Bachelor’s thesis THAI NGUYEN UNIVERSITY UNIVERSITY OF AGRICULTURE AND FORESTRY DO XUAN BANG TOPIC TITLE: WELL CONSTRUCTION OF POLY (METHYL METHACRYLATE) (PMMA) - BASED MICROFUIDIC DEVICE USING CARBON DIOXIDE LASER PROCESSING BACHELOR THESIS Study Mode : Full-time Major : Environmental Science and Management Faculty : Internatinonal Training and Development Center Batch : 2010-2015 Thai Nguyen, 23/01/ 2015 Bachelor’s thesis THAI NGUYEN UNIVERSITY UNIVERSITY OF AGRICULTURE AND FORESTRY DO XUAN BANG TOPIC TITLE: WELL CONSTRUCTION OF POLY (METHYL METHACRYLATE) (PMMA) - BASED MICROFUIDIC DEVICE USING CARBON DIOXIDE LASER PROCESSING BACHELOR THESIS Study Mode : Full-time Major : Environmental Science and Management Faculty : Internatinonal Training and Development Center Batch : 2010-2015 Superviors : Prof Yuh-Chang Sun MSc Nguyen Huu Tho Thai Nguyen, 23/01/2015 Bachelor’s thesis DOCUMENTATION PAGE WITH ABSTRACT Thai Nguyen University of Agriculture and Forestry Degree Program Bachelor of Environmental Science and Management Student name Do Xuan Bang Atudent ID DTN1053180011 Thesis Title Well construction of Poly (Methyl methacrylate) (PMMA) – based microfluidic device using carbon dioxide laser processing Supervisors Prof Yuh-Chang Sun MSc Nguyen Huu Tho ABSTRACT This study introduce about the topic: Well construction of Poly (Methyl methacrylate) (PMMA) - Based microfluidic device using Carbon dioxide laser processing The study described a methodology of using a model of CO2 laser system to ablation in PMMA based on the effects of laser power and processing speed on the depth and width of microchannels manufactured from poly methyl methacrylate (PMMA) Our result was like expectation, the study using high-resolution optical microscope to inspect the microchip and then they showed and capture image of microchops clearly to the desktop of computer It is observed that the channel depth varies linearly with an increase in laser power at a particular speed For a prescribed laser power, the channel depth decreased with an increase in laser speed for all the grades of PMMA The channel width increased with an increase in laser power but decreased with an increase in speed This results shows about what CO2laser can be using for well construction of PMMA and the depth, width and aspect ratio of the microchannels depend on the laser power and cutting speed and the profile of the microchannels can be easily controlled by CO2 laser system Number of page 38 Date of submission 23/01/2015 i Bachelor’s thesis ACKNOWLEDGEMENTS To accomplish this thesis, I would like to say thank to my University: Thai Nguyen University of Agriculture and Forestry, the Faculty of Environmental Science and Management, the teachers in schools have to pass on to me the knowledge during the time I study there I deeply thank to my Supervior Prof Yuh- Chang Sun at Department of Biomedical Engineering and Environmental Science, Tsinghua University, Taiwan who helped me, guided and accepted me to this thesis Who really friendly and always care for his students Without his support, I would like to say thanks to Assoc MSc Nguyen Huu Tho for his enthusiasm in guiding and correcting my report writing I would like to thank to my lab mates, Ph.D leader Shih Tsung-Ting and others were enthusiastic to help me Although I still not remember your real name until now, as well as the limitations of our language All of you guys have shown me the friendliness and culture of your country And trying to teach the most basic one by one I felt really comfortable and with the help of you Thank you so much Next one, from the depth of my heart, I would love to say thank for my parents who always encourage me during the time I my thesis During the internship I was trying my best to complete the requirements of The internships, but by experience and knowledge is limited, my thesis inevitable shortcomings and defects I look forward to the teachers and students to contribute additional ideas for my thesis to be excellent Thank you very much! Thai Nguyen, Jan 15th 2015 Signature of Student Do Xuan Bang ii Bachelor’s thesis TABLE OF CONTENTS PART I