Doctor of Philosophy, The Ohio State University, 2009, Biomedical Engineering

The demand for flexible substrates in the electronics industry and medicine has highlighted the importance of applicable printing techniques on these materials. Neural prosthetics interfacing with soft tissues and tight packaging requirements in the high-frequency electronics field require application-specific fabrication methodologies for printing conductors on or embedded in flexible substrates. The purpose of this dissertation is to introduce novel fabrication techniques for printing metal patterns on silicone elastomers. In pursuing this goal, two applications in the biomedical and antennas fields are given. These applications require printing of metals on silicone elastomers and the requirements of these applications are met with application-specific microfabrication processes. The initial project involves printing microwave structures on PDMS-ceramic composites. These structures include transmission lines, a patch antenna and a feeding pattern for a GPS antenna. The second work requires the fabrication of a microelectrode array for recording neural signals from the brain cortex surface. Microfabrication techniques have been developed for the device fabrications. In the first application, a novel technique for direct printing of patterned conducting geometries on silicone-based, flexible polymer composites is presented. Specifically, micro-texturing is applied on the polymer composite surface followed by evaporation of a buffer titanium layer and a seed layer of copper. Electroplating is also applied as a final step to increase conductor layer thickness to accommodate polymer layer bending while maintaining good RF conductivity. The printed examples include 5 mm wide copper microstrip lines on polymer composite substrates. These printed microstrip lines demonstrated very low sheet resistivity of 0.1 ohm per square for frequencies up to several GHz. They were also shown to maintain low resistance during large bending deformations. To investigate RF performanc (open full item for complete abstract)

Committee: Derek Hansford (Advisor); Yi Zhao (Other); Jessica Winter (Other) Subjects: Engineering

Master of Science, The Ohio State University, 1961, Graduate School

Committee: Not Provided (Other) Subjects:

MS, University of Cincinnati, 2024, Engineering and Applied Science: Mechanical Engineering

Electroplating is a technique used to coat components with a protective layer of metal which has better resistance against wear and tear, corrosion, surface finish, and overall performance compared to the substrate material. Electroplating with zinc, zinc-nickel, or cadmium is widely used to prevent corrosion and increase the product's lifespan. Zinc-nickel alloy electroplating is a cost-effective and non-toxic alternative to other plating methods and is therefore preferred over cadmium coating. However, since zinc-nickel is a bi-metal alloy, the electroplating process is complex and affects the phase, structure, and surface of the plating. The properties of the plating rely heavily on the working conditions of the electroplating process and on the electrolyte. The composition of the electrolyte, applied voltage or current, time required for electroplating, and mass transport of ions in the electrolyte are a few of the many parameters that affect the plating. The characteristics of the workpiece, like surface finish, surface treatment methods, or machining process, also impact the properties of the plating. As the overall performance of the plated component depends on the microstructure and composition of the plating, it is necessary to understand and evaluate the plating to predict the product's performance successfully at the macro level. The aim of this research is to determine the electrolyte composition that provides good surface properties and the desired nickel content and evaluate the corrosion performance of the plating. The performance of the electrolyte is assessed by electroplating workpieces using different fluid circulation techniques like stationary, vibration-assisted, and stirring-assisted. In addition, the workpiece's surface finish and the surface treatment sequence were varied by conducting ultrasonic nano surface modification and, before, after, or both, electroplating these workpieces to determine if the electrolyte would perform equally well. (open full item for complete abstract)

Committee: Murali Sundaram Ph.D. (Committee Chair); Dinc Erdeniz Ph.D. (Committee Member); Jing Shi Ph.D. (Committee Member) Subjects: Mechanical Engineering

MS, University of Cincinnati, 2023, Engineering and Applied Science: Mechanical Engineering

