇不同操作頻率使晶片可轉換在光電濕潤(Optoelectrowetting)與光鑷子(Optoelectronic tweezers) 兩種模式。利用兩種模式的配合應用照光區域使液滴能完成移動、混合，篩選純化；並藉由光敏材料對於光強反應之差異，設計表面濕潤梯度來建構液體自發性傳輸路徑。 最後我們選用膜厚度為3.5μm之TiOPc作光感層、膜厚度為1.2μm之正光阻S1813為介電層，搭配厚度30 nm之AF1601為疏水層，並在高度為1 mm的晶片腔體內灌入十二烷(C12H26)絕緣油，以極化後的純水3μl作為操縱液體。結果可得此體積液體隨著照光驅動之移動速率可達5mm/s ，可移動體積為10μl/s，並量化照度與電濕潤現象關係評估建構居家檢測用途之自主操縱光流體晶片的可行性。

In recent years, home medical detection monitoring system has gained the public’s attention due to population growth and aging. Traditional medical tests were mainly conducted in large-scale clinics located in urban areas. This geographic element reduced the elderly population’s willingness for the medical treatments. Those research hospitals with the test lab and equipment, along with the increase in the aging population become more crowded and obviously insufficient. This tendency worsens the situation and remains an obstacle because of lengthy testing schedule for the acute symptoms and persistent long-term physiological monitoring. In the past decades, the development and progress of digital microfluidics research in this field led to the rise of the concept of lab chip that increases the convenience of home testing and minimize the necessary instruments and equipment. Thus, the conducted testing and examination are gradually shifted from the large hospitals into home health part. However, the development of the laboratory Chip still faces several restrictions, such as the need to have a minute structure specimen transport, transfer, separation, screening, purification, detection. There still leaves room to be improved in this field on how to simplify the manufacturing process to make tiny test chip and how to increase detection efficiency and reusability. In this study, we fundamentally start from the basic theory of digital microfluidic, the electrowetting phenomena. The base structure of our device is built by inserting the photosensitive material TiOPc into the traditional structure of Electrowetting on Dielectric (EWOD). The photosensitive material comprehensively changes the view of controlling mechanism from presetting the microelectrode to optically tailor the influence of surface electrode. More specifically, the electrode in our platform can be both defined afterward and redefined dynamically due to its photosensitive properties and reversibility. This aspect improves the complex micro-channel structure in digital microfluidic device and manufacturing of operation electrodes. Meanwhile, the impedance matching of photosensitive and dielectric materials is considered in detail. It not only ensures the operation of device but promises to work diversely for two modes, optoelectrowetting and optoelectronic tweezers respectively by adopting specific operating frequency. The successful combination of the two modes can achieve transportation, merging, dilution and purification onto the droplet within the device. Moreover, the various responses to light intensity of different levels for photosensitive material are implemented to profile the surface of wettability gradient and construct the route for autonomous motion of droplet. Finally, we utilize the 3.5μm thickness of TiOPc as photosensitive layer, 1.2μm thickness of positive photoresist S1813 as dielectric layer, 30 nm thickness of Teflon as hydrophobic layer to complete the base structure. Our device is completely packaged by covering an upside ITO glass and injection of Dodecane (C12H26) as isolation oil. The experimental results show that the transportation speed of 3μl deionized water is up to 5 mm/s and the volume flow rate of the liquid is up to 10μl/s in our device. The identification of the relationship of light intensity and electrowetting phenomena gives an outlook to estimate the feasibility for construction of the optofluidic chip with potential autonomous manipulation of samples for home medical detection.