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Govindarajan, Sudhanva RajTHE DESIGN OF A MULTIFUNCTIONAL INITIATOR-FREE SOFT POLYESTER PLATFORM FOR ROOM-TEMPERATURE EXTRUSION-BASED 3D PRINTING, AND ANALYSIS OF PRINTABILITY
Doctor of Philosophy, University of Akron, 2016, Polymer Science
A 3D printable functionalized polyester platform was developed using a coumarin pendant group as a photo-crosslinker. The coumarin pendant groups convert the copolyester from a viscous liquid to an elastomeric solid under 365 nm UV light at room temperature without the use of an initiator. Relatively hydrophobic variants of this platform (SC) was created using unsaturated aliphatic chains derived from soybean oil as pendant groups. A hydrogel variant (CPP) of this platform was created by using polyethylene glycol (PEG) as a backbone. Cell studies of the SC copolyester showed no toxic effects over short time scales. Rheological analysis demonstrated that all polymers over a range of molar feed ratios and molar masses were shear thinning. The SC platform has a very high entanglement molecular weight and has rheological behavior similar to that of an un-entangled brush. UV crosslinking of both SC and CPP platforms create thermosetting elastomeric solids. The relatively SC platform exhibits a high degree of fully reversible elastic deformation under shear due to chain extensibility and lack of trapped entanglements. Multiple pendant functional groups can be readily incorporated into this platform. Primary amine functionality was incorporated into the SC copolyester as a proof of concept. Extrusion based 3D printing (EBP) was successfully demonstrated on both platforms and FITC was successfully covalently clicked onto the primary amine functional group post-printing. Extrusion of the SC platform was accelerated due to UV extrusion. This might be due to Rouse-like behavior under shear coupled with excitation of cis double bonds in the unsaturated pendant groups. Examination of defects accumulated during the 3D printing process demonstrated that dynamic viscoelasticity due to print speed V affected the overall quality of the print. Interfacial chain relaxation institutes a lag-time between initial deposition and adhesion which increases with V. Deformability of the polymer substrate due to shear during deposition can negatively impact adhesion during this lag time, forming a defect. This phenomenon was modeled using two comprehensive equations.

Committee:

Abraham Joy, PhD (Advisor); Ali Dhinojwala, PhD (Committee Chair); Mesfin Tsige, PhD (Committee Member); Coleen Pugh, PhD (Committee Member); Jae-Won Choi, PhD (Committee Member)

Subjects:

Engineering; Materials Science; Physics; Polymer Chemistry; Polymers

Keywords:

3D Printing; Biomaterials; Polyesters; Patterning; Polymers; Extrusion; Extrusion Based Printing; Unentangled Melts; Rouse Regime; Extrusion; Rheology of Inks; 3D Printing Rheology; Printability

Swift, Nathan ButlerHEDGEMON: A HEDGEHOG-INSPIRED HELMET LINER
Master of Sciences, Case Western Reserve University, 2016, Physics
In contact sports like football and ice hockey, concussions are a common occurrence. Over 10% of athletes experience at least one concussion per season. Recent discoveries have emphasized the disastrous neurological consequences for people with a history of concussions, which include dementia, depression, and early-onset Alzheimer’s disease. Today’s helmet technology is woefully inadequate at mitigating concussions, especially in where the athlete’s head experiences rotational acceleration. With lawsuits mounting against leagues like the NFL, the survival of football may depend on solving the concussion problem. The startup Hedgemon, LLC has begun developing a promising impact protection technology based on hedgehog spines. If integrated into a football helmet liner, it could substantially reduce the concussion-causing acceleration of the brain induced by frequent in-game collisions. Adapted from a recently submitted SBIR Phase I grant proposal, this paper discusses in detail the technology at its current state of development and the exciting commercial opportunity.

Committee:

Edward Caner (Advisor); Robert Brown (Committee Member); Michael Martens (Committee Member)

Subjects:

Biomechanics; Biophysics; Entrepreneurship; Mechanics; Physics; Sports Medicine

Keywords:

Biomimicry; impact testing; helmet liner; hedgehog spines; football; concussion; 3D printing; rotational acceleration; linear acceleration

Bell, Alex E.Microscale Additive Manufacturing of Collagen Cell Culture Scaffolds
PhD, University of Cincinnati, 2015, Engineering and Applied Science: Biomedical Engineering
Communication between cells and their environment is a key influencing factor on cell fate in tissues. Through integrin receptors, cells can sense and respond to structural features of the extracellular matrix. Signaling-factor receptors can detect gradient changes in concentration of a multitude of soluble ligands. Both mechanical and biochemical signals are presented to cells in defined spatial patterns. One of the most important sets of signals for developing or regenerating tissue are those guiding the formation of a vascular supply. Vascular development is crucial to recapitulation of further tissue function. Replicating these 3D patterns in vitro is a considerable challenge for the long-term goal of engineering functional tissue replacements. Multiphoton crosslinking (MPC) is an additive manufacturing process using light-activated chemistry to produce crosslinking by the absorption of multiple photons. MPC is quadratically dependent on light intensity, allowing isolation of the reaction to the focal plane. With diffraction-limited optics, this provides 1 µm resolution. MPC has the potential to give unlimited 3D control of the structural and biochemical cues imparted by functional proteins and peptides at a sub-cellular scale. Potential benefits of MPC include both the ability to spatially isolate presentation of a given factor in a concentration-controlled manner and sequestering the factor to provide a sustained dose over an extended period of cell culture and tissue regeneration. The MPC technique is essentially applicable to any protein, as several amino acids can react with an excited radical species. MPC of protein substrates has not yet been utilized toward functional tissue engineering applications. This is due to multiple factors, including the need for the substrate protein to be soluble, form a stable 3D structure, and have the unexposed portion readily removed. Thus, MPC has been limited in use primarily to highly soluble proteins such as albumin, which is not effective as a tissue scaffold material. Patterning of functional proteins onto scaffolds using MPC has also been limited by the need for the unexposed materials to be removed from the scaffold following the patterning process. This has meant that the technique, thus far, is largely employed on synthetic hydrogels with peptide fragments. This dissertation encompasses studies that established new additive manufacturing methods for cellular scaffolds in dermal wound healing. Completion of this work has expanded the capability of MPC to allow 3D fabrication of type I collagen scaffolds with spatial control of local structural and biochemical signals at a sub-cellular scale. Initial studies were performed to assess the effectiveness of these scaffolds patterned with VEGF for the induction of vasculogenesis by spatially defining the presentation of vasculogenic signals. These materials were used in a form as near as possible to their native state in an attempt to present a signaling environment more similar to a native ECM. These studies were directed toward implementation in vasculogenic dermal wound scaffolds, but the methods used are generally applicable to creation of structural and chemical patterning in any TE/RM application.