Ultrasonic Nanocrystal Surface Modification (UNSM) is a relatively new surface modification technique caused by severe plastic deformation,. UNSM involves scanning a CNC-controlled Tungsten Carbide ball tip across the surface of the specimen whilst it vibrates at an ultrasonic frequency backed by a static load. The ultrasonic vibration backed by the static load coupled with the scanning action have an overall effect that can be considered analogous to a hybrid of micro-cold forging and burnishing. Numerous studies have been undertaken toward understanding the underlying principles governing the outcome of the process, however, a comprehensive investigation into the effects of different processing parameters on the surface properties of the processed specimen has been missing from the literature. The objective of this study was to perform a comprehensive investigation of the effects of different processing parameters of UNSM on the surface properties of 300M steel, a material that is widely used for numerous applications such as aircraft landing gears and high-performance drive shafts. Experiments were performed using combinations of the following three processing parameters: scanning speed, scanning interval, and static load. The resulting surfaces were evaluated for surface hardness, roughness, wettability, appearance, and residual stresses. After analyzing the results, it was observed that the sliding action of the scanning motion caused trenches, visible under a microscope, to form on the surface of the specimen that was found to be one scanning interval apart. It was found that as the scanning speed is decreased the micro-cold forging action of the vibratory motion becomes the dominant governing mechanism of the process and the surface roughness increases as a result of decreasing scanning speed. The increase in static load was observed to intensify the peening action of the vibratory motion of the tungsten carbide tip resulting in surface damage, visible (open full item for complete abstract)

Committee: Murali Sundaram Ph.D. (Committee Chair); Manish Kumar Ph.D. (Committee Member); Dinc Erdeniz Ph.D. (Committee Member) Subjects: Mechanical Engineering

Master of Science in Engineering, Youngstown State University, 2022, Department of Civil/Environmental and Chemical Engineering

Additive manufacturing (AM) commonly referred to as 3D printing is a method of manufacturing three-dimensional parts in a layer-by-layer fashion. Common materials used in this process are polymers, metals, and ceramics. Nowadays, AM is utilized for more than just traditional structures - it is used to fabricate and create nontraditional designs. Additive manufacturing is associated with various industrial manufacturing processes and innovations including maintenance, repairs, and product design. Among the different applications of this process, the production of 3D printed morphing systems and parts for batteries represents an attractive approach for yielding high-performance structures. Non-metallic morphing components are commonly constituted by shape memory polymers (SMPs), which are actuating materials that can respond to thermal, electrical, or chemical stimuli. Here, SMPs were constructed by incorporating two different blends of photopolymer resins in a Vat Photopolymerization process. The printed SMPs were subsequently electroplated with copper to yield a conductive morphing structure for applications such as sensors, actuating systems, and functional antennas. The present work investigated the adaptability and functionality of the copper-plated 3D printed parts as morphing antennas capable of providing a multi-radio frequency. Additionally, this research program investigated the production and performance of 3D printed LiFePO4 parts via Vat Photo Polymerization to be used as electrodes on additively manufactured energy storage devices. This effort represents a novel approach to further expanding the production of customized batteries.

Committee: Pedro Cortes PhD (Advisor); Vamsi Borra PhD (Committee Member); Frank Li PhD (Committee Member) Subjects: Aerospace Materials; Chemical Engineering; Materials Science; Polymers

Doctor of Philosophy, Case Western Reserve University, 2020, Chemical Engineering

High-energy density batteries are essential for powering future electric vehicles (EVs) and electric aircraft. These technologies are limited by the capacity of their batteries. Enabling high-specific energy batteries could make longer-range electric vehicles and electric aircraft a reality. The Li-metal anode offers the highest theoretical specific energy among practically available anode materials. However, secondary Li-metal anodes experience capacity loss and safety hazards caused by the growth of dendrites on the anode surface during charging. After four decades of research on Li-metal batteries, rechargeable Li-metal anodes that do not evolve dendrites are still not commercially available. Understanding the physical causes and mechanisms of dendritic Li electrodeposition, in order to develop commercial Li-metal batteries, motivates the present work. It is shown herein that solid-state transport limitations within a dynamic solid electrolyte interphase (SEI) are dominant in controlling the time when Li dendrites first form. Chronopotentiometry and optical imaging provide experimental observations for when dendrites first appear on a Li electrode. Dendrite onset time is shown to increase with increasing temperature and decrease with increasing current density and initial SEI thickness. These phenomena are shown to be due to the onset of diffusion limitations brought on by a thickening SEI. Electrochemical impedance spectroscopy (EIS) provides evidence for SEI growth and enables estimation of the SEI growth rates during Li electrodeposition. These experiments guide the development of an analytical model that explains mechanistically how transport limitations within the SEI control the onset time of dendrite growth during Li electrodeposition. The model also provides predictions of Li dendrite onset times. These predictions agree qualitatively with the observed effects of current density, initial SEI thickness, temperature, and pulsing. Finally, it is shown th (open full item for complete abstract)

