由於實驗室研究方向將朝向捕捉分離生物樣品以及更小尺度的粒子分離系統，因而開始進行微流道相關的研究與製程。此研究之目的則是驗證學長所做之研究“光渦流陣列雷射光鉗系統於微流體中之分析與應用”之結果是否可行。由此開始進行微流道製成的學習摸索與及資料的蒐集，期間嘗試了許多種製程的方式分別有二氧化碳雷射光雕刻、黃光微影濕式蝕刻製程、黃光微影乾式蝕刻製程與黃光微影翻模製成，最後由於實驗上的限制與及各種製程上的極限，最後使用黃光微影翻模製成方能完成微流道的製程。接著進行微流道的測試與控制，期間將微流道許多的問題一一排除使致其流場可藉由壓力控制的方式將粒子的流線壓至所需要的位置。經由本論文之研究，　最後完成了實驗室於微流道製程的SOP流程，使實驗室於未來進行奈米等級的粒子捕捉時，可在製程上縮減許多不必要的測試時間。

Experimental study on the application of vortex array laser tweezers in microfluidic sorting system
Author : Guo-Rong Chen
Advisor : Shu-Chun Chu
College : National Cheng Kung University
SUMMARY
In this article, a new manufacturing process─microchannel made in lithography has been proposed. This manufacturing process is brand new in terms of microchannel manufacturing, and has the benefit of being moldable, making it more suitable for our laboratory.
This article concludes with discussion on the preliminary testing of the microchannel under operation. Then, we test its operation with vortex array optical tweezers. Finally, we discuss possibilities to improve the manufactured microchannel. 　
Key Word : Ince-Gaussian beam, Vortex Array laser beam, Optical tweezer, microchannel.
INTRODUCTION
In recent years, research of medical science and biotechnology has made microchannels a well-developed subject. Microchannels can be sorted into passive and active types. Passive microchannels implement specially designed channels which separate the particles, and are good for sorting large amounts of particles. However, the drawback of the passive microchannel is that the particles can only be sorted by size. The active microchannel can solve this problem. The most iconic sorting method is electric field and magnetic field sorting. These methods can sort through the difference in permittivity and permeability constants. Overall, optical tweezers have the traits of both the passive microchannel and the electric field variant, being able to sort particles of different permittivity and sizes.This particle uses the optical tweezers method, with the Ince-Gaussian beam vortex being used. The Ince-Gaussian beam is better for particle capturing than other optical tweezers due to the fact that it requires lower power for the same amount of capture force, which reduces the damage to the particle through heat.
MATERIALS AND METHODS
This article uses three converging channels to control the flowing direction of samples, which enables further sorting of samples. The manufacturing of the microchannel is by Soft Molding method. First, for the yellow light lithograph, the SU-8 photoresist and Silicon Wafer is used to make the Female Die. Next, PDMS (Polydimethylsiloxane) is used as the material for mold, and the product is finally packaged with Venoclysis Needle and Cutting Sheel. The resulting channel is 100um in both width and depth.
For the experiment, we use a concave resonator to excite an Ince-Gaussian laser beam. Next, the polarization beam-splitting prism splits the beam into two. One is directed into the Dove Prism to rotate the beam profile, arrange the Dove Prism to get a 90-degree rotation. The other beam is set in a distance so that it has a 90-degree phase difference with the former beam. Finally, the two beams converge into a single beam vortex, which is fed into the microchannel for particle separation.

Fig. 1 Orientation for Ince-Gaussian Beam Vortex Array 〖(U_VALB)〗_(4,4). (a) is a beam splitter, (b) Dove prism, (c) Polarization beam splitter, (d) & (e) Mirror, (f) Filter. Dove prism rotate π/4 let incident field rotate π/2 and use electric platform to control the distant let phase difference between two Ince-Gaussian Beam field π/2 then converge two Ince-Gaussian Beam field and obtain Ince-Gaussian Beam Vortex Array.