INTRODUCTION 1.1 Research rationale 1.2 Research’s objectives 1.3 Research questions and hypothesis 1.4 Limitations 1.5 Definitions PART II LITERATURE REVIEW 2.1 Fabrication of microfluidic device 2.1.1 Microfluidic device 2.1.2 Microfluidic chip 2.2 Birth of Microfluidics: a bit of History 2.3 Application of microfluidic device 12 2.3.1 The Microfluidic technology has found many applications mainly 12 2.3.2 Pros and cons about microfluidic device compared with traditional ways 13 2.4 The common materials for microfluidic chip fabrication 13 2.4.1 Inorganic Materials 14 2.4.2 Elastomers and Plastics 15 2.4.3 Elastomers 16 2.4.4 Thermosets 16 2.4.5 Thermoplastics 18 2.4.6 Hydrogels 18 Bachelor’s thesis 2.4.7 Paper 19 2.5 Mechanism of CO2 laser processing in PMMA 21 2.6 Experiment design and setup 22 2.6.1 CO2laser system 22 2.6.2 Experimental determination of threshold fluence 23 2.6.3 PMMA channel depth 24 2.6.4 PMMA channel profile 25 2.6.5 Channel micromachining 26 PART III METHODS 27 3.1 Reagent and Materials 27 3.2 Apparatus and Instrumentation 27 3.3 Methods 27 3.3.1 Draw microchannels on software for PMMA using AutoCAD 27 3.3.2 Setting and control for CO2 laser on AutoCAD 28 3.3.3 Control of CO2 Laser machine 29 3.3.4 Inspection of the channel 30 3.3.5 Using Power Image Analysis (PIA) systems for analyzing microchannels 31 PART IV RESULTS 33 4.1 Fabrication microchannels on PMMA 33 4.2 Effect of Speed and Power of CO2 laser on microchannels of PMMA 33 PART V DISCUSSION AND CONCLUSION 38 5.1 Discussion 38 5.2 Conslusion 39 REFERENCES 40 Bachelor’s thesis LIST OF FIGURE Figure 2.1 The first transistor 10 Figure 2.2 Glass microfluidic chip 11 Figure 2.3 Microfluidic chip made of PDMS on glass 11 Figure 2.4 Inorganic Materials 15 Figure 2.5 Elastomers 16 Figure 2.6 Thermosets 17 Figure 2.7 Hydrogels 19 Figure 2.8 Paper based microfluidic chips 20 Figure 2.9 Molecular’ structure of PMMA 21 Figure 2.10 Experiment system for laser micromachining of PMMA 22 Figure 2.11 Burn patterns in PMMA (the scale bar is 100 m) 23 Figure 2.12 Channel depth as a function of laser power at different scanning speeds 24 Figure 2.13 Comparisons of selected experimental channel profiles and their corresponding theoretical models 25 Figure 2.14 Experimental sample design for laser micromachining measurements 26 Figure 3.15 Schematic illustration of the channel 27 Figure 3.16 Setting for CO2 laser 28 Figure 3.17 PMMA substrate 29 Figure 3.18 Machining 29 Figure 3.19 High-resolution optical microscope 30 Figure 3.20 Breaking PMMA 30 Figure 3.21 Microchannel under Video input and measurement of PIA 16 30 Figure 3.22 SS-50 lens on High-resolution optical microscope 31 Figure 3.24 Size of Microchannel 32 Bachelor’s thesis Figure 4.25 Schematic diagram of the photothermal ablation process of CO2 laser on PMMA substrate 33 Figure 4.26 Microchips on PMMA 33 Figure 4.27 Effect of the laser power on depth 34 and width at a constant speed of 50% for PMMA 34 Figure 4.28 Effect of the laser beam speed in the depth and width of the microchannel at a laser power of 50% for PMMA 35 Figure 4.29 Photo of microchannels on PMMA took by PIA 36 with a constant power 50% and increases speed 36 Figure 4.30 Photo of microchannels on PMMA took by PIA with a constant speed 50% and increases power 37 Figure 4.31 Micrograph of a typical channel cross-section in PMMA at a laser power of 50% and speed of 25% 38 Bachelor’s thesis LIST OF ABBREVIATIONS PMMA : Poly methyl methacrylate PDMS : Poly dimethyl siloxane PIA : Power Image Analysis MMA : Methyl methacrylate HAZ : Heat affected zones SD : Standard deviations Bachelor’s thesis PART I INTRODUCTION 1.1 Research rationale The laser ablation mechanism is usually a combination of photochemical and photothermal processes, in which some chemical bonds of the substance are broken directly due to photon absorption while others are thermally broken by the released heat from those excited molecules that not break up photochemically A CO2 laser emits infrared radiation at a wavelength of 10.6 lm, which is not capable of directly breaking the chemical bonds, so that it is a totally photothermal