Committee: Rohan Akolkar PhD (Advisor); Uziel Landau PhD (Committee Member); Donald Feke PhD (Committee Member); Alp Sehirlioglu PhD (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, Case Western Reserve University, 2014, Chemical Engineering

All semiconductor devices incorporate metallic interconnects, which provide the electrical network within the device. The interconnects are fabricated by electroplating copper from electrolytes containing special additives, enabling bottom-up fill of the vias and trenches. The study herein focuses on identifying new additives screening techniques and characterizing the associated process parameters through systematic experimental investigation and analytical modeling. A new improved test for characterizing the efficacy of the additives system has been developed and validated as a replacement for the classical injection technique. Results of the test have been implemented in a quantitative model indicating the expected gap-fill in wafer plating of small features. Additionally, a computer-based model of the additives co-injection test has been developed. This model accounts for the flow field external to the features and characterizes the actual wafer plating process more precisely than previous models. Fitting experimental data to the model provides more accurate estimates of process parameters, including additive adsorption rates, than heretofore possible. Several process parameters were characterized. Temperature was found to affect additives (polyethylene glycol [PEG] serving as a suppressor and bis(3-sulfopropyl) disulfide [SPS] serving as anti-suppressor) activity. An optimal process temperature of ~30oC was identified, where the SPS depolarized electrode reverts to pure copper plating kinetics and maximal polarization is achieved. The effects of pH, in the range 0.5-2, on the deposition kinetics were found to be minor; however, corresponding effects on seed stability were substantial, with improved seed stability at the higher pH. Substituting chloride with bromide provided slight improvement in the deposition kinetics. With bromide, displacement of the suppressor by the anti-suppressor was slow compared to displacement in the presence of chlori (open full item for complete abstract)

Committee: Uziel Landau (Advisor); Rohan Akolkar (Committee Member); Heidi Martin (Committee Member); Daniel Scherson (Committee Member); Robert Preisser (Committee Member) Subjects: Chemical Engineering

MS, University of Cincinnati, 2012, Engineering and Applied Science: Mechanical Engineering

The ability to offer multiple functionalities with minimal space, material and energy utilization has led to increase in demand for micro products with sizes ranging from tens of micrometers to few millimeters. Micro system products have several applications in biotechnology, electronics, optics, medicine, avionics, automotive and aerospace industries. Superior mechanical and physical properties offered by advanced engineering materials comprising metals, ceramics and fiber-reinforced composites have led to their increased usage in micro system products such as X-ray lithography masks, micro-fluidic devices, micro-scale heat sinks, biomedical instruments, and miniaturized mechanical devices like actuators, gears and motors. Advanced engineering materials used in these microsystems are often hard, brittle, and electrically nonconductive and pose micromachinability challenges. Micromachining with sub-micron cutting depth by micro-sized abrasive tools is capable of deterministic material removal with minimal sub-surface damage in advanced composites and ceramics. To achieve this, it is essential to fabricate precise abrasive microtools to enable abrasive micromachining. In this research work, an experimental system has been designed and built in-house for fabrication of abrasive microtools using the principles of pulse-current electrodeposition. Abrasive microtools of diameter 300 ¿¿¿¿m embedded with 2-4 ¿¿¿¿m diamond grit have been produced using this system. A mathematical model has been developed and experimentally verified to predict the weight percent of micro abrasive particles incorporated in binder matrix, for a given set of pulse-plating conditions. Designed experimental studies have been conducted using Taguchi method to understand the effect of process parameters on proportion of abrasives embedded during the tool making process. These studies indicated that shorter pulse durations at higher duty factors result in nominal extent of abrasive incorporation, at (open full item for complete abstract)

Committee: Murali Sundaram (Committee Chair); Sundararaman Anand (Committee Member); Jay Kim (Committee Member) Subjects: Mechanical Engineering