Laser lithography was used to create novel patterns in thin diblock copolymer films. These patterns were characterized and an examination of their formation and growth was conducted. The patterns occurred only in diblock films, due to the interaction between thermal gradient induced Marangoni flow and the self assembly of the molecules. Growth of the patterns was found to be strongly dependent on absorbed power. The impact of film thickness on pattern growth was mainly due to the corresponding changes in sample reflectance, however a periodic patterning was observed suggesting that growth is also dependent on the amount of 'excess' material (over that required to form complete lamella) available. It was also shown that the pattern growth can occur independently of laser lithography and the Marangoni effect, though laser lithography was required to direct this growth. / Thesis / Master of Applied Science (MASc)

Laser lithography has been implemented in many ways to pattern polymeric materials. By using a tightly focused laser beam we can induce sharp thermal gradients, exceeding 1,500,000 °C/cm, onto the surface of a thin polymer film. The temperature dependence of the surface tension in such a thermal field gives rise to a flow of material away from the center of the beam focus driven by the Marangoni or thermocapillary effect. The evolution of a film irradiated by a focused laser can be, in a general sense, predicted by a presented hydrodynamic model, which is based on simple fluid mechanics. However, the details of the individual evolution profiles show a more complicated behaviour. It has been shown that this complex behaviour can be explained by considering the optical interference effects of the thin polymer coating. An optical feedback control routine has been developed to compensate for the interference effect by monitoring and maintaining a constant absorbed laser power. This ensures that the temperature gradient that drives the lithography process is consistent during operation. Additional studies involving high laser power effects, different material systems and other thin film phenomena have revealed an interesting assortment of novel behaviours. The extension of these behaviours to the lithography process lead towards the development of applications in microfabriation and microfluidic devices. / Thesis / Master of Applied Science (MASc)

Micromotors – untethered, motile, microscopic devices – are implemented in this dissertation for two applications in the field of assisted reproductive technology. First, as synthetic motor units for individual sperm cells, representing a novel approach to counteract sperm immotility (asthenozoospermia), which is one of the most prevalent causes of male infertility. Second, as synthetic carriers of fertilized oocytes (zygotes) towards the realization of non-invasive intrafallopian transfer, representing a novel alternative to the current keyhole surgery (laparoscopy) approach to achieve early embryo transfer after in vitro fertilization. In both applications, magnetically actuated micromotors are utilized to capture, transport, and deliver individual cells in a reproducible, controllable manner. In comparison with established in vitro fertilization routines, the crucial advantage of employing micromotors for the manipulation of gametes, i.e. sperm and (fertilized) oocytes, lies in the potential transfer of decisive steps of the fertilization process back to its natural environment – the fallopian tube of the female patient – taking advantage of the untethered, non-invasive motion and manipulation capabilities of magnetic micromotors. When sperm motility can be restored with magnetic micromotors, sperm can travel to the oocyte under external actuation and control, and the oocyte does not need to be explanted for in vitro fertilization. However, if in vitro fertilization was necessary, fertilized oocytes can be transferred back to the fallopian tube by micromotors in a non-invasive manner, to undergo early embryo development in the natural environment. These novel concepts of micromotor-assisted reproduction are presented and investigated in this thesis, and their potential is analyzed on the basis of proof-of-concept experiments.:1 Introduction 6 1.1 Background and Motivation 6 1.2 Objectives and Structure of this Dissertation 9 2 Fundamentals 11 2.1 Micromotors Definition and Concept 11 2.2 Micromotors for Biomedical Applications 13 2.3 Magnetic Micropropellers 15 2.3.1 Theory 15 2.3.2 Implementation 20 2.4 Microfabrication: Direct Laser Writing 21 2.5 Assisted Reproductive Technology 23 2.5.1 In vitro Fertilization and Intracytoplasmic Sperm Injection 24 2.5.2 Embryo Transfer and Zygote Intrafallopian Transfer 25 2.5.3 The Sperm Cell and the Oocyte 26 2.6 Towards Micromotor-Assisted Reproduction 28 3 Materials and Methods 30 3.1 Fabrication of Microfluidic Channel Platforms 30 3.1.1 Tailored Parafilm Channels 30 3.1.2 Polymer Channels Cast from Micromolds 31 3.1.3 Tubular Channels to Mimic In vivo Ducts 32 3.2 Fabrication of Magnetic Micropropellers 32 3.2.1 Direct Laser Writing of Polymeric Resin 33 3.2.1.1 Design and Programming 33 3.2.1.2 Exposure and Development 35 3.2.1.3 In Situ Direct Laser Writing 35 3.2.2 Critical Point Drying 35 3.2.3 Magnetic Metal Coatings 36 3.2.4 Surface Functionalization 37 3.3 Sample Characterization 38 3.3.1 Optical Microscopy 38 3.3.2 Scanning Electron Microscopy 38 3.4 Cell Culture and Analysis 39 3.4.1 Sperm Cells 39 3.4.2 Oocytes 39 3.4.3 In vitro Fertilization 41 3.4.4 Hypoosmotic Swelling Test 44 3.4.5 Cell Viability Assays 44 3.5 Magnetic Actuation 45 3.5.1 Modified Helmholtz Coil Setup 46 3.5.2 MiniMag Setup 47 3.5.3 Experimental Procedure 48 3.5.3.1 Micromotor Performance Evaluation 48 3.5.3.2 Cell Transport Experiments 49 3.5.3.3 Cell Transfer Experiments 50 4 Micromotor-assisted Sperm Delivery 51 4.1 Micromotor Design and Fabrication 51 4.2 Actuation and Propulsion Performance 53 4.3 Capture, Transport, and Release of Sperm 56 4.4 Delivery to the Oocyte 59 4.5 Sperm Viability and the Ability to Fertilize 61 5 Micromotor-assisted Zygote Transfer 68 5.1 Micromotor Design and Fabrication 68 5.2 Actuation and Propulsion Performance 70 5.3 Capture, Transport, and Release of Zygotes 76 5.4 Transfer between Separate Environments 80 5.5 Zygote Viability and Further Development 82 6 Conclusions and Prospects 85 Appendix 87 Bibliography 93 List of Figures and Tables 108 List of Abbreviations and Terms 109 Theses 111 Selbstständigkeitserklärung 112 Acknowledgments 113 List of Publications 115 Curriculum Vitae 116

