STUDIES OF DIFFERENT VARIATIONS OF OPTICAL TWEEZERS WITH DIGITAL VIDEO MICROSCOPY CHEONG FOOK CHIONG (B. SCI (HONS.), NUS) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN SCIENCE DEPARTMENT OF PHYSICS NATIONAL UNIVERSITY OF SINGAPORE ACKNOWLEDGEMENT ACKNOWLEDGMENTS The author wishes extend his heartfelt appreciation for the guidance and supervision of his supervisor Associate Professor Sow Chorng Haur. His comments, suggestions and motivations over the years have been invaluable to my research and development as a student. He would also like to thank his family members and friends who have been very understanding and patient with him over the past few years. Especially, his parent, brother, and grandmother, they have always been there for him, watching him grow up from a curious boy to the inquisitive scientist he is today. Special acknowledgment goes to all his fellow friends of the Colloidal Lab Family, who have made graduate life more meaningful and wonderful. He would specially thank Ms Fong Yuet Lai in her constant moral support and contributions in the experiments. He is also very glad to have learnt writing IDL programming with her. He is happy to have Mr Zhu Yanwu for the numerous simulating discussions and suggestions on numerous topics in this thesis. He is in debt to Ms Lena Liu for her contribution to his understanding of colloidal science and atomic force microscope. And he is especially glad that she is such an encouraging and supportive friend whenever help is needed. The author would like to thank Dr Yu T. and A/Prof Shen ZeXiang for introducing the hotplate technique to grow metal oxide nanowires use in this thesis and for using optical travelator to align CuO nanowires. And he is grateful to Mr B. Vaghese for his help and suggestions during the study on focused laser writing of polymer. He would also like to thank Mr Lim K.Y. and his high school student for their contribution of using the vibrating membrane for dynamic optical trapping. Special ACKNOWLEDGEMENT thanks also goes to other members in the family, without them, research life in the lab will not be as colorful and unique. It is also important to thank all the supporting staff of the department. Especially, Ms E.T. Foo and friends in Engineering physics Laboratory for helping out in almost every aspect of the administrative works, like most of the equipment purchases and loans; Mr. Tan and all the technicians in physics workshops for helping out in the drilling of glass and technical support in the constructions of the experimental samples and chambers; Dr Andrew A. Bettiol, Prof F. Watt and friends in CIBA for their contributions to many great ideas and wonderful microlenses used in the thesis; Prof Andrew Wee and the friends in surface science laboratory and NUSNNI for offering assistances, advices, moral support and funding during the optical travelator project; A/Prof C.T. Lim and friends in bioengineering corridor for providing with invaluable advises and support in biological and cells manipulations with optical tweezers and nano-material studies; Ms Wang L.P for providing the micro-channels and optimistic approach to life ; A/Prof Chin W.S and her students for providing with some of the nano-materials used; A/Prof Ji W. and friends in the photonic laboratory for their assistant in non-linear optics studies; Prof Tang S.H. and his students in helping with the Raman and spectroscopy studies in some of the experiments; Prof Ong C.K. and friends in the CSMM for their constant support and listening to his endless enquires for help; He would also like to thank all the lab officers who have helped in the equipment loans and technical advises; A/Prof Edward Teo and the teaching staffs of physics department has also given him the opportunities to learn the art of teaching. Ms Sng W. L. and her officers in departmental office for the endless administrative support; And to all friends, teachers, classmates, students and helpers who have helped him to complete this thesis in one way or another, thank you all! TABLE OF CONTENT TABLE OF CONTENTS • Acknowledgement • List of publication • Figures Caption • Table of content Page 1. Introduction . 01 1.1. Introduction to optical tweezers . 01 1.2. Theory of optical tweezers 02 1.3. Single optical tweezers setup 06 1.4. Scope and review . 08 1.5. Summary 14 2. Multiple-beams Optical Tweezers . 18 2.1. Introduction to multiple-beams optical tweezers 18 2.2. Dual beams optical tweezers . 25 2.3. Multiple-Beams Optical Tweezers . 