A novel approach to microfabrication based on stereolithography was presented. This fabrication process is referred to as, ‘Exposure Controlled Projection Lithography’ (ECPL). In the ECPL process, incident radiation, patterned by a dynamic mask, passes through a transparent substrate to cure photopolymer resin. By controlling the amount of exposure, the height field of the cured film can be controlled. An ECPL system was designed and assembled. Factors affecting the accuracy of the ECPL process in fabricating micron shaped features were identified and studied. A real-time in-situ photopolymerization monitoring system was designed and assembled within the ECPL system to identify the sources of variations present in the system. Parts are fabricated from the ECPL process because of polymerization (or cross-linking) of monomer resin using light energy. Photopolymerization is a complex process involving coupling between several phenomena. This process was modeled by utilizing an understanding of the known polymerization reaction kinetics with incorporating the effects of oxygen inhibition and diffusion. A material response model and a simulation tool to estimate the shape of a cured part resulting from photopolymerization was created. This model was used to formulate a process-planning method to estimate the manufacturing process inputs required to cure a part of desired shape and dimensions. The process planning method was validated through simulations and experiments.

Additive manufacturing methods have been developed from rapid prototyping techniques and are now being considered as alternatives to conventional techniques of manufacturing. Stereolithography is one of the main additive methods and is considered highly accurate and consistent. Polymers are used as stereolithography materials and exhibit features such as high strength-to-weight ratio, corrosion resistance, ease of manufacturing and good thermal and electrical resistance properties. However, they are sensitive to environmental factors such as temperature, moisture and UV light, with moisture being identified as one of the most important factors that affect their properties. Moisture generally has an adverse effect on the mechanical properties of polymers. Investigation of the effects of moisture on polymers can be carried out using a number of experimental techniques; however, the benefits of the depth sensing indentation method over bulk tests include its ability to characterise various mechanical properties in a single test from only a small volume of material and the investigation of spatial variation in mechanical properties near the surface. The aim of this research was to investigate the effects of varying relative humidity on the indentation behaviour of stereolithography polymers and to develop a modelling methodology that can predict this behaviour under various humidities. It was achieved by a combination of experimental and numerical methods. Depth sensing indentation experiments were carried out at 33.5 %, 53.8 %, 75.3 % and 84.5 % RH (relative humidity) and 22.5 °C temperature to investigate the effects of varying humidity on the micron scale properties of the stereolithography resin, Accura 60. In order to minimise the effects of creep on the calculated properties, appropriate loading and unloading rates with suitable dwell period were selected and indentation data was analysed using the Oliver and Pharr method (1992). A humidity control unit fitted to the machine was used to condition the samples and regulate humidity during testing. Samples were also preconditioned at 33.5 %, 53.8 %, 75.3 % and 84.5 % RH using saturated salt solutions and were tested at 33.5 % RH using humidity control unit. It was seen that properties such as indentation depth increased and contact iv hardness and contact modulus decreased with increasing RH. The samples conditioned and tested using the humidity control unit at high RH showed a greater effect of moisture than the preconditioned samples tested at 33.5 % RH. This was because the samples preconditioned at high RH exhibited surface desorption of moisture when tested at ambient RH, resulting in some recovery of the mechanical properties. In order to investigate these further, tests were performed periodically on saturated samples after drying. Ten days drying of samples conditioned for five days at 84.5 % RH provided significant, though not complete, recovery in the mechanical properties. These tests confirmed that Accura 60 is highly hygroscopic and its mechanical properties are a function of RH and removal of moisture leads to a significant recovery of the original mechanical properties.