Committee:

Vasille Nistor, Ph.D. (Committee Chair); J. Matthew Kofron, Ph.D. (Committee Member); Jason Shearn, Ph.D. (Committee Member); Lilit Yeghiazarian, Ph.D. (Committee Member)

Subjects:

Biomedical Research

Keywords:

Multiphoton fabrication;3D printing;tissue engineering;collagen scaffolds;additive manufacturing;vasculogenesis angiogenesis

Kuntz, Sarah LouiseFeasibility of Attaining Fully Equiaxed Microstructure through Process Variable Control for Additive Manufacturing of Ti-6Al-4V
Master of Science in Mechanical Engineering (MSME), Wright State University, 2016, Mechanical Engineering
One of the greatest challenges in additive manufacturing is fabricating titanium structures with consistent and desirable microstructure. To date, fully columnar deposits have been achieved through direct control of process variables. However, the introduction of external factors appears necessary to achieve fully equiaxed grain morphology using existing commercial processes. This work introduces and employs an analytic model to relate process variables to solidification thermal conditions and expected beta grain morphology at the surface of and at the deepest point in the melt pool. The latter is required in order to ensure the deposited microstructure is maintained even after the deposition of subsequent layers and, thus, the possibility of equiaxed microstructure throughout. By exploring the impact of process variables on thermal, morphological, and geometric trends at the deepest point in the melt pool, this work evaluates four commercial processes, estimates the range of process variables capable of producing fully equiaxed microstructure, and considers the expected size of the resultant equiaxed melt pool.

Committee:

Nathan Klingbeil, Ph.D. (Advisor); Joy Gockel, Ph.D. (Committee Member); Raghavan Srinivasan, Ph.D. (Committee Member)

Subjects:

Aerospace Materials; Engineering; Materials Science; Mechanical Engineering; Metallurgy; Morphology

Keywords:

additive manufacturing; 3D printing; titanium alloy; Ti64; Ti-6Al-4V; equiaxed morphology; equiaxed beta grains; solidification maps; process variable control; process parameter control; power, velocity, preheat; Rosenthal; Hunts criterion curve equations

Kay, RyanEffect of Raster Orientation on the Structural Properties of Components Fabricated by Fused Deposition Modeling
Master of Science, The Ohio State University, 2014, Mechanical Engineering
Fused deposition modeling (FDM) is a common form of additive manufacturing, which uses an extruded thermoplastic filament to produce complex three-dimensional parts. With the addition of high strength thermoplastics to the list of available materials, the use of FDM to build functional prototypes and end-use products has increased. In order to completely utilize the capabilities of FDM, it is necessary to understand the effects of various build parameters on the material properties of the part. This thesis characterizes the material properties of four different materials, ABS-m30i, PC-ABS, PC, and ULTEM, for three different raster configurations. To accomplish this, two different ASTM tensile testing standards were evaluated for their effectiveness when testing specimens created via FDM, and then, the chosen testing standard was used to perform tensile tests for the various raster orientations and materials. After determining the material properties, several other tests were conducted to investigate discrepancies between the measured and reported values. These tests included investigations into the effects of the batch size and the time parts were left at elevated temperatures on the strength of the parts. It was found that ASTM D3039 produced more consistent results than ASTM D638. From the results of the tensile tests, it was determined that specimens with rasters oriented in the direction of loading exhibited the highest tensile strengths. For specimens with rasters oriented in the direction of loading, the tensile strengths ranged from 85%-110% of the manufacturer’s reported values. Other configurations ranged from 62-75% of the reported values. The Young’s moduli ranged from 90-116% of the reported values when the rasters were oriented in the direction of loading. For the other raster orientations tested, the Young’s moduli ranged from 76%-93% of the reported values. Batch size was found to have a negligible effect on the part strength. Results suggested that the time parts were left at elevated temperatures had an effect on the part strengths, though more testing is required to make a definitive conclusion. Finally, due to the large differences in strengths between various raster orientations, it was concluded that designers should only refer to the mechanical properties of the raster orientation being used as opposed to the generic values reported by the manufacturer.

Committee:

Blaine Lilly (Advisor); Rebecca Dupaix (Committee Member); Jose Castro (Committee Member)

Subjects:

Engineering; Materials Science; Mechanical Engineering

Keywords:

raster orientation; tensile strength; FDM; fused deposition modeling; material properties; thermoplastics; 3D printing