27 2.4. Experimental setup 29 2.5. Result and discussion 31 2.6. Integration tweezers array . 32 2.7. Summary 35 3. Optical Travelator 39 3.1. Introduction to line optical tweezers . 39 3.2. Experimental setup 41 3.3. Optical manipulation and sorting with optical travelator . 44 i TABLE OF CONTENT 3.4. Nanowires manipulation using optical travelator . 52 3.5. Optical travelator in biology . 56 3.6. Summary 57 4. Dynamic Optical Tweezers 61 4.1. Introduction to dynamic optical tweezers . 61 4.2. Dynamic optical tweezers experimental setup . 62 4.3. Theory of circular vibrating membrane 64 4.4. Results and discussions . 69 4.5. Optical induced rotation 71 4.6. Multiple dynamic optical tweezers . 77 4.7. Optical shuffle . 79 4.8. Summary 82 5. Defects Remediation using Optical Tweezers 85 5.1. Introduction to colloidal science . 83 5.2. Experimental setup 89 5.3. Colloidal interaction potential from pair-correlation function . 91 5.4. Calculation of colloidal crystal free energy using DLVO theorem . 95 5.5. Mediating colloidal crystal free energy using optical tweezers . 100 5.6. Colloidal crystal remediation with a scanning optical tweezers 103 5.7. Summary 106 6. Optical tweezers and Direct Focused laser writing 6.1. Introduction to focus laser writing 110 6.2. Experimental setup 111 6.3. Focus laser writing on nanomaterials . 113 6.4. Focus laser writing on polymer . 117 6.5. Applications . 120 ii TABLE OF CONTENT 6.6. Summary 125 7. Conclusion 130 • Appendix A: Principle behind optical trapping force in optical tweezers. iii SUMMARY SUMMARY In this thesis, different variations to optical tweezing and their different applications are presented. Optical tweezers coupled with digital video microscopy is a powerful tool to study the mechanics and dynamics of various mescopic systems. The objective of the thesis is to integrate optical microscopy with more complex optical designs to construct different variations of optical tweezers and study their plausible applications. The thesis starts with a brief introduction to the basic principles and construction of an optical tweezers. Then I introduced different techniques to construct multiple optical tweezers, line optical tweezers and dynamic optical tweezers. I have applied these various optical tweezers techniques to demonstrate various optical manipulation and optical sorting of colloidal particles. In addition, I have successfully demonstrated the use of dynamic optical tweezers system to two-dimensional colloidal crystals and have yielded new insights into the physics of soft-condense matter physics. iv LIST OF PUBLICATION LIST OF PUBLICATIONS INTERNATIONAL SCIENTIFIC JOURNALS 1. Cheong F.C. and Sow C.H., Defects Remediation using Optical Tweezers (in preparation) 2. Cheong F.C., Varghese B., Zhu Y.W., et al. WO3-x nanorods synthesized on a hotplate:a simple and versatile technique Journal of Physical Chemistry (Submitted) (2007) 3. Cheong FC, Varghese B, Sindhu S., et. al. , Direct Removal of SU-8 using focused laser writing, APPLIED PHYSICS A, Material Science and Process 87 (1): 71-76 APR (2007) 4. Cheong FC, Varghese B, Sindhu S., et. al., Manipulation and assembly of CuSx dendrites using optical tweezers, JOURNAL OF SOLID STATE PHENONMENA, 121123: 1371-1374 (2007) 5. Cheong F.C., Zhu Y.W., Varghese B., Lim C.T., Sow C.H., Direct Synthesis of Tungsten Oxide Nanowires on Microscope Cover Glass, ADVANCES IN SCIENCE AND TECHNOLOGY 51: 1-6 (2006) 6. Zhao Y. , Zhai W.C., Seah W. L., Cheong F.C, Sow C.H, Scanning Mirror on a vibrating Membrane for Dynamic Optical trapping APPLIED PHYSICS B: Laser and optics (2006) (Accepted) 7. Varghese B., Cheong FC, Sindhu S., et. al. , Size Selective Assembly of Colloidal Particles on Template by Directed Self Assembly Technique, LANGMUIR 22 (19): 82488252 SEP 12 2006 8. Hanafiah N. B. M., Renu R., Ajikumar P. K., Sindhu, S. Cheong F.C., et al. Amphiphilic Poly(p-phenylene)s for Self-organized Porous Blue Light-Emitting Thin Films, ADVANCED FUNCATIONAL MATERIALS 16 (18) , 2340-2345, NOV 2006 9. Cheong FC, Sow CH, A.T. Wee, et. al., Optical travelator: Transport and dynamic sorting of colloidal microshperes with an asymmetrical line optical tweezers, APPLIED PHYSICS B-LASERS AND OPTICS 83: 121-125 Feb 2006 10. Yu T, Sow CH, Gantimahapatruni A, Cheong FC, et al. Patterning and fusion of CuO nanorods with a focused laser beam, NANOTECHNOLOGY 16 (8): 1238-1244 AUG 2005 vi LIST OF PUBLICATION 11. Saurakhiya N, Zhu YW, Cheong FC, et al.Pulsed laser deposition-assisted patterning