mechanism for the CO2 laser ablation process, CO2 laser systems have been widely used for rapid production of microfluidic systems with polymers such as PMMA 1.2 Research’s objectives This study investigated a low cost direct writing laser ablation process to fabricate microchannel in PMMA using CO2 laser processing based on the effects of laser power and processing speed on the depth and width of microchannels manufactured from poly methyl methacrylate (PMMA) From the strong of position in low cost, fast speed and stable, it will open the door to development for well construction of Poly (Methyl Methacrylate) (PMMA)-based microfluidic device using CO2 laser processing 1.3 Research questions and hypothesis i) Will the possibility of using CO2 processing for fabricate microchannel in PMMA become real? ii) What is the effect of laser power and processing speed on the depth and width of microchannels from Poly methyl methacrylate (PMMA) for determining their percentage for setting CO2 laser processing? Bachelor’s thesis First step of method was used AutoCAD software (Figure 3.15) to draw a picture that used for control CO2 laser could be recognize and processing on PMMA This experimental have drawn totally 24 chips and each chip has three microchannels Then been classified the chips to two groups (Figure 3.15), one group for setting the power of laser constant and one group for setting the speed of laser constant Next step was made the sign by different colors for each chip to distinction with others Draw a horizontal line on the mid of all chip where we going to broken all the chip later 3.3.2 Setting and control for CO2 laser on AutoCAD Figure 3.16 Setting for CO2 laser First step for print our picture based on CO2 laser was chose what type of laser In this experimental we have chosen EZLASER Driver (LES) Then to be set the Speed and Power for all the chips respective with their color (Figure 3.16) 28 Bachelor’s thesis First group on the top was set Speed as constant 50% and Power with first chip was 25% Every chip increased 5% power until 80% Then we set the Power as constant 50% for the other group and the Speed also set from 25% to 80% After that was set 90% Power and 4% Speed for horizontal line (red color) and for green line that used for divide the entire chip 3.3.3 Control of CO2 Laser machine Figure 3.17 PMMA substrate Figure 3.18 Machining Turn CO2 laser on, put down PMMA in CO2 laser (Figure 3.17) This study still used AutoCAD for start, press “start” on machine and then waiting for machine to finish the work (Figure 3.18) 29 Bachelor’s thesis 3.3.4 Inspection of the channel Figure 3.19 High-resolution Figure 3.20 Breaking PMMA ]optical microscope After CO2 Laser finish its work, taken out PMMA, clean machine and turn it off And then beaked the chip follow the channel, in half (Figure 3.20) and made the sign for each chip Figure 3.21 Microchannel under Video input and measurement of PIA 16 30 Bachelor’s thesis 3.3.5 Using Power Image Analysis (PIA) systems for analyzing microchannels To using high-resolution optical microscope to inspect the microchip, this experimental need to have a computer linking with optical microscope, it can show and capture image of microchops to the desktop of computer It can help us observe object and measure microchips It can control the step less magnification and select suitable magnification to observe object And it can show the pictures of microchannels clearly on computer (Figure 3.21) After us measuring all of microchip we saved them to make the data table and line chap (Figure 4.28, 4.29) Turn on microscope (Figure 3.19) and put the lens SS-50 under microscope Open PIA 16 and click Video Input and measurement (Figure 3.21) Save the picture of lens SS-50 in bmp file, open that file and click Analysis =>Auto set Image resolution By SS-50 rule => enter =>Analysis =>Set image resolution by point => chose point and set them as 1mm and saved it (Figure 3.22) These steps very important for PIA could be measuring for all the chips in next step Figure 3.22 SS-50 lens on High-resolution optical microscope 31 Bachelor’s thesis Put the chips