Webber, Christina MarieProsthetic Sockets: Assessment of Thermal Conductivity
Master of Science, University of Akron, 2014, Biomedical Engineering
Current commercially available prosthetic liners and sockets insulate the residual limb, causing the temperature of the residual limb to increase. As a result, the residual limb sweats excessively, leading to numerous dermatologic conditions. These skin problems can impart physical and psychological burdens on the amputee patient and hinder their rehabilitation process. Overall, this study aimed to aid in the rehabilitation of amputee patients by specifically addressing the cause of the increased residual limb temperatures. This was accomplished in three aims. The first aim focused on quantifying the thermal barrier posed by materials currently used in prosthetic liners and sockets by measuring the materials’ thermal conductivities. All materials were shown to be significant insulators. The second aim approached the problem of increased temperatures by modifying a prosthetic socket, then using computer simulations to observe the temperature difference between the inner and outer socket walls. Three sockets were modeled: two modified sockets, each containing a cooling channel 0.5 cm in diameter; and a control socket. A greater temperature drop across the socket wall suggested that the socket could provide cooling benefits to the residual limb by allowing for heat to be drawn away from the limb, towards the cooling channels. Socket type and location on the socket were statistically significant factors affecting the predicted temperature difference. This finding suggests that modifications of a prosthetic socket could offer a cooling effect to amputee patients. Aim 3 focused on validating that computer simulation from Aim 2. 3D printed prototype sockets were constructed. The socket with the greatest observed average temperature differential was the socket with an eight revolution cooling channel in its wall. This finding suggests that socket modifications, like the cooling channel presented, could provide a cooling effect to the residual limb. Overall, this study showed that future iterations of prosthetic liners and sockets should take the thermal properties of the designs into account to provide the greatest benefit to amputee patients.

Committee:

Brian Davis, Dr. (Advisor); Marnie Saunders, Dr. (Committee Member); Narender Reddy, Dr. (Committee Member)

Subjects:

Biomechanics; Biomedical Engineering; Biomedical Research; Engineering; Polymers

Keywords:

prosthetics; thermal conductivity; novel prosthetic socket; socket design; thermal properties; temperature difference; cooling channel; 3D printing

Cater, Miriam ReginaPermeability and Porosity Reduction of Fused Deposition Modeling Parts via Internal Epoxy Injection Methods
Master of Science, The Ohio State University, 2014, Mechanical Engineering
Fused deposition modeling, or FDM, is a rapidly developing technology currently used in prototyping and some manufacturing areas. Available since the 1980s and commercialized by Stratasys in the 1990s, FDM has quickly become a standard in the area of rapid-prototyping or as it is most commonly known, 3D printing. FDM is known as an additive process in which a shape is created by extruding material into layers which are controlled by a computer to form the final shape. Some FDM machines allow the user to control various aspects of the layering process such as layer thickness, air gap between extrusions, process speed, contour angle, and extrusion width. These directly impact the final shape’s mass, density, strength, durability and permeability. This study looks into the various aspects of ensuring FDM permeability for its use in pressure applications utilizing different printable materials. Not only will this study recommend ideal machine settings in order to reduce porosity and design the optimal internal structure for the part, but will also suggest post-processing techniques based on injecting epoxy into the parts that will reduce porosity and decrease permeability. The two FDM machines that are used for testing samples are the Fortus 400mc and the Stratasys Dimension 1200es. The ultimate goal of this study is to understand how to create permeable plastic solutions in order to improve the use of FDM prototyping and manufacturing for high pressure applications, without compromising the part’s original exterior dimensions and surface finishes.

Committee:

Blaine Lilly (Advisor); Rebecca Dupaix (Committee Member); Jose Castro (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

FDM, Fused Depostion Modeling, 3D printing, porosity, permeability, epoxy, sealing

Pearson, KirkExperimental biomechanics of trinucleid fringe pits (Trilobita)
BA, Oberlin College, 2017, Geology
The morphometric uniqueness of the trinucleid family of fossil arthropods, known as the trilobites, has led to a considerable amount of attention in paleontology literature. In particular, the distinctive hourglass-shaped pits that dot their anterior have been the subject of debate for over a century. Though anatomically well understood, their function remains unknown. Many proposals have been suggested, including its use as a sieve for filter-feeding, a strong shield for defense, and a sensory mechanism to compensate for their blindness. Despite the wide range of speculations, no study has attempted to model these hypotheses experimentally. Flume experiments and mechanical strength tests using a tenfold scale, 3D-printed model of a trinucleid head suggest that the dominant theories for over a century, filter-feeding and skeletal strengthening, are not well supported. It is proposed that the results suggest that the pits are an ontogenetic signature that optimize the cephalon’s growth to be maximal, providing trinucleids with an excellent mechanism for plowing through fine-grained silts and clays.

Committee:

Karla Parsons-Hubbard (Advisor); Yolanda P. Cruz (Advisor); Dennis Hubbard (Committee Member); Steven F. Wojtal (Committee Member); Amanda Henck Schmidt (Committee Chair)

Subjects:

Biomechanics; Biophysics; Geology; Paleoecology; Paleontology

Keywords:

trilobites; functional morphology; CT scanning; 3D printing; modeling

Turner, Andrew JosephLow-Velocity Impact Behavior of Sandwich Panels with 3D Printed Polymer Core Structures
Master of Science in Mechanical Engineering (MSME), Wright State University, 2017, Mechanical Engineering
Sandwich panel structures are widely used in aerospace, marine, and automotive applications because of their high flexural stiffness, strength-to-weight ratio, good vibration damping, and low through-thickness thermal conductivity. These structures consist of solid face sheets and low-density cellular core structures, which are often based upon honeycomb topologies. The recent progress of additive manufacturing (AM) (popularly known as 3D printing) processes has allowed lattice configurations to be designed with improved thermal-mechanical properties. The aim of this work is to design and print lattice truss structures (LTS) keeping in mind the flexible nature of AM. Several 3D printed core structures were created using polymeric material and were tested under low-velocity impact loads. Different unit-cell configurations were compared to aluminum honeycomb cores that are tested under the same conditions. An impact machine was designed and fabricated following the ASTM D7136 Standard to correctly capture the impact response. The absorption energy as well as the failure mechanisms of lattice cells under such loads are investigated. The differences in energy-absorption capabilities were captured by integrating the load-displacement curve found from the impact response. Similar manufacturing and sandwich-panel-fabrication processes must be used to accurately compare the impact responses. It is observed that selective placement of vertical support struts in the unit-cell results in an increase in the absorption energy of the sandwich panels. Other unit-cell configurations can be designed with different arrangements of vertical struts into the well-known body centered cubic (BCC) LTS for further improvements in absorption energy capabilities.