Cette étude s'inscrit dans le cadre du développement de nouveaux matériaux pour la fabrication additive. Notre objectif est la fabrication de pièces comprenant un alliage métallique complexe (CMA) à l'aide d'un laser UV de stéréolithographie. L'alliage choisi est un alliage quasicristallin dominé par une phase icosaédrique du système AlCuFeB. Des poudres brutes d'atomisations ont été caractérisées par diffractions des rayons X et analyse thermique différentielle. Nous avons montré une bonne absorbance optique de la poudre dans le domaine UV-visible qui rend possible un début de frittage sous l'effet du laser correspondant à la formation de pontages entre les grains à une température d'environ 820°C. Concernant la fabrication à partir d'une suspension de poudres dans un liant, nous avons étudié les propriétés de mouillage des particules AlCuFeB et optimisé un mélange avec une résine époxy chargée par 20 % vol. de particules CMA. L'absorption optique de la suspension dans le domaine UV est suffisante pour fabriquer une pièce composite par stéréolithographie. La granulométrie utilisée est inférieure à 25 µm. Nous avons ainsi réussi à fabriquer des pièces de 14 mm de hauteur, en additionnant des couches de 50 µm. À partir des pièces réalisées, nous avons caractérisé la dureté et les propriétés tribologiques de ce nouveau matériau composite. La dureté des pièces ainsi fabriquées est supérieure à celle de la résine seule et atteint 88 Shore D. Nous avons également mis en évidence une amélioration de 30 % du coefficient de frottement et une diminution du volume d'usure de 40 % par rapport au matériau de la matrice époxy. Ces propriétés rendent attractif ce nouveau matériau composite pour la fabrication par stéréolithographie / This study aimed at developing new materials for additive manufacturing. We focused on producing parts containing complex metallic alloys (CMA) using a UV laser used for stereolithography. The selected intermetallic is a quasicrystalline alloy dominated by the icosahedral phase in the system AlCuFeB. The raw powders produced by gas atomization were characterized by X-ray diffraction and differential thermal analysis. The powders exhibit good optical absorption properties in the UV-visible range allowing direct laser sintering as evidenced by the formation of bridges between the grains at a temperature of about 820°C. In a second step, we have considered the manufacturing of parts made of a suspension of CMA powders in a binder. We have studied the wetting properties of the particles AlCuFeB and optimized a mixture consisting of an epoxy resin filled with 20 % vol. of CMA particles. The optical absorption of the suspension in the UV range was sufficient to produce composite parts by stereolithography. The particle size used was smaller than 25 micrometers. We have managed to make parts reaching 14 mm in height by adding layers with a thickness of 50 microns. Using test samples, we have characterized the hardness and the tribological properties of this new composite material. The hardness of the parts produced by stereolithography is larger than that of epoxy parts and reaches 88 Shore D. We have also shown a 30 % reduction of the friction coefficient as well as a 40 % reduction of wear losses compared to the epoxy matrix. These properties make attractive this new composite material for stereolithography applications

The photopolymerization of multifunctional acrylates leads to the formation of a complex and insoluble network due to cross-linking. This characteristic is a useful property for stereolithography applications, where solid parts of the desired shape are cured using a pre-determined energy exposure profile. Traditionally, the required energy exposure is determined using a critical energy--depth of penetration, or Ec--Dp, model. The parameters Ec and Dp, are usually fit to experimental data at a specific resin composition and cure intensity. As a result, since the Ec--Dp model does not explicitly incorporate cure kinetics, it cannot be used for a different set of process conditions without first obtaining experimental data at the new conditions. Thus, the Ec--Dp model does not provide any insight when a new process needs to be developed, and the best processing conditions are unknown. The kinetic model for multifunctional acrylate photopolymerization presented here is based on a set of ordinary differential equations (ODE), which can be used to predict part height versus exposure condition across varying resin compositions. Kinetic parameter information used in the model is obtained by fitting the model to double bond conversion data from Fourier Transform Infrared Spectroscopy (FTIR) measurements. An additional parameter, the critical conversion value, is necessary for determining the formation of a solid part of the desired height. The initial rate of initiation, Ri, combines all the factors that impact part height, and therefore, it is an important quantity that is required in order to find the critical conversion value. The critical conversion value is estimated using the Ri and Tgel value from microrheology measurements. Information about network connectivity, which can be used to get properties such as molecular weight, cannot be derived from models using traditional mass-action kinetics for the cross-linking system. Therefore, in addition to modeling the reaction using the ODE based model, the results from a statistical model based on Kinetic Monte Carlo (KMC) principles are also shown here. The KMC model is applicable in situations where the impact of chain length on the kinetics or molecular weight evolution is of interest. For the present project, the detailed information from network connectivity was not required to make part height predictions, and the conversion information from the ODE model was sufficient. The final results show that the kinetic ODE model presented here, based on the critical conversion value, captures the impact of process parameters such as initiator concentration, light intensity, and exposure time, on the final part height of the object. In addition, for the case of blanket cure samples, the part height predictions from the ODE model make comparable predictions to the Ec--Dp model. Thus, the ODE model presented here is a versatile tool that can be used to determine optimum operating conditions during process development.