Um estudo refinado dos filmes derivados do gel de pentóxido de vanádio foi realizado por meio de técnicas espectroscópicas e microscópicas visando compreender melhor as características deste material na escala microscópica. Foi demonstrado que o gel de pentóxido de vanádio é uma suspensão de nanopartículas anisotrópicas que se mantêm estáveis mesmo em altas concentrações. As propriedades estruturais e espectroscópicas destas nanopartículas foram revistas e discutidas no estado da arte. Em paralelo foi possível investigar fenômenos como a transição de fase induzida por laser e desenvolver aplicações tecnológicas em áreas como litografia e sensoriamento de gases. Ficou destacada nesta tese o grande potencial de investigação da microscopia Raman confocal na área de nanomateriais. / A refined study of films derived from vanadium pentoxide gel was carried out based on spectroscopic and microscopic techniques, aiming a better understanding of this material on a microscopic scale. It was demonstrated that the vanadium pentoxide gel consists of a suspension of anisotropic nanoparticles which remains stable even at high concentrations. The structural and spectroscopic properties of such nanoparticles were reviewed and discussed, providing new insights at the state of the art. It was also investigated the occurrence of some relevant phenomena, such as the laser induced phase transition, and to develop new technological applications in areas such as gas sensing and lithography. The collection of results described in thesis highlighted a great research potential of confocal Raman microscopy, in the field of nanomaterials.

In this thesis, theoretical investigation of nickel-like tin plasma is presented. X-ray production in a plasma medium produced by a laser beam is reviewed. Applications mostly, lithography are discussed. Two different schemes for x-ray lasing, namely, quasi-steady state and transient collisional excitation are explained and compared. The computer codes that are used for plasma, especially for laser produced plasma and x-ray laser including hydrodynamic codes, ray-trace codes and collisional radiative codes are discussed. The code used in this work, EHYBRID, is considered in more detail. An experimental setup which can allow x-ray lasing is designed for different plasma and laser parameters are analyzed by means of EHYBRID code. Results are briefly discussed and as a future work the realization of the related experiment is mentioned.