Committee:

Ahsan Mian, Ph.D. (Advisor); Raghavan Srinivasan, Ph.D., P.E. (Committee Member); Joseph Slater, Ph.D., P.E. (Committee Member)

Subjects:

Automotive Materials; Engineering; Experiments; Mechanical Engineering; Polymers

Keywords:

Additive manufacturing; 3D Printing; Sandwich structures; Energy absorption; Low-velocity impact

Pangsrivinij, SuksantHigh Throughput Functional Material Deposition Using A Laser Hot Wire Process
Master of Sciences (Engineering), Case Western Reserve University, 2016, Materials Science and Engineering
Laser Hot-Wire (LHW) cladding is a wire-based, laser-assisted additive process of fusion joining. As the name suggests the filler wire is resistively heated prior to reaching the weld pool. The LHW process offers great benefits, relative to arc-based processes, in terms of high energy efficiency, excellent metallurgical control and high deposition rate. In work reported on in this thesis, two different material systems, Ti-6Al-4V alloy and the nickel-based superalloy 625, are experimentally evaluated through characterization of specimens created using the LHW process with a range of process parameters. Characterization includes chemistry of deposited metal, microstructure, selected mechanical properties, dimensions, and residual stress. Also, a rigorous analysis of energy efficiency was performed. All results are benchmarked relative to a laser/powder based additive manufacturing process. The result obtained in this work is anticipated to improve the understanding of the LHW process, expand its use to less common alloy systems, and promote its use as an industrially relevant form of additive manufacturing. The project that enabled this work is a collaboration between CWRU, Lincoln Electric, Alcoa Titanium & Engineering Products, and rp+m Incorporated.

Committee:

James McGuffin-Cawley (Advisor)

Subjects:

Aerospace Engineering; Engineering; Materials Science; Mechanical Engineering

Keywords:

laser; laser hot-wire; welding; 3d printing; titanium; nickel; deposition; cladding; additive manufacturing

Fitzgerald, Martha MooreDevelopment and 3D Printing of Interpenetrating Network Hydrogel Materials for use as Tissue-Mimetic Models
Master of Science, Miami University, 2015, Chemical, Paper & Biomedical Engineering
This thesis reports the development, and subsequent 3D printing, of a two-part polyacrylamide-alginate interpenetrating network (IPN) hydrogel material with tissue-mimetic properties. Two possible applications include medical simulation and tissue engineering. Material development was performed with single-parameter chemical concentration variations from a baseline formula to establish mechanical property trends. The concentrations of total monomer material and acrylamide crosslinker have the largest effect on elastic modulus and stress relaxation behavior, respectively. Results demonstrate that these hydrogels can be tuned to closely mimic both the elastic and viscoelastic behaviors of muscle tissue. Hardware alterations to a 3D printer allowed the two-part solution to be rapidly printed with high shape fidelity and similar mechanical properties to native tissue at a relatively low cost and on a large scale. The alginate-polyacrylamide material can be tuned in its bulk state, and 3D printed into constructs that are in the correct scale for use in tissue-mimetic applications.

Committee:

Jessica Sparks, PhD (Advisor); Jason Berberich, PhD (Committee Member); Justin Saul , PhD (Committee Member)

Subjects:

Biomedical Engineering; Chemical Engineering

Keywords:

Hydrogel; Interpenetrating network; stress relaxation; Muscle; tissue-mimetic; alginate-polyacrylamide; 3D printing; Viscoelastic; Simulation

Doustmohammadi, SaeideProduct Customization Through Digital Fabrication Technology
Master of Fine Arts, The Ohio State University, 2015, Industrial, Interior Visual Communication Design
The advancement of additive manufacturing technology, such as 3D printers, has introduced many novel opportunities into the world of design and fabrication. The goal of this research is to explore the applications of this technology in the domain of product customization. This thesis consists of two parts: First, it investigates the opportunities provided by the technology regarding the personal fabrication purposes and identifies three main categories of needs through conducting three preliminary case studies. The result of this part is used to identify and explore two key elements of customization: physical need and emotional preference. Then, these two elements are analyzed in mass manufacturing systems. The second part of this thesis investigates how digital fabrication technology can be integrated into the customization process to improve the user experience. To do this, a methodology is proposed in order to increase the role of user and his/her physical and emotional needs in the process of customization. In addition, a case study is conducted to actualize the various aspects of the methodology and to visualize it step by step. In this case study, a customized protective helmet is designed for a child suffering from epilepsy through directly collaborating with her and her mother. The focus of the proposed methodology is on making products that can appropriately address the users’ physical needs and at the same time properly respond to their emotional preferences and feelings. The methodology also emphasizes the role of designers in creating opportunities for users to benefit from the advancement of the digital fabrication technology regarding customization.

Committee:

Roozbeh Valamanesh, Prof. (Advisor); Elizabeth Sanders, Dr. (Committee Member); Staley David , Dr. (Committee Member)

Subjects:

Design; Technology

Keywords:

Digital Fabrication Technology; Personal Fabrication; Customization; 3D Printing, Additive Manufacturing

Huthman, Ibrahim O.3D Printing for Prestressed Concrete
Master of Science (MS), Ohio University, 2017, Civil Engineering (Engineering and Technology)
The rapid growth of 3D printing technology has led to the development of large scale 3D printers that can print in concrete and steel. The process of 3D printing in concrete does not use formwork and thus gives increased flexibility to designers, saves cost of labor and materials and reduces waste. These printers have been used to construct structural elements, full scale buildings and a steel bridge. However, the focus of this new age of 3D printers in the construction industry has been on buildings and structural elements. However, a significant part of concrete production in the world are on precast and prestressed girders. These girders are used in bridges, buildings and other structural systems. This necessitates a broadened focus to include 3D printing technology for the prestressed industry. To mitigate this gap, this research has taken the initiative to do a thoroug literature review of 3D printing technology in construction. This research also includes design, modeling and testing of effective I-girder shapes and small scale 3D printed Igirders. The results show the benefits of the proposed effective girder shapes in reducing end cracking and that 3D printing technology can be incorporated into the prestressed industry albeit increased investment in research, testing and implementation.