under microscope (Figure 3.19) Using cross line to make sure the picture of microchannel was horizontal (Figure 3.23), save the picture in bmp file Then open there file click Analysis =>Horizontal Length (for get the Width of channel) and click Vertical Length (for get the Depth of channel) (Figure 3.24) And thensaved the files Figure 3.23 Using Cross-line to Figure 3.24 Size of Microchannel Microchannel was Horizontal Last step was taken all data in depth and width of all channels to made table and graph 32 Bachelor’s thesis PART IV RESULTS 4.1 Fabrication microchannels on PMMA A photothermal ablation process has happened during the CO2 laser cutting process When the laser beam with certain power and cutting speed focuses on the surface of PMMA substrate, the temperature of the irradiated spot will increase rapidly, inducing melting, decomposition and leaved a void in the work piece (Figure 4.25) Figure 4.25 Schematic diagram of the Figure 4.26 Microchips on PMMA photothermal ablation process of CO2 laser on PMMA substrate CO2 laser has rapid fabrication microchanels on PMMA substrate during some short minute Microchannels have structure as picture on AutoCAD (Figure 4.26) With clean machine system, there is no sign of dust on microchannels or bad smell for environment work 4.2 Effect of Speed and Power of CO2 laser on microchannels of PMMA In Figure 4.27 shows the relation ship between the laser power and depth as well as width of the channel at a scanning speed of 50% for PMMA It is observed that 33 Bachelor’s thesis keeping all other variables constant, there is a linear relationship between the laser power and the depth of the cut channels For PMMA, the depth changing increased from 0.0294 mm to 0.074967 mm when the laser power varied from 25% to 80%.At a constant speed, the width also increased from 0.231967mm to 0.4001 mm when the laser power was increased from 25% to 80% Similar relationships were obtained for all the grades of PMMA and for all the speeds The mechanism of CO2 laser micromachining is photothermal melting and evaporation due to a long wavelength of 10.6 of the laser It results in heat affected zones (HAZ) in solids, the molten zone in liquids and evaporated gas with high pressure in the laser working area The standard deviations (SD) in the measurement of the microchannel depth varied from and from 0.003522 to for the microchannel width The increase in SD in the measurement of width of the microchannels can be attributed to uncertainty of the exact location of the intersection of the microchannels profile of the channel surface and the horizontal plane Figure 4.27 Effect of the laser power on depth and width at a constant speed of 50% for PMMA 34 Bachelor’s thesis Figure 4.28 shows the dependence of the channel depth and width on the laser speed at a constant laser power of 50% for PMMA The beam speed varied from 25% to 80% It was observed that the channel depth decreased significantly from 0.1516mm to 0.024333mm while the width decreased marginally from 0.0412267mm to 0.02269mm The results suggest that the microchannel depths were inversely proportional to the beam speed Similar trends were observed for all the grades of PMMA studied At lower speeds, the laser has more time to focus on PMMA and then more melted material And when the laser beam moves with a higher speed, it spends shorter time at each spot, each microchannel, and consequently less heat is absorbed by the material, and then the result is microchannels shallower and narrower Figure 4.28 Effect of the laser beam speed in the depth and width of the microchannel at a laser power of 50% for PMMA 35 Bachelor’s thesis 25% 50% 80% Figure 4.29 Photo of microchannels on PMMA took by PIA with a constant power 50% and increases speed 36 Bachelor’s thesis 25% 50% 80% Figure 4.30 Photo of microchannels on PMMA took by PIA with a constant speed 50% and increases power Figure 4.29 shows more clearly about the photo of microchannels with a laser power with increases of speed in 25%, 50%, 80% for increases of width and depth Figure 4.30 shows the effects of laser power when we set a laser speed and increases