Mask Projection micro Stereolithography (MPuSLA) is an additive manufacturing process used to build physical components out of a photopolymer resin. Existing MPuSLA technology cut the CAD model of part into slices by horizontal planes and the slices are stored as bitmaps. A layer corresponding to the shape of each bitmap gets cured. This layer is coated with a fresh layer of resin by lowering the Z-stage inside a vat holding the resin and the next layer is cured on top of it. In our Thick-film MPuSLA(TfMPuSLA) system, incident radiation, patterned by a dynamic mask, passes through a fixed transparent substrate to cure photopolymer resin. The existing MPuSLA fabrication models can work only for controlling the lateral dimension, without any control over the thickness of the cured part. The proposed process plan controls both the lateral dimensions and the thickness of profile of the cured part. In this thesis, a novel process planning for TfMPuSLA method is developed, to fabricate films on fixed flat substrate. The process of curing a part using this system is analytically modeled as the column cure model. It is different from the conventional process - layer cure model. Column means that a CAD model of part is discretized into vertical columns instead of being sliced into horizontal layers, and all columns get cured simultaneously till the desired heights. The process planning system is modularized into geometrical, chemical, optical, mathematical and physical modules and validated by curing test parts on our system. The thesis formulates a feasible process planning method, providing a strong basis for continued investigation of MPuSLA technology in microfabrication, such as micro lens fabrication.

Ce mémoire présente la synthèse et la caractérisation du matériau composite Ce-TZP/Al2O3 et l’étude de ce matériau dans une mise en forme par impression 3D de type stéréolithographie (SLA). Le matériau Ce-TZP présente une résistance au vieillissement en milieu aqueux (par transformation martensitique de la phase tétragonale vers la phase monoclinique) accrue en comparaison à Y-TZP. L’ajout d’alumine (Al2O3) comme seconde phase confère au matériau des propriétés mécaniques (résistance à la flexion en particulier) similaires à Y-TZP. La mise en forme par SLA offre la possibilité de fabriquer des objets avec des structures complexes tout en limitant l’utilisation et la perte de matière en comparaison à la fabrication soustractive, bien connue dans le domaine dentaire.Le composite Ce-TZP/Al2O3 a été synthétisé à partir d’une poudre Ce-TZP à laquelle est ajoutée de l’Al2O3 selon deux protocoles : la méthode Pechini modifiée et la méthode Isopropoxyde. Les études dilatométriques et microstructurales des composites ont montré que le matériau obtenu selon la méthode Isopropoxyde était plus homogène. Cette synthèse a donc été sélectionnée pour réaliser l’étude du frittage. Les conditions optimales résultants de cette étude (rampe de 300 °C/h, T°palier de 1500 °C pendant 1h, air), permettent d’atteindre une densité relative de l’ordre de 98% avec une taille de grains submicronique pour les deux phases.Des formulations photoréticulables sous exposition UV, chargées avec ce composite ainsi qu’avec le matériau de référence Y-TZP, ont été développées et étudiées afin de pouvoir mettre en forme ces matériaux par SLA. Avant utilisation dans le procédé, les formulations ont été caractérisées d’un point de vue rhéologique, thermique et également d’un point de vue de la réactivité sous exposition UV. Ces caractérisations ont permis de déterminer l’influence de la nature et de la taille des particules sur la réactivité principalement, paramètre également gouvernée par la composition des résines et notamment par le système amorceur, composé de un ou plusieurs photoinitiateur(s). Pour finir, les pièces fabriquées par SLA ont été frittées et caractérisées d’un point de vue mécanique et microstructural. / This thesis presents the synthesis and characterization of Ce-TZP/Al2O3 composite material and the study of this material in stereolithography process (SLA). Ce-TZP material exhibits an enhanced resistance to low temperature degradation (materialized by the tetragonal/monoclinic phase transformation) compared to Y-TZP. The addition of alumina (Al2O3) as a second phase gives to the material mechanical properties (especially flexural strength) similar to Y-TZP. SLA shaping offers the ability to make objects with complex structures while limiting the use and loss of material compared to subtractive manufacturing, well known in the dental field.The Ce-TZP/Al2O3 composite was synthesized from a Ce-TZP powder mixed with Al2O3 added according to two protocols: the modified Pechini method and the Isopropoxide method. The dilatometric and microstructural studies of the composites have showed that the material obtained by the Isopropoxide method was more homogeneous. This synthesis was therefore selected to carry out the sintering study. The optimal conditions resulting from this study (heating rate of 300 °C/h, T°soak of 1500 °C for 1h, air) allow to reach a relative density of 98 % with a submicron grain size for the two phases.Photocurable under UV exposure formulations, loaded with this composite as well as with the reference material Y-TZP, have been developed and studied in order to be able to shape these materials by SLA. Prior to use in the process, the formulations were characterized from a rheological, thermal and also from a viewpoint of reactivity under UV exposure. These characterizations made it possible to determine the influence of the nature and the size of the particles on the reactivity mainly, also governed by the composition of the resins and in particular by the initiator system, composed of one or more photoinitiator(s). Finally, the parts manufactured by SLA were sintered and characterized from a mechanical and microstructural point of view.