Committee:

Eric Steinberg (Advisor); Kenneth Walsh (Committee Member); Issam Khoury (Committee Member); Annie Shen (Committee Member)

Subjects:

Engineering

Keywords:

3D Printing; Prestressed Concrete; Formwork; Bridges

Passmore, Catherine M3D Printed Mini-Whegs Robot Design and Vibration Analysis
Master of Sciences (Engineering), Case Western Reserve University, 2017, EMC - Mechanical Engineering
A Mini-Whegs vehicle was designed, fabricated, and assembled consisting predominantly of 3D printed parts. 3DP Mini-Whegs is a fully functional, Bluetooth controlled, mobile quadruped approximately 6 ½ inches long. It’s a member of the Whegs family of robots, which all utilize rotating, spoked appendages, called wheel-legs. The unique geometry of these appendages introduces considerable vibrations to the system, making it difficult to integrate vibration sensitive equipment, such as cameras or sensors. A vibration analysis model was developed to simulate vibrations in the moving robot. Three wheel-leg designs were developed and analyzed to determine that stiffer spokes provide less vertical displacement and less stiff ones offer less angular displacements, and that four spoked wheel-legs are considerably more stable than three. Different front-to-back wheel-leg phase angles vary the vibrations but an optimal angle depends on application. Experiments investigated the validity of the simulation and verified the difference in stiffness of compared wheel-legs.

Committee:

Roger Quinn (Advisor); Richard Bachmann (Advisor); Clare Rimnac (Committee Member)

Subjects:

Design; Mechanical Engineering; Mechanics; Robotics; Robots

Keywords:

Whegs; Mini-Whegs; vibration; vibration analysis; mobile robot; robot; 3D printing; wheel-leg; vibration

Vijayakumar, DineshwaranManufacturing Carbon Nanotube Yarn Reinforced Composite Parts by 3D Printing
MS, University of Cincinnati, 2016, Engineering and Applied Science: Mechanical Engineering
Fused filament fabrication (FFF) is a 3D printing technology that translates plastic filaments into three-dimensional parts. Presently, there is an unmet demand to translate this technology into a full-scale manufacturing process. With advancements in hardware components and build preparation software, the main component that has been holding back progress in 3D Printing industry is the filament material. The majority of the plastic filaments in the market lack performance characteristics such as strength, durability and electrical properties. Reinforcing the standard plastic filaments with a strong multifunctional nanomaterial like Carbon Nanotubes (CNT) will drastically improve the capabilities of 3D Printed parts. In this research, several techniques were tested to implement custom fibers into standard plastic filaments. An innovative filament production system was developed to produce CNT yarn reinforced filaments. CNT yarn and Nomex filaments successfully demonstrated the ability to be 3D Printed.

Committee:

Mark Schulz, Ph.D. (Committee Chair); Woo Kyun Kim, Ph.D. (Committee Member); Vesselin Shanov, Ph.D. (Committee Member)

Subjects:

Mechanical Engineering; Mechanics

Keywords:

Carbon Nanotubes;3D Printing;Wire Coating filament extrusion;Filament production;Fused Filament Fabrication;Fiber reinforced 3D Printer filament

Sharan Kumar, VarunStudy of Binding Copper Powders by Electrochemical Deposition
MS, University of Cincinnati, 2016, Engineering and Applied Science: Mechanical Engineering
Additive manufacturing (AM) is a layer-by-layer manufacturing process that has a wide range of applications. Microparts manufactured by additive manufacturing are gaining prominence over traditional manufacturing methods due to their ability to process a wide range of materials, fabricate complex 3D microstructures and ease of use. AM processes have applications in diverse fields such as aerospace, automotive, medical devices and implants, electronics, and so on for fabricating complex microparts. This work evaluates the feasibility of binding metal powders to enable a novel micro additive manufacturing method based on localized electro-deposition. A single layer of copper powders were glued together with the help of Nickel from the electrolyte as a binder using a completely in-house built CNC stage and controller. Images from scanning electron microscopy (SEM) and Optical microscope along with X-ray spectroscopy studies have shown the gluing of copper powders with Nickel acting as a binder element. Mechanical characterization was done on the glued part and yield strength values were obtained. Further, Taguchi studies have been conducted to investigate the optimal process parameters required for minimum diameter of glued spot, layer thickness and yield strength. Analysis of Variance (ANOVA) and signal-to-noise ratio were used to determine the important levels of process parameters and the results were then experimentally verified. A mathematical model is developed and verified to predict yield strength values of the deposit. Experimental verification of the model was performed using different substrates with the same deposition parameters to verify the substrate effects involved in the predicted hardness value. It was found that the deviations in the film hardness values of deposits on different substrates under the same deposition parameters were within 8% of each other.