of aligned carbon nanotubes modified by focused laser beam for efficient field emission CARBON 43 (10): 2128-2133 AUG 2005 12. Bettiol AA, Sum TC, Cheong FC, et al.A progress review of proton beam writing applications in microphotonics, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 231: 364-371 Sp. Iss. SI APR 2005 13. Zhu YW, Yu T, Cheong FC, et al. Large-scale synthesis and field emission properties of vertically oriented CuO nanowire films NANOTECHNOLOGY 16 (1): 88-92 JAN 2005 14. Yu T, Cheong FC, Sow CH The manipulation and assembly of CuO nanorods with line optical tweezers NANOTECHNOLOGY 15 (12): 1732-1736 DEC 2004 15. Zhu YW, Cheong FC, Yu T, et al. Effects of CF4 plasma on the field emission properties of aligned multi-wall carbon nanotube films CARBON 43 (2): 395-400 2005 16. Tan BJY, Sow CH, Lim KY, Cheong FC, et al. Fabrication of a two-dimensional periodic non-close-packed array of polystyrene particles JOURNAL OF PHYSICAL CHEMISTRY B 108 (48): 18575-18579 DEC 2004 17. Sow CH, Bettiol AA, Lee YYG, Cheong FC, et al. Multiple-spot optical tweezers created with microlens arrays fabricated by proton beam writing APPLIED PHYSICS BLASERS AND OPTICS 78 (6): 705-709 APR 2004 18. Cheong FC, Lim KY, Sow CH, et al. Large area patterned arrays of aligned carbon nanotubes via laser trimming NANOTECHNOLOGY 14 (4): 433-437 APR 2003 19. Lim KY, Sow CH, Lin JY, Cheong FC et al. Laser pruning of carbon nanotubes as a route to static and movable structures ADVANCED MATERIALS 15 (4): 300-303 FEB 17 2003 INTERNATIONAL CONFERENCE PROCEEDINGS 20. F.C. Cheong and Sow C.H., Acoustic Controlled Dynamic Optical Tweezers, Proceeding in SPIE Symposium on Optics and Photonics, San Diego 2006 21. F.C. Cheong, et. al., Optical Travelator: Transport and Dynamic Sorting of Colloidal Microspheres with an Asymmetrical Line Optical Tweezers Proceeding in International Conference for Material and Advanced Technology (ICMAT) 2005 22. F.C. Cheong et.al, Direct Focused Fabrication of SU-8 microstructures, Proceeding in 2nd MRS Conference on Advanced Materiald 2006 vii LIST OF PUBLICATION 23. F.C. Cheong, et. al.,Manipulation and assembly of CuSx dendrites using optical tweezers Proceeding in st Nano conference in Beijing (ICMAT) 2005 24. F.C. Cheong, et. al., Multiple-spot optical tweezers created with microlens arrays, Proceeding in 1st MRS Conference on Advanced Material 2004 25. Yu T., F.C. Cheong, et. al., Manipulation and assembly of CuO nanorods with line optical tweezers , Proceeding in 1st MRS Conference on Advanced Material 2004 26. F.C. Cheong, et. al., Studies of Laser Modification and Fabrication of Patterned & Extended CNTs Array, Proceeding in International Conference for Material and Advanced Technology (ICMAT) 2003 BOOK CHAPTERS 27. C.H. Sow, K.Y. Lim, F.C. Cheong, N. Saurakhiya, et. al., Micro-Topiary – Laser Pruning of Carbon Nanotubes Arrays (Fabrication of static and movable D CNTs structures via Laser Trimming) Progress in Nanotechnology Research, Nova Science Publishers, 2005 viii Annex A Appendix A PRINCIPLE BEHIND OPTICAL FORCES IN OPTICAL TWEEZERS In general, light interaction with an object in a force laser beam can be divided into two components, optical gradient and optical scattering force, as mention in chapter of the thesis. For optical gradient force, it is mainly contributed from the electric field gradient from focusing the optical train to a tightly focused spot. For optical scattering, it can also be classed into two components. The first is the reflection and refraction at the surface of the particle, the second is the diffraction from the rearrangement of the wavefront after it interacts with the particle. While the radiation pattern due to reflection and refraction emanates from the particle in all isotropic in all directions and depends on the refractive index of the particle, the diffraction pattern is primarily in the forward direction of the propagating ray and depends only on the particle geometry. Two different regimes of theoretical approach can be distinguished. They are determined by the ratio of the incident light's wavelength λ to the diameter of the irradiated particle, a. In the ray optics regime (presented in Chapter of the thesis), the particle is very large compared to the wavelength (a >> λ), whereas in the Rayleigh regime the opposite is true (a [...]