Background Brain biopsy of intracranial lesions is often necessary to determine specific therapy. The cost of the currently used stereotactic rigid frame and optical tracking systems for brain biopsy in dogs is often prohibitive or accuracy is not sufficient for all types of lesion. Objectives To evaluate the application accuracy of an inexpensive magnetic resonance imaging-based personalized, 3D printed brain biopsy device. Animals Twenty-two dog heads from cadavers were separated into 2 groups according to body weight (<15 kg, >20 kg). Methods Experimental study. Two target points in each cadaver head were used (target point 1: caudate nucleus, target point 2: piriform lobe). Comparison between groups was performed using the independent Student's t test or the nonparametric Mann-Whitney U Test. Results The total median target point deviation was 0.83 mm (range 0.09-2.76 mm). The separate median target point deviations for target points 1 and 2 in all dogs were 0.57 mm (range: 0.09-1.25 mm) and 0.85 mm (range: 0.14-2.76 mm), respectively. Conclusion and Clinical Importance This magnetic resonance imaging-based 3D printed stereotactic brain biopsy device achieved an application accuracy that was better than the accuracy of most brain biopsy systems that are currently used in veterinary medicine. The device can be applied to every size and shape of skull and allows precise positioning of brain biopsy needles in dogs.

The reliance on low-viscosity and photoactive resins limits the accessible properties for vat photopolymerization (VP) materials required for engineering applications. This has limited the adoption of VP for producing end-use parts, which typically require high MW polymers and/or more stable chemical functionality. Decoupling the viscosity and molecular weight relationship for VP resins has been completed recently for polyimides and highperformance elastomers by photocuring a scaffold around polymer precursors or polymer nanoparticles, respectively. Both of these materials are first shaped by printing a green part followed by thermal post-processing to achieve the final part properties. This dissertation focuses on improving the processability of these material systems by (i) investigating the impact of scaffold architecture and polysalt monomer composition on photocuring, thermal post-processing, and resulting thermomechanical properties and (ii) developing a Monte Carlo ray-tracing (MCRT) simulation to predict light scattering and photocuring behavior in particle-filled resins, specifically zinc oxide nanoparticles in a rigid polyester resin and styrene butadiene rubber latex resin. The first portion of the dissertation introduces VP of a tetra-acid and half-ester-based polysalt resin derived from 4,4'-oxydiphthalic anhydride and 4,4-oxydianiline (ODPA-ODA), a fully aromatic polyimide with high glass transition temperature and thermal stability. This polyimide, and polyimides like this, find use in demanding industries such as aerospace, automotive and electronic applications. The author evaluated the hypothesis that a non-bound triethylene glycol dimethacrylate (TEGDMA) scaffold would facilitate more efficient scaffold burnout and thus achieve parts with reduced off-gassing potential at elevated temperatures. Both resins demonstrated photocuring and were able to print solid and complex latticed parts. When thermally processed to 400 oC, only 3% of the TEGDMA scaffold remained within the final parts. The half-ester resin exhibits higher char yield, resulting from partial degradation of the polyimide backbone, potentially caused by lack of solvent retention limiting the imidization conversion. The tetra-acid exhibits a Tg of 260oC, while the half-ester displays a higher Tg of 380 oC caused by the degradation of the polymer backbone, forming residual char, restricting chain mobility. Solid parts displayed a phase-separated morphology while the half-ester latticed parts appear solid, indicating solvent removal occurs faster in the half-ester composition, presumably due to reduced polar acid functionality. This platform and scaffold architecture enables a modular approach to produce novel and easily customizable UV-curable polyimides to easily increase the variety of polyimides and the accessible properties of printed polyimides through VP. The second section of this dissertation describes the creation and validation of a MCRT simulation to predict light scattering and the resulting photocured shape of a ZnO-filled resin nanocomposite. Relative to prior MCRT simulations in the literature, this approach requires only simple, easily acquired inputs gathered from dynamic light scattering, refractometry, UV-vis spectroscopy, beam profilometry, and VP working curves to produce 2D exposure distributions. The concentration of 20 nm ZnO varied from 1 to 5 vol% and was exposed to a 7X7 pixel square ( 250 µm) from 5 to 11 s. Compared to experimentally produced cure profiles, the MCRT simulation is shown to predict cure depth within 10% (15 µm) and cure widths within 30% (20 µm), below the controllable resolution of the printer. Despite this success, this study was limited to small particles and low loadings to avoid polycrystalline particles and maintain dispersion stability for