Committee:

Sundaram Murali Meenakshi, Ph.D. (Committee Chair); Thomas Richard Huston, Ph.D. (Committee Member); David Thompson, Ph.D. (Committee Member)

Subjects:

Mechanical Engineering; Mechanics

Keywords:

Electrodeposition;3D printing;micro additive manufacturing;localized electrodeposition;film hardness;ANOVA

Yelamanchi, BharatExperimental Study of Disruption of Columnar Grain Growth during Rapid Solidification
Master of Science in Engineering, Youngstown State University, 2015, Department of Mechanical and Industrial Engineering
Over the years, many studies have been conducted to study and analyze the grain structures of metal alloys in order for them to have superior structural and mechanical properties. In particular, columnar grains are observed predominantly during rapid solidification of molten metal. This leads to lower mechanical properties and requires expensive secondary heat-treatment processes. This study is aimed at disrupting the formation of columnar grain growth during rapid solidification using ultrasonic vibration and analyzes the effects on grain structure and mechanical properties. A MIG welder mounted on a low cost metal 3D printer was used to deposit ER70S-6 mild steel layers on a plate. A contact type ultrasonic transducer with control system to vary the frequency and power of the vibration was used. The effects of ultrasonic vibration were determined from the statistical analysis of microstructure using ImageJ and micro-indentation techniques on the deposited layer and heat affected zone. It was found that both frequency and interaction between frequency and power had significant impact on the refinement of average grain size up to 10.64% and increased the number of grains by approximately 41.78%. Analysis of micro-indentation tests showed that there was an increase of approximately 14.3% in micro-hardness and 35.77% in Young’s modulus due to the applied frequency during rapid solidification. Along with the results from this study, further efforts in modeling and experimentation of multi directional vibrations would lead to a better understanding of disrupting columnar grains in applications that use mechanical vibrations, such as welding, metal additive manufacturing, brazing, and the likes.

Committee:

Guha Manogharan, PhD (Advisor); Brett Conner, PhD (Committee Member); Darrell Wallace, PhD (Committee Member)

Subjects:

Acoustics; Industrial Engineering; Materials Science; Statistics

Keywords:

Rapid Solidification; Additive Manufacturing; Low cost metal 3D printing; Ultrasonics; Columnar Grain

Yerich, Andrew JDevelopment of an Artificial Nose for the Study of Nanomaterials Deposition in Nasal Olfactory Region
Master of Science, Miami University, 2017, Chemical, Paper & Biomedical Engineering
Engineered nanoparticles show great promise as a future medium for drug delivery due to their ability to transport great distances within the human body. Recent studies have shown that some nanoparticles may have the ability to diffuse to the central nervous system by means of the olfactory region of the nasal cavity. Although animal models and human simulations are available, the information they can provide is limited. In order to better test nanoparticles on this possible pathway, this study has created a more advanced respiratory device that incorporates a microfluidic device in a nasal cavity model to mimic the olfactory region through 3D modeling and printing. The unique geometry of the nasal cavity allows for the gathering of more realistic results. This unique respiratory device, in conjunction with an artificial lung apparatus, is able to accurately simulate a breathing human nasal cavity. During this study, the artificial nasal cavity was exposed to particles of varying sizes to determine the dosage reaching the olfactory region, which in turn can be used to determine which types of particles are most likely to travel this pathway. Results show similar trends to that of past studies: smaller nanoparticles are more effective at transporting to the olfactory region. While preliminary results are promising, further modifications to the setup are discussed that might better simulate an actual nasal cavity as well as to incorporate cell culture into the design.

Committee:

Lei Kerr, PhD (Advisor); Shashi Lalvani, PhD (Committee Member); Douglas Coffin, PhD (Committee Member)

Subjects:

Biomedical Engineering; Chemical Engineering

Keywords:

olfactory; nasal cavity; nose; nanoparticles; nanomaterials; drug delivery; 3D printing; model; in vitro; particle deposition; gold nanoparticles; neurological drug delivery; microfluidics; organ-on-chip; microfluidic devices

Keerthi, SandeepLow Velocity Impact and RF Response of 3D Printed Heterogeneous Structures
Master of Science in Mechanical Engineering (MSME), Wright State University, 2017, Mechanical Engineering
Three-dimensional (3D) printing, a form of Additive manufacturing (AM), is currently being explored to design materials or structures with required Electro-Mechanical-Physical properties. Microstrip patch antennas with a tunable radio-frequency (RF) response are a great candidate for 3D printing process. Due to the nature of extrusion based layered fabrication; the processed parts are of three-layer construction having inherent heterogeneity that affects structural and functional response. The purpose of this study is to identify the relationship between the anisotropy in dielectric properties of AM fabricated acrylonitrile butadiene styrene (ABS) substrates in the RF domain and resonant frequencies of associated patch antennas and also to identify the response of the antenna before and after a low velocity impact. In this study, ANSYS high frequency structure simulator (HFSS) is utilized to analyze RF response of patch antenna and compared with the experimental work. First, a model with dimensions of 50 mm x 50 mm x 5 mm is designed in Solidworks and three separate sets of samples are fabricated at three different machine preset fill densities using an extrusion based 3D printer LulzBot TAZ 5. The actual solid volume fraction of each set of samples is measured using a 3D X-ray computed tomography microscope. The printed materials appeared to exhibit anisotropy such that the thickness direction dielectric properties are different from the planar properties. The experimental resonant frequency for one fill-density is combined with ANSYS-HFSS simulation results to estimate the bulk dielectric constant of ABS and the equivalent dielectric properties in planar and thickness directions. The bulk dielectric properties are then used in HFSS models for other two fill densities and the simulated results appear to match reasonably well with experimental findings. The similar HFSS modeling scheme was adopted to understand the effect of material heterogeneity on RF response. In addition, a hybrid structure with dimensions of 50 mm x 50 mm x 20 mm is designed with the first 15 mm thickness being a cellular BCC structure and the other 5 mm being a solid cuboid. These samples are printed on an extrusion based 3D printer Stratasys uPrint using ABS. A patch antenna is embedded at the interface of the solid and the cellular structure. Both ABAQUS finite element modeling and experimental methods are used to understand the load-displacement and the energy absorption behavior of the hybrid structure under low velocity impact loadings. The hybrid structure is impacted on both sides to investigate the damage tolerance capabilities of embedded electronic components.

