臺灣博碩士論文加值系統

過去數十年來，微流體技術及裝置已被廣泛應用於不同的研究及工程領域。相較於傳統裝置，微流體裝置具有反應時間短、所需試劑少及耗能較少等優點。流量控制是微流體裝置的其中一項重要功能，且在同時處理多樣流體之裝置中尤其重要。本研究提出了兩種不同的微型致動器設計與其對應之多入口型微流體噴頭，並藉由致動器的作動來控制噴頭中兩側流體之流量，以改變噴頭出口處流體的組成比例。本研究所提出的第一項設計為形狀記憶合金致動器，形狀記憶合金在通電加熱後，可使致動器向前推進，進而擠壓流道壁面，而達到流量控制的效果。第二項設計則為氣動致動器，其可藉由增加氣室內壓力使其中薄膜產生變形，擠壓流道壁面，進而改變流體的流量。首先，本研究針對兩種致動器的反應時間及最大可作動位移進行了探討。隨後在致動器的流量控制效能的部分，則由一系列微粒子影像測速實驗進行詳盡的量測，並以兩側流量間的比例來表示其效能。在本研究中，兩種致動器所達到的最大兩側流量比例分別為1.74及1.22。為了未來能夠將此流量控制的概念應用於生物列印系統中，本研究亦做了許多額外的測試及展示。首先，本研究藉由額外的微粒子影像測速實驗來證實此多入口型噴頭設計有助於減少中央流體所受之平均剪應力。隨後，本研究也使用此噴頭實際進行水膠結構的列印，並展示了多種立體結構及分層結構。最後，本研究針對使用的水膠材料之生物相容性進行了探討。大鼠神經膠質瘤細胞被均勻種植於水膠結構之表面，經過二十四小時的培養後，附著於水膠表面的細胞仍具有極高的生存率，且細胞表面覆蓋率亦隨時間逐漸提升。根據這些結果顯示，本研究中所提出的列印材料將是為未來應用於生物3-D列印系統之良好候選。

Microfluidic devices pose serval advantages including less reaction time and less consumption in reagents and energy and have been employed into numerous research fields. Flow rate control is an important topic especially in microfluidic devices dealing with multiple materials. In this research, two new micro actuator designs were developed and integrated with corresponding multi-inlet microfluidic nozzle heads to achieve precise flow rate control over the composition of the extruded heterogeneous structures. The first actuator introduced is a shape-memory alloy actuator which impedes the channel wall and further change the flow rate when supplied with electric currents. The other actuator introduced is a PDMS pneumatic-based actuator which change the flow rate through deformation of the embedded thin film when applied with high pressure. Both actuators were quantified in terms of response time and maximum displacement achieved. Afterwards, a series of μPIV experiments were carried out to provide comprehensive investigations on flow rate controllability of proposed actuators in terms of flow rate ratio. In this research, maximum flow rate ratios of 1.74 and 1.22 were achieved. An additional μPIV experiment was performed as a proof of concept that the proposed multi-inlet nozzle is able to reduce shear stress induced to the central flow. Several hydrogel structures were printed and demonstrated using a remodeled bioprinter with multiple-layer filaments. Moreover, rat glioma (C6) cells were uniformly seeded on the surface of the hydrogel to investigate the biocompatibility of the hydrogel substrate. After 24 hours of incubation, the attached cells remained viable and good cell coverage rate were observed, which indicated that the presented material is an ideal candidate for future applications in bioprinting systems.

中文摘要 I
ABSTRACT III
ACKNOWLEDGEMENT V
Contents VI
List of Figures X
CHAPTER 1: INTRODUCTION 1
1.1 Literature review: Microfluidic devices and actuators 1
1.1.1 Backgrounds 1
1.1.2 Magnetic actuators 2
1.1.3 Piezoelectric actuators 4
1.1.4 Electric actuators 5
1.1.5 Thermal-mechanical actuators 7
1.1.6 Other types of actuators 9
1.2 Literature review: Bioprinting technologies 10
1.2.1 Backgrounds 11
1.2.2 Droplet-based bioprinting 12
1.2.3 Laser-assisted bioprinting 14
1.2.4 Extrusion-based bioprinting 15
1.3 Research motivation and objectives 17
CHAPTER 2: MATERIALS AND METHODS 19
2.1 Shape-memory alloy (SMA) actuator 19
2.1.1 Shape-memory alloy 19
2.1.2 Fabrication of SMA actuator 20
2.2 Pulse width modulation (PWM) based control system 23
2.2.1 Pulse width modulation (PWM) 23
2.2.2 Signal switching through potentiometer 25
2.2.3 Signal switching through serial monitor 28
2.3 Pneumatic-based actuator 30
2.4 Fabrication of multi-inlet microfluidic nozzle head 31
2.4.1 Replica molding process 32
2.4.2 Injection molding process 35
2.5 Flow rate quantification 39
2.5.1 Flow visualization and particle image velocimetry (PIV) 39
2.5.2 Micro-particle image velocimetry (μPIV) 42
2.5.3 Theoretical velocity distribution 44
2.5.4 Flow rate calculation 45
2.6 Concept of flow rate control through proposed actuators 49
2.7 Experiment configuration and analysis 50
2.7.1 Investigation of SMA actuator 50
2.7.2 Investigation of pneumatic-based actuator 52
2.7.3 μPIV experiment setups 54
2.7.4 μPIV analysis and flow rate quantification 56
2.7.5 Biomaterial printing 58
2.7.6 Cell growth on hydrogel 60
CHAPTER 3: RESULTS AND DISCUSSIONS 61
3.1 Performance of SMA actuator 61
3.1.1 PDMS wall displacement 61
3.1.2 Response time 62
3.1.3 Flow rate control through actuations 63
3.2 Performance of pneumatic-based actuator 68
3.2.1 Film deformation at different mixing ratios 69
3.2.2 Response time 71
3.2.3 Flow rate control through actuations 72
3.3 Discussions 76
3.4 Shear rate reduction through multi-inlet nozzle head 77
3.5 Hydrogel structure demonstrations 78
3.5.1 3-D structures with homogeneous material 78
3.5.2 2-D filament with heterogeneous materials 79
3.6 Cell growth on hydrogel 80
CHAPTER 4: CONCLUSIONS 83
CHAPTER 5: FUTURE WORK 85
REFERENCES 86

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