the duration of the experiments. Expanding the MCRT simulation to latex-based resins which are comprised of polymer nanoparticles that are amorphous, homogeneous, and colloidally stable. This allows for validating the MCRT with larger particles (100 nm) at higher loadings. Simulated cure profiles of styrene-butadiene rubber (SBR) loadings from 5 vol% to 25 vol% predicted cure depths within 20% ( µm) and cure widths within 50% ( µm) of experimental values. The error observed within the latex-based resin is significantly higher than in the ZnO resin and potentially caused by the green part shrinking due to evaporation of the resin's water, which leads to errors when trying to experimentally measure the cure profiles. This dissertation demonstrates the development of novel and functional materials and creation process-related improvements. Specifically, this dissertation presents a materials platform for the future development of unique photocurable engineering polymers and a corresponding physics-based model to aid in processing. / Doctor of Philosophy / Vat Photopolymerization (VP) is a 3D printing process that uses ultraviolet (UV) light to selectively cure liquid photosensitive resin into a solid part in a layer-by-layer fashion. Parts produced with VP exhibit a smooth surface finish and fine features of less than 100 µm (i.e., width of human hair). Recoating the liquid resin for each layer limits VP to low-viscosity resins, thus limiting the molecular weight (and thus performance) of the printed polymers accessible. Materials that are low molecular weight are limited in achieving desirable properties, such as elongation, strength, and heat resistance. Solvent-based resins, such as polysalt and latex resins have demonstrated the ability to decouple the viscosity and molecular weight relationship by eliminating polymer entanglements using low-molecular-weight precursors or isolating high-molecular-weight polymers into particles. This dissertation focuses on expanding and improving the printability of these methods. The second chapter of the dissertation investigates the impact of scaffold architecture in printing polyimide polysalts to improve scaffold burnout. Polysalts are polymers that exist as dissolved salts in solution, with each monomer holding two electronic charges. When heated, the solvent evaporates and the monomers react to form a high molecular-weight polymer. While previous work featured a polysalt that was covalently bonded to the monomers, the polysalt in this work is made printable by co-dissolving a scaffold. The polysalt resins are photocured and thermally processed to polymerize and imidize into a high-molecular-weight polymer, while simultaneously pyrolyzing the scaffold. Using a co-dissolved scaffold allows the investigation of two different monomers of tetra-acid and half-ester functionality. The half-ester composition underwent degradation during heating, increasing the printed parts' glass transition or softening point. The scaffold had little impact on the polysalt polymerization or final part properties and was efficiently removed, with only 3% remaining in final parts. The composition and properties of the monomers selected played a bigger role due to partial degradation altering the properties of the final parts. Overall, this platform and scaffold architecture allows for a larger number of polyimides to be accessible and easily customizable for future VP demands. The third chapter describes the challenges of processing photocurable resins that contain particles due to the UV light scattering in the resin vat during printing. When the light from the printer hits a particle, it is scattered in all directions causing the layer shape to be distorted from the designed shape. To overcome this, a Monte Carlo ray-tracing (MCRT) simulation was developed to mimic light rays scattering within the resin vat. The simulation was validated by comparing simulation results against experiment trials of photocuring resins containing 20nm zinc oxide (ZnO) nanoparticles. The MCRT simulation predicted all the experimental cure depths within 10% (20 µm) and cured widths within 30% (15 µm) error. Despite the high accuracy, this study was limited to small particles and low concentrations. Simulating larger particles is difficult as the simulation assumes each particle to be uniform throughout its volume, which is atypical of large ceramic particles. The fourth chapter enables high particle volume loading by using a highly stretchable styrene-butadiene rubber (SBR) latex-based resin. Latex-based resins maintain low viscosity by separating large polymer chains into nano-particles that are noncrystalline and uniform. When the chains are separated, they cannot interact or entangle, keeping the viscosity low even at high concentrations (>30 vol%). Like the ZnO-filled resin, the latex resin is experimentally cured and the MCRT simulation predicts the resulting cure shape. The MCRT simulation predicted cure depths within 20% (100 µm) and over-cure widths within 50% (100 µm) of experimental values. This error is substantially higher than the ZnO work and is believed to be caused by the water evaporating from the cured resin resulting in inconsistent measurements of the cured dimensions.