abstract: In this study, the stereolithography (SLA) 3D printing method is used to manufacture honeycomb-shaped flat sorbents that can capture CO2 from the air. The 3D-printed sorbents were synthesized using polyvinyl alcohol (PVA), propylene glycol, photopolymer resin, and an ion exchange resin (IER). The one-factor-at-a-time (OFAT) design-of-experiment approach was employed to determine the best combination ratio of materials to achieve high moisture swing and a good turnout of printed sorbents. The maximum load limit of the liquid photopolymer resin to enable printability of sorbents was found to be 44%. A series of moisture swing experiments was conducted to investigate the adsorption and desorption performance of the 3D-printed sorbents and compare them with the performance of IER samples prepared by a conventional approach. Results from these experiments conducted indicate that the printed sorbents showed less CO2 adsorptive characteristics compared to the conventional IER sample. It is proposed for future research that a liquid photopolymer resin made up of an IER be synthesized in order to improve the CO2-capturing ability of manufactured sorbents. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2020

This dissertation focuses on developing 3D printing as a fabrication method for microfluidic devices. Specifically, I concentrate on the 3D printing approach known as Digital Light Processing stereolithography (DLP-SLA) in which serially projected images are used to sequentially photopolymerize layers to build a microfluidic device. The motivation for this work is to explore a much faster alternative to cleanroom-based microfabrication that additionally offers the opportunity to densely integrate microfluidic elements in compact 3D layouts for dramatic device volume reduction. In the course of my research, an optical approach was used to guide custom resin formulation to help create the interconnected hollow regions that form a microfluidic device. This was based on a new a mathematical model to calculate the optical dose delivered throughout a 3D printed part, which also explains the effect of voids. The model was verified by a series of 3D printed chips fabricated with a commercial 3D printer and a custom resin. Channels as small as 108 µm x 60 µm were repeatably fabricated. Next, highly compact active fluidic components, including valves, pumps, and multiplexers, were fabricated with the same 3D printer and resin. The valves achieved a 10x size reduction compared with previous results, and were the smallest 3D printed valves at the time. Moreover, by adding thermal initiator to thermally cure devices after 3D printing, the durability of 3D printed valves was improved and up to 1 million actuations were demonstrated.To further decrease the 3D printed feature size, I built a custom 3D printer with a 385 nm LED light source and a 7.56 µm pixel pitch in the plane of the projected image. A custom resin was also developed to take advantage of the new 3D printer's features, which necessitated developing a UV absorber screening process which I applied to 20 candidate absorbers. In addition, a new mathematical model was developed to use only the absorber's molar absorptivity measurement to predict the resin optical penetration depth, which is important for determining the z-resolution that can be achieved with a given resin. The final resin formulation uses 2-nitrophenyl phenyl sulfide (NPS) as the UV absorber. With this resin, along with a new channel narrowing technique, I successfully created flow channel cross sections as small as 18 µm x 20 µm.With the custom 3D printer, smaller valves and pumps become possible, which led to the invention of a new method of creating large numbers of high density chip-to-chip microfluidic interconnects based on either simple integrated microgaskets (SIMs) or controlled-compression integrated microgaskets (CCIMs). Since these structures are directly 3D printed as part of a device, they require no additional materials or fabrication steps. As a demonstration of the efficacy of this approach, 121 chip-to-chip interconnects in an 11 x 11 array for both SIMs and CCIMs with an areal density of 53 interconnects per square mm were demonstrated, and tested up to 50 psi without leaking. Finally, these interconnects were used in the development of 3D printed chips with valves having 30x smaller volume than the valves we previously demonstrated. These valves served as a building block for demonstrating the miniaturization potential of an active fluid mixer using our 3D printing tools, materials, and methods. The mixer provided a set of selectable mixing ratios, and was designed in 2 configurations, a linear dilution mixer-pump (LDMP) and a parallelized dilution mixer-pump (PDMP), which occupy volumes of only 1.5 cubic mm and 2.6 cubic mm, respectively.