Thesis(MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The SQUID-NMR technique has been increasingly recommended by many researchers as holding a lot of potential, and it is believed it will become an invaluable tool for non-destructive evaluation in the future. Most of its potential is yet to be exploited. Non-destructive quality control of food products is one of the applications where such a system is being tried. Much of the progress that has been made in improving such a system to the present degree of user friendliness and cost effectiveness shows that, with more effort, it would be possible to implement the technology for on-line sorting, and possibly to reduce it down to hand-held devices. The goal was to investigate the feasibility of the internal fruit quality measurements using the NMR technique, and to develop a SQUID system suitable for SQUID-NMR application, intended for a later integration in a full SQUID-NMR system. A working dc SQUID was manufactured on an YBCO (Y Ba2Cu3O7􀀀 ) thin film deposited on a 10 mm x 10 mm MgO substrate. The SQUID was made of microbridge Josephson junctions, patterned by using the double resist laser lithography method, implemented during the course of this manufacturing process. The test of the SQUID showed a non-hysteretic current-voltage characteristic. Under the action of bringing a magnet closer to the SQUID under test, and then retracting it, the modulation of the I-V curve was observed. The critical current of the SQUID was 20 A and the resistance was 5.5 A series of experiments were performed on destructive measurements of the sugar content in table grapes using NMR, in order to evaluate the feasibility of this technique. The total sugars(TSS) measurements of the same samples were carried out by refractometry, chosen as a conventional method for validation. The NMR measurements were evaluated to be 5.4% precise and have an accuracy of 9.3% relative to the refractometry measurements. A further series of experiments were carried out on a high-Tc SQUID-NMR system. A high correlation coefficient (0.85) of the increasing values of the T1 and T2 relaxation times to the decreasing concentration of sugar (sucrose) in water was obtained. Non-destructive measurements T1 and T2 in table grapes suggested a possible prediction of sugar content in table grapes from the values of T1 or T2. This technique also presented many advantages compared to the conventional high field NMR technique, such as the fast measurements that do not require spectral processing, the ease of sample preparation, and its non-destructive nature. / AFRIKAANSE OPSOMMING: Die SQUID-NMR tegniek word al hoe meer aanbeveel deur navorsers oor die groot potensiaal, en dit beloof om in die toekoms van onskatbare waarde te wees in nie vernietigende evaluering. Die potensiaal moet grotendeels nog ontgin word, en die nie vernietigende kwaliteitsbeheer van voedselprodukte is een van die toepassings wat hier getoets word. Die vooruitgang tot dusver om die stelsel te verbeter wat die gebruikersvriendelikheid en koste-effektiwiteit betref, toon dat met effens meer moeite dit moontlik sal wees om die tegnologie aan te pas vir lynsortering van vrugte, en om dit dalk ook as handtoestel beskikbaar te stel. Die vooruitgang tot dusver om die stelsel te verbeter wat die gebruikersvriendelikheid en koste-effektiwiteit betref, toon dat met effens meer moeite dit moontlik sal wees om die tegnologie aan te pas vir lynsortering van vrugte, en om dit dalk ook as handtoestel beskikbaar te stel. Die doel is om die uitvoerbaarheid van interne vrugtekwaliteit metings deur hierdie tegniek te ondersoek en om ’n SQUID stelsel te ontwikkel wat gepas is vir SQUIDNMR toepassing, met die doel om dit later in ’n volledige SQUID-NMR stelsel te kan integreer. ’n Werkende GS-SQUID is vervaardig op ’n YBCO dunfilm wat op ’n 10 mm x 10 mm MgO substraat gedeponeer is. Die SQUID is van mikro-brug Josephson aansluitings/ voegvlakke, waarop in die loop van die vervaardigingsproses ’n patroon m et dubbelweerstand laser litografie neergelê is. Toets van die SQUID het ’n niehisterese stroom-spanning as kenmerkend getoon. Die nader bring en terugtrekking van ’n magneet het gelei tot waarneming van die modulasie van die I-V kurwe. Die kritieke stroom van die SQUID was 20 A en die weerstand was 5.5 ohm. ’n Reeks eksperimente is uitgevoer oor vernietigende metings van die suikerinhoud van tafeldruiwe met gebruik van NMR, om die gangbaarheid van hierdie tegniek te evalueer. Totale suikers (TSS) metings van dieselfde monsters is uitgevoer deur refraktometrie, wat gekies is as gebruiklike metode vir geldigheidsbepaling. Die NMR metings is as 5.4% presies/noukeurig evalueer, en met ’n akkuraatheid van 9.3% teenoor die refraktometrie metingsyfers. ’n Verdere reeks eksperimente is uitgevoer op ’n hoë-Tc SQID-NMR stelsel. ’n Hoë korrelasiekoëffisiënt van 0.85 van die toenemende waardes van T1 en T2 ontspantye teenoor die afname in konsentrasie van sukrose in water is waargeneem. Nie-vernietigende metings van T1 eb T2 in tafeldruiwe het gelei tot die moontlikheid van gebruik van hierdie tegniek om suikerinhoud van tafeldruiwe te voorspel. Die tegniek het ook baie voordele getoon in teenstelling met die gebruiklike hoëveld NMR tegniek, onder andere dat hierdie metings vinniger is, nie verdere verwerking van die spektrum benodig nie, die maklike voorbereiding van die monsters en die nie-vernietigende aard van die proses.