power on increases of width and depth of microchanels 37 Bachelor’s thesis PART V DISCUSSION AND CONCLUSION 5.1 Discussion The feature size of the laser cut microchannel depends on the shape of the laser beam, its scanning speed, the laser power and the number of passes of the beam on the same channel Apart from this, the distance between the work piece surface and the working lens of the laser system also affects the channel profile In this investigation, the distance between the work piece and the laser beam was maintained constant throughout The cross-section of the channels depends on the thermal diffusivity of the workpiece material, on the speed of the heat diffusion in the material and on the intensity distribution within the laser beam In Figure 4.31 shows a cross-section profile of microchannel on PMMA at a laser power of 50% and speed of 25% Other grades of PMMA also have cross-section profile of microchannels Figure 4.31 Micrograph of a typical channel cross-section in PMMA at a laser power of 50% and speed of 25% 38 Bachelor’s thesis In Figure 4.29 and Figure 4.30 also show a problem that why the experimental need always set laser 25% to 80% If we set the laser power lower than 25% or laser speed higher than 80% the energy will be too low to engrave the channels, not clearly to analyzing and look at the channels But if we set the laser power higher 80% the chips will be penetrated This study has showed a problem that why it has used Cross-line (Figure 3.23) for make the photo of microchannels horizontal For measuring the chip, if the photo of channel was not horizontal or not chosen exactly point in mid of depth or the head and end the data of channel that got from channel will be wrong, they can give higher or lower then real data of channel 5.2 Conslusion In this study, CO2 laser system has rapid fabrication microchanels on PMMA substrate during some short minute, all of microchip have structure as photo that we was draw before, it shows that we can widely and quickly using CO2 laser system for fabricate microchannel in PMMA or for rapid others production of microfluidic systems with polymers such as PMMA The depth and width of microchip in PMMA has been depended on laser power and cutting speed They were increases with an increase in laser power, the depth increases linearly where the width increases marginally At a particular laser power, the depth decreases inversely with the laser beam speed And we has determining the percentage of setting CO2 laser processing on PMMA should be from 25% to 80% From the strong of position in low cost, fast speed and stable, it will open the door to development for well construction of Poly (Methyl Methacrylate) (PMMA)-based microfluidic device using CO2 laser processing 39 Bachelor’s thesis REFERENCES Becker, H and Gaertner, C (2007) Polymer Microfabrication Technologies for Microfluidic Systems Anal.Bioanal Chem, 390, pp 89–111 Choi, N W., Cabodi, M., Held, B., Gleghorn, J P., Bonassar, L J and Stroock, A D (2007) Microfluidic Scaffolds for Tissue Engineering.Nat Mater, 6, pp 908– 915 DeMello, J (2006) Control and detection of chemical reactions in microfluidic systems, Nature, 442, pp 394-402 Domachuk, P., Tsioris, K., Omenetto, F G and Kaplan, D L (2010) BioMicrofluidics: Biomaterials and Biomimetic Designs.Adv Mater, 22, pp 249– 260 Franke, H and Sterkenburgh, T (1994 ) Properties and Applications of Dielectric Materials Part (Brisbane, Australia, 3–8 July) (Piscataway, NJ: IEEE), pp 208–10 Ghaemmaghami, A M., Hancock, M J., Harrington, H., Kaji, H and Khademhosseini, A (2012) Biomimetic Tissues on a Chip for Drug Discovery Drug Discovery Today, 17, pp 173– 181 Griffith, L G 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UNIVERSITY UNIVERSITY OF AGRICULTURE AND FORESTRY DO XUAN BANG TOPIC TITLE: WELL CONSTRUCTION OF POLY (METHYL METHACRYLATE) (PMMA) - BASED MICROFUIDIC DEVICE USING CARBON DIOXIDE LASER PROCESSING BACHELOR... ID DTN1053180011 Thesis Title Well construction of Poly (Methyl methacrylate) (PMMA) – based microfluidic device using carbon dioxide laser processing Supervisors Prof Yuh-Chang Sun MSc Nguyen