The diploma thesis is related to the preparation of hydroxyapatite complex structures by additive manufacturing known as Lithography based ceramics manufacturing – LCM. A photosensitive suspension containing hydroxyapatite particles was used for 3D printing of ceramic complex structures. The influence of printing parameters on the resulting macrostructure, microstructure, density, and dimensional accuracy was evaluated. The aim was to obtain ceramic components without delamination of the layers and optimise following post-processing steps (cleaning and thermal treatment). It was found that the exposure time has a significant effect on the dimensional accuracy of printed parts. During observation microstructure of printed parts, a microporosity at the interface of printed layers, which can cause delamination of several layers was identified. High-temperature dilatometry showed different temperature of beginning densification process in the longitudinal and perpendicular directions to the layers. That could be an initiation mechanism for delamination of the layers. X-ray diffraction analysis determined a single-phase composition of powder in photosensitive suspension and sintered parts. A commercial product LithaSol 20 was suggested as a suitable cleaning agent and efficiency of the ultrasound field for cleaning was demonstrated. Based on the thermogravimetric analysis an optimized cycle of heat treatment was designed. The optimisation led to time saving (49 hours), while maintaining density, dimensional accuracy and macrostructure of the 3D printed structures.

Idag sker en snabb ökning av handeln med varor och tjänster över hela världen. Detta ställer krav på att genom förpackningssystem bidra till effektivitet i distributionskanaler. Det vill säga att bygga upp system av förpackningar som möter de krav som ställs hos organisationerna som samverkar för distributionen av varor. Dock finns en bristande kunskap om distributionskanalers uppbyggnad och de krav som ställs vilket leder till problem. För att undvika suboptimeringar krävs en helhetssyn av distributionskanaler. Detta är särskilt viktigt för förpackningssystem som spelar en viktig roll i distributionen av varor. Små problem i systemen kan leda till stora problem genom hela kanalen. Identifieras inte brister längs flödet kan det vara svårt för förpackningsutvecklare att ta fram nya lösningar. Holistiskt belyser examensarbetet förpackningssystemets funktioner och brister i olika distributionskanaler. Genom en vidareutveckling och IT-fierad modell presenteras systemets utförande och tänkbara förbättringsförslag längs hela logistikflödet. Syftet med examensarbetet är att påvisa att en holistisk syn kan bidra till att skapa effektivitet i distributionskanaler. Genom att skapa en modell belysa förpackningssystems bidrag till ett effektivt distributionsflöde, det vill säga flödet genom en kanal. Vidare generera analyserbar data om hur små förändringar på förpackningssystem skulle kunna leda till ökad effektivitet genom hela distributionsflödet. För att svara på de ställda frågorna har litteraturstudier och fallstudier gjorts. För att mäta förpackningssystems effektivitet i distributionskanaler har verktyget Packaging Scorecard utnyttjats. Vidare har IT-baserade verktyg använts. Fallstudier visar att små förändringar kan bidra till effektivt utnyttjande av förpackningssystem i hela distributionskanalen. En vidareutveckling av Packagning Scorecard med tillämpning av CapePack- och CAD-verktyg har resulterat i en ny modell. Resultatet visar att modellen kan bidra till ökad förståelse för hur förpackningssystem kan skapa effektivitet. Genom tillämpning av verktygen CapePack och CAD kan förpackningsrelaterade problem längs distributionskanalen illustreras för vidare analys. Arbetet har bidragit till en verifiering av verktyget och har banat väg för en IT-fiering. / Today the trade with products and services are fast moving on the global market place. This requires that the packaging system should be able to create efficiency in distribution channel. Still there is a lack of knowledge in development of the distribution channel. This leads to problems. A holistic view of the distribution channels is needed to avoid sub optimisations. This is especially important regarding packaging systems that are important for the distribution of goods. Minor problems in the system may lead to major problems in the distribution channel. It can be difficult for the designers of packaging to develop new solutions if insufficiencies are not identified in the distribution flow. The master thesis illustrates a holistic view of the packaging system’s benefit and lack in functionalities in distribution channel. Through development and an IT-fied model the systems implementation and possible proposals of improvements can be done in the distribution flow. The purpose of the master thesis has been to prove that a holistic approach may contribute to an effective distribution flow. It has also been to generate analysable data about how minor changes in packaging systems may lead to increased efficiency through the entire distribution chain. Case studies and Literature studies have been done to find answers to the questions. Packaging Scorecard has been used to measure performance of the packaging systems. Further has an IT based tool been used. The case study shows that minor changes may contribute to efficient usage of packaging systems in the complete distribution channel. Further developments of the Packaging Scorecard applying CapePack and CAD tools have resulted in a new model. The result shows that the model may contribute to increase the understanding of how the packaging systems can create efficiency. Package related problems in the distribution channel can be illustrated and analysed by using the tools CapePack and CAD .The work has contributed to a validation of the tool and also introduction for the use of IT.