Committee:

Ahsan Mian, Ph.D. (Advisor); Raghavan Srinivasan, Ph.D. (Committee Member); Joy Gockel, Ph.D. (Committee Member)

Subjects:

Aerospace Engineering; Automotive Engineering; Design; Electrical Engineering; Mechanical Engineering; Mechanics; Plastics; Technology

Keywords:

Additive Manufacturing; AM; 3D Printing; Acrylonitrile Butadiene Styrene; ABS; Microstrip Patch Antenna; Porous; ANSYS-HFSS; ABAQUS-Explicit Dynamics; Hybrid Structure; Lattice Structure; BCC; RF applications; Low Velocity Impact; Dielectric material

Nimbalkar, Siddharth V3D PRINTED CHITOSAN: PEGDA SCAFFOLDS FOR AURICULAR CARTILAGE REGENERATION BY STEREOLITHOGRAPHY AT VISIBLE LIGHT RANGE
Master of Sciences (Engineering), Case Western Reserve University, 2017, Biomedical Engineering
Hydrogels allow chondrocytes to maintain their morphology and provides an ideal environment for the chondrocytes to produce cartilage. Hydrogels have been widely used in three- dimensional (3D) printing to create scaffold for tissue engineering. There are various methods in additive manufacturing however, for this study we have decided to use stereolithography because of its high accuracy. In this study, we created a new hybrid biocompatible resin using a combination of natural and synthetic polymers (chitosan and polyethylene glycol diacrylate (PEGDA), respectively) by varying feed-ratios and photo-initiator concentration. Ear-shaped hybrid scaffolds were fabricated by a stereolithographic method using a low cost commercially available 3D printer. Hybrid hydrogel mixture of chitosan (50–190 kDa) and PEGDA (575 Da) were mixed at different feed-ratios. The formulations that were made were ideal in terms of mechanical properties and cell viability. However, the lyophilizing the scaffold affected the porosity that resulted in uneven cell adhesion. Therefore, an alternative formulation of Chitosan and PEGDA mixture was created which subsequently improved the scaffold porosity by CAD printing of the scaffold. This is the first report of stereolithographic printing using a commercially available low cost 3D printer hybridizing cell adhesive properties of chitosan with mechanical robustness of PEGDA in scaffolds suitable for regenerative process of the cartilage.

Committee:

Ozan Akkus (Committee Chair); Dominique Durand (Committee Member); Eben Alsberg (Committee Member)

Subjects:

Biomedical Engineering; Biomedical Research

Keywords:

Stereolithography, 3D printing, Chitosan, PEGDA, Auricular cartilage, Tissue Engineering

Kunchala, PragnyaSlurry Jetting Printing of Ceramics with Nanoparticle Densifiers
Master of Science (MS), Ohio University, 2018, Mechanical Engineering (Engineering and Technology)
Additive manufacturing, though found to be an attractive alternative to make ceramics with complicated geometry, presents low mechanical properties due to high porosity. Literature showed introducing nanoparticle densifiers into the printed part as an effective way to improve its mechanical properties. However, focused investigation of the influence of variation in densifier content on the ceramic part properties is currently lacking in research pertaining to additive manufacturing. The current work addresses these issues in the additive manufacturing of ceramics by adding alumina nanoparticles (densifier) to the printing liquid. The slurry-jetted samples were characterized for density, porosity and compressive strength with increasing densifier content in the printing slurry. The presence of the nanoparticle densifiers had a marked effect on the physical and mechanical properties of the slurry-jetted samples. Bulk density of slurry-jetted samples increased by about 29.6% while porosity of cured parts decreased by about 35.7% with increasing densifier concentration from 0 - 15 wt.%. Additionally, compressive strength of the samples improved from 76 kPa to 641 kPa. Surface tension of the printing slurry decreased from 43.7 mN/m to 22.6 mN/m as the densifier concentration was increased from 0 - 15 wt.%. It was evident that the concentration of densifiers is a limiting factor as it decreases the penetration depth of printing slurry in the filler particles with decreasing surface tension.

Committee:

Keerti Kappagantula (Committee Chair); Greg Kremer (Committee Member); John Cotton (Committee Member)

Subjects:

Materials Science; Mechanical Engineering; Nanotechnology

Keywords:

3D Printing; slurry jetting; ceramics; nanoparticles; densifiers; infiltration; pore structure

Schomer, John JEmbedding fiber Bragg grating sensors through ultrasonic additive manufacturing
Master of Science, The Ohio State University, 2017, Mechanical Engineering
Fiber Bragg Grating (FBG) sensorsare optical fibers that detect in-situ strain through deviation of a reflected wavelength of light to detect in-situ strain. These sensors are immune to electromagnetic interference, and the inclusion of multiple FBGs on the same fiber allows for a seamlessly integrated sensing network. FBGs are attractive for embedded sensing in aerospace applications due to their small noninvasive size and prospect of constant, real-time nondestructive evaluation. FBGs are typically used in composite laminate type applications due to difficulties in building them into metallic structures. Additive manufacturing, also referred to as 3D printing, can allow for the inclusion of sensors inside of structural entities by the building of material around the sensor to be embedded. In this study, FBG sensors are embedded into aluminum 6061 via ultrasonic additive manufacturing (UAM), a rapid prototyping process that uses high power ultrasonic vibrations to weld similar and dissimilar metal foils together. UAM was chosen due to the desire to embed FBG sensors at low temperatures, a requirement that excludes other additive processes such as selective laser sintering or fusion deposition modeling. This study demonstrated the feasibility of embedding FBGs in aluminum 6061 via UAM. Further, the sensors were characterized in terms of birefringence losses, post embedding strain shifts, consolidation quality, and strain sensing performance. Sensors embedded into an ASTM test piece were compared against an exterior surface mounted foil strain gage at both room and elevated temperatures using cyclic tensile tests. The effects of metal embedment at temperatures above the melting point of the protective coating (160 degrees Celsius) of the FBG sensors were explored, and the hermetic sealing of the fiber within the metal matrix was used to eplain the coating survival. In-situ FBG sensors were also used to monitor the UAM process itself. Lastly, an example application was both modeled using finite element analysis to identify areas where FBG sensors could be placed, and then built with an embedded FBG sensor.