... Fig 5.6(a) Optical Micrograph of a colloidal crystal region before introduction of optical tweezers (b) Same region of the colloidal crystal during the introduction of a rotating optical tweezers and (c) Same region of the colloidal crystal after the introduction of the optical tweezers (d) Time evolution of the characteristic strain energy during and after the introduction of the optical tweezers Inset... development of this technique in order to obtain the rich scientific knowledge and opportunities unearthed by optical tweezers In this thesis, I will present different variations of optical tweezing and their different applications The main objective of the thesis is to demonstrate the integration of optical tweezers with more complex optical designs, at one or many points, to construct different variations of. .. variations of optical tweezers From a single spot optical tweezers, I expand the system to include two spots optical tweezers, multiple spots optical trapping and line optical tweezers For each variation of optical trapping, I have explored the possible applications for various colloidal systems Besides simple static optical tweezers of different variations, I have also investigated the option of using... setup of optical tweezers I have also introduced some of the works done on optical tweezers This chapter provided a brief review and scope of the different chapters I will be exploring in this thesis Constructions of different variations (single, dual, multiple, line and dynamic) optical tweezers and their applications will be discussed in detail in the following chapters With each new variation of optical. .. sphere with refractive index (a) larger than medium and (b) smaller than the medium [2] Fig 1.3 Schematic illustration for our optical tweezers set up used in this work Fig 2.1 (a) Schematic for a dual-beams optical tweezers setup (b) Photographs of the dual-beam optical tweezers setup (c) Optical micrograph of 1.2µm polystyrenes beads dispersed in aqueous medium (d) Optical micrograph of two optical tweezers. .. maxima The diameter of the microbeads is 5.1 µm Video clip of the trapping of the microbeads by this built-in optical tweezer array can be found at [18] Fig 3.1 (a) Schematic of a double line optical tweezers system and a sample cell that was coupled with electrodes for electrophoresis The inset shows the schematic of the intensity profile after a parallel beam with Gaussian intensity profile passes through... the influence of the line tweezers Scale bars = 15 µm Videoclips of the nanorods manipulation process can be found in website [27] Fig 3.7 Sequential optical micrographs of the manipulation of nanorods into a cross formation with the line tweezers Scale bars = 15 µm Videoclips of the nanorods manipulation process can be found in website [27] Fig 3.8(a-c) Sequential optical micrographs of manipulating... reflected off a multiple square array diffractive optical element (DOE) (b) Optical micrograph of multiple beams optical tweezers array trapping 1.58µm silica microspheres (c) Photographic images of multiple spots array becomes multiple lines array when the membrane is driven by a sound source of 150Hz (d) Optical micrograph of the resultant multiple-lines optical tweezers array aligning multiple pairs of. .. the period of 1s Video clips of shuffling of spheres assembly by the coupled vibrating membrane scanning mirror generated optical traps are available in ref [16] Fig 5.1(a) Schematic of the experimental setup used (b) Optical micrograph of SiO2 sphere trapped in a ring optical trap (c) Displacement time plot of the trapped particle trajectory Fig 5.2(a) Optical micrograph of an assembly of 1.58µm silica... Multiple-Beams Optical Tweezers Chapter 2 MULTIPLE-BEAMS OPTICAL TWEEZERS 2.1 INTRODUCTION TO MULTIPLE-BEAM OPTICAL TWEEZERS The technique of optical trapping, pioneered by Ashkin et al [1-3], is an active area of research A wide variety of experiments were made possible with the access and control that optical traps provide [4-7] In addition, rapid advances are also being made in the technical development of . STUDIES OF DIFFERENT VARIATIONS OF OPTICAL TWEEZERS WITH DIGITAL VIDEO MICROSCOPY CHEONG FOOK CHIONG (B. SCI (HONS.), NUS) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY. different variations of optical tweezers. From a single spot optical tweezers, I expand the system to include two spots optical tweezers, multiple spots optical trapping and line optical tweezers. . mescopic systems. The objective of the thesis is to integrate optical microscopy with more complex optical designs to construct different variations of optical tweezers and study their plausible