Fig. 2 Experimental set up. (a) 1064nm laser cavity, (b) Beam expander, (c) Ince-Gaussian Beam Vortex Array.
RESULTS AND DISCUSSION
During the experimental process, the experiment did not go on well due to the presence of bubbles in the channel, thus the convergence of the three cannot be precisely observed. Thus the primary problem to be solved in the future is the bubbles. This can be done by dipping the sample in DI-Water, then vacuuming the sample to sap out the bubbles.
The second problem that occurred is that the channel is too deep that during the observing and capturing process, not all passing particles can be caught and moved, causing unsuccessful separation. Thus the depth of the channel must be reduced to about 20um in order to observe and capture successfully.
Fig. 3 Ince-Gaussian Beam Vortex Array from CCD (a) 〖(U_VALB)〗_(4,4), (b) 〖(U_VALB)〗_(2,2), (c) 〖(U_VALB)〗_(0,0).

Fig. 4 10um particle under Ince-Gaussian Beam Vortex Array 〖(U_VALB)〗_(4,4) (red circle is a particle and yellow spot is a Vortex Array Beam Spot ).

Fig. 5 5um particle under Ince-Gaussian Beam Vortex Array 〖 U_VALB)〗_(4,4) (bule circle is a particle and yellow spot is a Vortex Array Beam Spot ).
CONCLUSION
A manufacturing process of the microchannels has been Crated that is “yellow light etching” to manufacture deep microchannels.
A manufacturing process of the microchannels has been built for the laboratory, and the flowing and moving via beam vortex of particles in the microchannels has been ovserved.
In the future, a passive microchannel can be made based on this prototype, increasing efficiency of separation. This can also be combined with nano-scaled manufacturing, paving the way to the assembly of a microchannel-optical tweezers system for the scanning near-field optical microscope (SNOM).

[1] N. Pamme, “Continuous flow separations in microfluidic devices,” Lab. Chip. 12, 1644 (2007).
[2] J. Seo, M. H. Lean, and A. Kole, “Membraneless microseparation by asymmetry in curvilinear laminar flows,” J. O. Chromatography A 1162, 126 (2007).
[3] 盧奕宇, “光渦流陣列雷射光鉗系統於微流體中之分析與應用”, 國立成功大學物理研究所碩士論文 (2013).
[4] M. Kerker, The Scattering of Light and other electromagnetic radiation (Academic, 1969).
[5] S.-C. Chu, C.-S. Yang, and K. Otsuka, “Vortex array laser beam generation from a Dove prism-embedded unbalanced Mach-Zehnder interferometer,” Optics Express 16, 19934 (2008).
[6] 郭峻甫, “以數值模擬探討光渦流陣列雷射光鉗系統之特性”, 國立成功大學物理研究所碩士論文 (2012).
[7] 黃鈞正,吳崇安,邱爾德,“光學鉗住技術之簡介”, 物理雙月刊, 第二十捲, 第五期, 477 (2000).
[8] 鍾玉堆,許源鏞,許世卿,劉張源,王鴻烈,溫家俊, 流體力學概論 (大揚出版社, 1994), Chap. 4.
[9] R. J. Yang , C. C. Chang , S. B. Huang, and G. B. Lee, “A new focusing model and switching approach for electrokinetic flow inside microchannels,” J. Micromech. Microeng. 15, 2141 (2005).
[10] S. B. Kim, S. Y. Yoon, H. J. Sung, and S. S. Kim, “Cross-Type Optical Particle Separation in a Microchannel,” Anal. Chem. 80(7), 2628-2630 (2008).
[11] 蕭心縈,“光窩流陣列雷射之產生及其於光鉗應用之探討”, 國立成功大學物理研究所碩士論文 (2010).
[12] C. M. Andreou, J. Georgiou, and Y. Pahitas, “Bio-Inspired Micro-Fluidic Angular-Rate Sensor for Vestibular Prostheses,” Sensors 14, 13173 (2014).