The Automated Design and Manufacturing Laboratory (ADML) is an automated assembly line located in the Engineering Product and Innovation Center (EPIC) that serves as the lab component for the course ME345: Automation and Manufacturing Methods. Over the semester the students learn how to program each automated component of the system, including Computer Numerically Controlled (CNC) mills, Universal Robot's 6 axis robotic arm, cameras, and Programmable Logic Controllers (PLC). Students then learn how to integrate each component together to develop a completely automated manufacturing process using an in-house manufacturing execution software. This integrated system is then used by the students to automatically manufacture new products of their own design that provide a societal benefit. Since 2019 multiple undergraduate students have worked on augmenting the ADML's capability with printing electronics by implementing Direct Ink Writing (DIW) based 3D printing and vacuum based pick and place into the ADML's assembly robot. Using these new capabilities, students in the ME345 will be able to design and manufacture electronic circuits. Moreover, a graduate level course will be developed based on this new addition to the ADML. The aim of this Thesis is to continue the work of previous students by finalizing the hardware and software necessary for the pick and place of electronic components and developing a conductive ink for electrical wiring and interconnects. A three component ink comprised of silver flake and a copolymer solution of acrylates/polytrimethylsiloxymethacrylate in a isododecane solvent was developed. This ink is biocompatible so it can be used by students without any hazard concern. It also exhibits a high degree of adhesion to the high-density polyethylene (HDPE) stock parts currently used in the ADML to ensure strong bonding to the electrical components. The mixing process, ink ingredient concentrations, and print parameters (i.e., extrusion pressure, print speed, and nozzle standoff distance) were optimized for compatibility with DIW based 3D printing, consistent and clog-free extrusion throughout the printing process, print fidelity, and a high electrical conductivity within approximately 1-2 orders of magnitude of bulk silver. / 2025-05-24T00:00:00Z

Intra-Body Communication (IBC) is a prospective technology where human tissue may be used as a signal medium in order to transmit useful data within the human body. Proposed applica- tions of this technology are prosthetics control or implanted device communication, potentially by establishing an Intra-Body Area Network (IBAN), which could further be enhanced by other IoT applications and 5G radio systems. Previous research at Uppsala University has shown the fat tissue to be a promising medium due to its low permittivity and loss tangent. This form of implementation is named Fat-IBC. This thesis aimed to produce a Fat-IBC enabled device, as a proof of concept. This project successfully produced and characterized phantom tissue, produced a basic demonstrator device in the form of a 3D-printed arm prosthetic, and integrated a wireless communication system into the arm prosthetic. The communication system was implemented using Arduino microcontrollers and XBee RF modules, based on the 802.15.4-based ZigBee protocol at 2.45 GHz. Muscle, fat, and skin phantom tissues were produced, with the muscle tissue being similar to other comparable tissue samples, while the fat and skin tissues deviated from such samples. A signal loss transmission test measured a -67 dB loss over 20 cm of fat tissue. Several potential issues with production and measurement were discussed. The arm demonstrator device was also tested by transmitting the control signal across phantom fat tissue, being fully functional through 10cm of tissue, and of limited function across 20cm of tissue.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24849号 / 工博第5166号 / 新制||工||1987(附属図書館) / 京都大学大学院工学研究科機械理工学専攻 / (主査)教授 泉井, 一浩, 教授 松原, 厚, 教授 平山, 朋子 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The arrival on the market of a new kind of CNC machines which can both add and remove material to an object paved the way to a new approach to the problem of repairing damaged components. The additive operation is performed by a Direct Laser Deposition (DLD) tool, while the subtractive one is a machining task. Up to now, repair operations have been carried out manually and for this reason they are errors prone, costly and time consuming. Refurbishment can extend the life of a component, saving raw materials and resources. For these reasons, using a precise and repeatable CNC machine to repair valuable objects is therefore very attractive for the sake of reliability and repeatability, but also from an economical and environmental point of view. One of the biggest obstacles to the automation of the repairing process is represented by the fact that the CAM software requires a solid CAD model of the damage to create the toolpaths needed to perform additive operations. Using a 3D scanner the geometry of the damaged component can be reconstructed without major difficulties, but figuring out the damage location is rather difficult. The present work proposes the use of octrees to automatically detect the damaged spot, starting from the 3D scan of the damaged object. A software named DUOADD has been developed to convert this information into a CAD model suitable to be used by the CAM software. DUOADD performs an automatic comparison between the 3D scanned model and the original CAD model to detect the damaged area. The detected volume is then exported as a STEP file suitable to be used directly by the CAM. The new workflow designed to perform a complete repair operation is described placing the focus on the coding part. DUOADD allows to approach the repairing problem from a new point of view which allows savings of time and financial resources. The successful application of the entire process to repair a damaged die for injection molding is reported as a case study. In the last part of this work the strategies used to apply new material on the worn area are described and discussed. This work also highlights the importance of using optimal parameters for the deposition of the new material. The procedures to find those optimal parameters are reported, underlying the pros and cons. Although the DLD process is very energy efficient, some issues as thermal stresses and deformations are also reported and investigated, in an attempt to minimize their effects.