Committee:

Marcelo Dapino (Advisor); Mo-How Shen (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

Fiber Bragg Grating, Ultrasonic Additive Manufacturing, Structural Health Monitoring, 3D Printing, Fiber Optic

Jeong, Kyoung HoDesign, Fabrication and Measurement of Millimeter Fresnel Lens and Helical Antenna using Additive Manufacturing
Master of Science, The Ohio State University, 2017, Electrical and Computer Engineering
Design, simulation, fabrication and measurement results of 3D-printed Fresnel lens and helical antenna are presented. Because the real and imaginary permittivity of the 3D-printed material (Polylactic Acid) at the frequencies of interest were unknown, we have measured these properties using time-domain spectroscopy as well as impedance/material analyzer. Full-wave simulation was used to design and optimize the realized gain of the lens and helical antenna. These devices were later on fabricated using fused deposition modeling and stereolithography, respectively. The gain pattern measurements were then performed in the anechoic chamber. Measurement results showed that the lens could achieve a gain improvement of 8-9 dB at 30 GHz. Furthermore, a 3D-printed helical antenna with suspended microstrip was shown to achieve a gain of 14 dB and half-power beam width of 30°, which closely agreed with the simulated data. By designing, fabricating and characterizing the two aforementioned examples, the limitation and challenges associated with additive manufacturing for antenna applications were studied. Moreover, our study will advance realization of antenna structures, specifically in the millimeter wave band.

Committee:

Nima Ghalichechian (Advisor); Wladimiro Villarroel (Committee Member)

Subjects:

Electrical Engineering; Engineering

Keywords:

Additive manufacturing, 3D printing, Helical antenna, Fresnel lens

Ren, XiaoranA Wearable Fitness Device System for Multiple Biological Information Data Acquisition for Physically Active Persons
MS, University of Cincinnati, 2017, Engineering and Applied Science: Electrical Engineering
With the increasing interest in wearable fitness devices, there is an increasing interest in monitoring techniques that can quantify a physically active person’s pulse, blood oxygen saturation level and fluid loss rate. This thesis focuses on designing and implementing several different modules that are critical to wearable fitness devices including: power management system, communication system, and sensor arrays. The approach that has been taken is putting together commercial modules and developed modules along with prototype sensors to form a device that proves the functionality concept of a next generation wearable fitness device. In the power management system, there are designed circuit to convert power from battery, USB cable and commercial inductive charging module to targeted voltages for the rest of the system. A micro-controller collects data from sensor arrays, including a developed module for pulse-OX, and a prototype sensor for sweat rate monitoring. After collection of data, the microcontroller processes the acquired data and sends them via Bluetooth to PC software or mobile application. From experiment results, it is shown that the device is able to measure the pulse and blood oxygen saturation level of a physical active person. It also has proven that the concept of using a screen-printed based chip to monitor the fluid loss rate of a physical active person. It is verified that with a combination of pulse, blood oxygen saturation level and body fluid loss monitoring, a wearable fitness device is possible. And along with the 3D printing technology and electro-chemistry technology, future development could convert this proof-of-concept prototype into a commercial device.

Committee:

Fred Beyette, Ph.D. (Committee Chair); Wen-Ben Jone, Ph.D. (Committee Member); Carla Purdy, Ph.D. (Committee Member)

Subjects:

Engineering

Keywords:

Fitness Device;Sweat Monitoring;Embedded System;Pulse Oximetry;3D Printing;Inductive Charging

Wade, Mary EEngineering of Elastomeric Biomaterials and Biomimicry of Extracellular Matrix for Soft Tissue Regeneration
Doctor of Philosophy, University of Akron, 2016, Integrated Bioscience
Discoveries of new synthetic polymeric materials have become increasingly important in the field of biomedicine. Recent advancements in bio-functionalization strategies have led to innovation of biomimetic materials that can enhance tissue regeneration. Poly(ester urea)s are one unique set of materials comprised of amino acids and diols that are able to achieve tunable mechanical and degradation properties for a variety of tissue engineering applications. These materials can be functionalized with peptides utilizing an assortment of strategies in order to enhance cellular and tissue interactions. One alternative functionalization strategy under current investigation is combining decellularized extracellular matrix with poly(ester urea)s using engineering approaches such as electrospinning, melt-spinning, and 3D-printing. Our research into these techniques has provided interesting insights into the effects of processing on nanostructured scaffolds, and how molecular and scaffold structure can be tailored to overcome processing obstacles. We have also recently discovered a new series of elastomeric materials inspired by the chemical structure of rubber. These new polymers also exhibit tunable mechanical and degradation properties. We have tested these elastomers in vitro and in vivo and observed excellent cellular and tissue responses. Elastomers containing a degradable monomer in every copolymer repeat unit were capable of degrading within a period of 4 months in vivo while allowing for significant tissue infiltration and matrix regeneration. These two examples support the use of biomimicry for the design of novel materials, from molecular synthetic strategies to macromolecular scaffold design, and similar approaches will play a critical role in furthering the development of biomaterials for tissue regeneration.

Committee:

Matthew Becker (Advisor); Rebecca Willits (Committee Chair); Amy Milsted (Committee Member); Ge Zhang (Committee Member); Darrell Reneker (Committee Member)

Subjects:

Biology; Biomechanics; Biomedical Engineering; Biomedical Research; Cellular Biology; Chemistry; Polymer Chemistry; Polymers

Keywords:

elastomer; electrospinning; melt spinning; 3D printing; sterilization; sewing; extracellular matrix; biomimicry; tissue regeneration; inflammation; biomaterial

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