Um estudo refinado dos filmes derivados do gel de pentóxido de vanádio foi realizado por meio de técnicas espectroscópicas e microscópicas visando compreender melhor as características deste material na escala microscópica. Foi demonstrado que o gel de pentóxido de vanádio é uma suspensão de nanopartículas anisotrópicas que se mantêm estáveis mesmo em altas concentrações. As propriedades estruturais e espectroscópicas destas nanopartículas foram revistas e discutidas no estado da arte. Em paralelo foi possível investigar fenômenos como a transição de fase induzida por laser e desenvolver aplicações tecnológicas em áreas como litografia e sensoriamento de gases. Ficou destacada nesta tese o grande potencial de investigação da microscopia Raman confocal na área de nanomateriais. / A refined study of films derived from vanadium pentoxide gel was carried out based on spectroscopic and microscopic techniques, aiming a better understanding of this material on a microscopic scale. It was demonstrated that the vanadium pentoxide gel consists of a suspension of anisotropic nanoparticles which remains stable even at high concentrations. The structural and spectroscopic properties of such nanoparticles were reviewed and discussed, providing new insights at the state of the art. It was also investigated the occurrence of some relevant phenomena, such as the laser induced phase transition, and to develop new technological applications in areas such as gas sensing and lithography. The collection of results described in thesis highlighted a great research potential of confocal Raman microscopy, in the field of nanomaterials.

In the last decades, additive manufacturing (AM), also called three-dimensional (3D) printing, has advanced micro/nano-fabrication technologies, especially in applications like lightweight engineering, optics, energy, and biomedicine. Among these 3D printing technologies, two-photon polymerization (TPP) offers the highest resolution (even at the nanometric scale), reproducibility and the possibility to create monolithically 3D complex structures with a variety of materials (e.g. organic and inorganic, passive and active). Such active materials change their shape upon an applied stimulus or degrade over time at certain conditions making them dynamic and reconfigurable (also called 4D printing). This is particularly interesting in the field of medical microrobotics as complex functions such as gentle interactions with biological samples, adaptability when moving in small capillaries, controlled cargo-release profiles, and protection of the encapsulated cargoes, are required. Here we review the physics, chemistry and engineering principles of TPP, with some innovations that include the use of micromolding and microfluidics, and explain how this fabrication schemes provide the microrobots with additional features and application opportunities. The possibility to create microrobots using smart materials, nano- and biomaterials, for in situ chemical reactions, biofunctionalization, or imaging is also put into perspective. We categorize the microrobots based on their motility mechanisms, function, and architecture, and finally discuss the future directions of this field of research.