With the rapid development of concrete 3D printing for construction projects, it is crucial to produce sustainable 3D-printed cementitious composites that meet the required fresh and hardened properties. This study investigates the application of cellulose-based nanomaterials (CN) (i.e., abundant natural polymers) that can improve the mechanical properties of cement-based materials – in 3D-printed cementitious composites of ordinary portland cement (OPC) and alkali-activated materials (AAMs). A combination of low calcium fly ash and ground granulated blast-furnace slag was used as the precursor in AAM systems. This work examines the 3D-printed mixtures with varying binders and mixture proportions and with different dosages of cellulose-based nanomaterial known as cellulose nanocrystals (CNC) to optimize the formulation for the production of sustainable high-performance 3D-printed elements. A suite of experimental techniques was applied to study the impact of CNC on the fresh and hardened properties of the 3D-printed samples. The buildability of the alkali-activated mixtures was improved by increasing the CNC content, suggesting that the CNC performs as a viscosity-modifying agent in AAMs. The inclusion of CNCs up to 1.00% (by volume of the binder) improves the overall mechanical performance and reduces the porosity of 3D-printed OPC and heat-cured AAM samples. Further, the addition of CNC (up to 0.30%) in sealed-cured AAM samples improves their flexural strength due to the crack-bridging mechanism of CNCs. The addition of CNC densifies the microstructure of OPC samples by increasing the degree of hydration, however, no significant impact on the microstructure of AAMs is noticed. The OPC sample with CNC has approximately 25% increase in the degree of hydration at inner depths which can be attributed to the internal curing potential of CNC materials. The initial water absorption rate of heat-cured AAM samples is lower than the sealed-cured AAM samples and comparable to the OPC system. The developed printable “alkali-activated-CNC” composites can provide an overall reduction in the environmental impacts of the 3D-printed cementitious composites by eliminating/reducing the need for different chemical admixtures to improve 3D-printed material consistency and stability, and replacing 100% of portland cement with fly ash and slag. / Civil Engineering

This investigation aims to understand and improve the deposition quality and rates of cold spray for additive manufacturing in a way that is economically sound and without the detrimental temperature effects seen in traditional metallic additive manufacturing processes. It focuses on materials that are desired by the additive manufacturing community and built upon the current knowledge in cold spray. This thesis is presented as a collection of published, or soon to be published, manuscripts accompanied by an introduction, literature review, and conclusion. The effect of a non-spherical particle morphology was the first objective investigated. Titanium has been shown repeatedly to require pure helium at very high temperatures and pressures to get dense coatings, however, the unique coral-like morphology resulting from the Armstrong Process was revealed as a key to successful deposition with nitrogen. Using low pressure cold spray, under conditions that would be considered mild, a deposition efficiency of 100% and a porosity of nearly 0% was achieved. This is a promising approach for cold spray as a method for additive manufacturing of titanium parts. The low powder cost and the advantages of additive manufacturing could allow for a substantial cost savings in titanium part production when compared to traditional manufacturing methods. With these cost saving advantages, additive manufacturing of titanium using Armstrong process powder and CS could lead to a paradigm shift of titanium production, allowing titanium to enter markets that under traditional methods would be far too expensive. Unfortunately, this unique powder morphology was not available in other materials. To address the low deposition efficiency of the other metals of interest, such as aluminum and stainless steel, the concept of mixing the propellant gas was introduced in the second objective. Considering the relative costs of gases, powder, electricity, and labour, the second paper focuses on the concept of optimizing the amount of helium to produce the minimum component cost. It was found that for the specific stainless steel and aluminum alloy powders discussed, costs could be reduced by 44% and 59%, respectively, using the gas mixing system. However, no cost saving was found for the most inexpensive of the powders, pure aluminum. For gas mixing to be effective, the cost of helium must be offset by the cost of the powders. Therefore, low-cost powders, such as pure aluminum, results in pure nitrogen as the least expensive option. This however doesn’t address the low deposition efficiency that is preventing its adoption in cold spray additive manufacturing. The third objective addresses just this, an improvement in deposition efficiency without the introduction of expensive helium. In this study, aluminum particles were preheated using a novel particle preheater that does not clog. This resulted in a deposition efficiency increase of 260% with a minimal increase in electrical costs. These three objectives, while studied and published separately, all relate to the purpose of this work to improve the process economics without detrimental temperature effects. These findings have been (or will be) published in international peer reviewed journals to add to the collective knowledge.

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