Master of Science (MS), Wright State University, 2011, Chemistry

Solid oxide fuel cell (SOFC) technology has attracted great attention due to advantages such as low emissions and high efficiency. In this work, solid oxide fuel cells were fabricated by incorporating functional layers deposited by a novel aerosol jet® printing method. The buffer and cathode layers were printed from gadolinium doped ceria (Ce0.9Gd0.1)O1.95 (CGO) and La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) inks, respectively. The CGO layer was deposited on the sintered electrolyte and then LSCF was subsequently deposited onto the CGO layer. The polarization curves showed a 19% improvement in current density using LSCF as the cathode instead of LSM. Cathode grain size was shown to change by 85% over the sintering temperatures examined. Lastly, the effect that ethyl cellulose additive had on the resulting cathode was determined. It was discovered that the porosity of the microstructure was not correlated to the additive's molecular weight. The actual causes of the cathode porosity may be the order of polymer branching or the ethoxy content of the ethyl cellulose.

Committee: Eric Fossum PhD (Advisor); David Grossie PhD (Committee Chair); Rachel Aga PhD (Committee Chair) Subjects: Chemistry

Master of Science in Mechanical Engineering (MSME), Wright State University, 2024, Mechanical Engineering

Heterogeneous integration (HI) is currently being investigated to maintain the pace of technological progress in the electronics industry. With the recent acceleration witnessed in additive manufacturing (AM) technology, interest has been expressed in introducing aerosol jet (AJ) printing to the fabrication process for sensors and electronic packages. Integrating AM technology in these areas promises design flexibility and minimal material waste. Three AJ printed applications investigated in this work include strain sensors, electrical interconnects, and metal embedded chip assemblies. Before moving forward with the use of AJ printing in these applications, it is necessary to evaluate their performance under standard mechanical testing. This work aims to assess the mechanical reliability of devices and interconnects which are manufactured using hybridized AJ printing techniques. The devices considered for this research include three passivated strain gauges, three non-passivated strain gauges, 28 electrical interconnects, and three additive MECA packages. The mechanical reliability of samples are assessed by subjecting the samples to a variety of standardized tests including vibration, shock, and thermal loading while tracking their performance.

Committee: Ahsan Mian Ph.D. (Advisor); Carrie M. Bartsch Ph.D. (Committee Member); Daniel Young Ph.D. (Committee Member) Subjects: Engineering; Mechanical Engineering

Master of Sciences (Engineering), Case Western Reserve University, 2024, Materials Science and Engineering

Aerosol jet printing (AJP) offers a unique solution to fabrication challenges for microelectronic devices due to its microscopic feature resolution, rapid prototyping capabilities, and ability to print on curved surfaces. However, AJP is challenged by a complex set of interrelated process parameters which must be carefully adjusted to achieve desired print properties. A series of studies were conducted to investigate the effects of AJP parameters on properties of silver nanoparticle ink flexible electronics, and to define an optimized set of parameters to achieve desired performance metrics. Specimens were characterized via optical microscopy, profilometry, electrical testing, static bend testing, and focused ion beam sectioning. It was found that silver nanoparticle ink retained chemical and particle size properties over a period of ~25 weeks. The effects of sintering parameters were investigated and it was determined that 175 °C marks a threshold sintering temperature below which prints did not conduct, but above, print conductance increased and microstructure showed densification and grain growth. A 65°C platen temperature was found to mitigate both spreading and excessive drying of ink. The effects of individual AJP process parameters on deposition thickness and conductance were evaluated. Finally, an orthogonal array optimization study was conducted to arrive upon a set of optimized printing parameters including aerosol and sheath gas flow, atomizer voltage, print speed, and platen temperature. Findings can be applicable to future works seeking to hasten the adaptation of aerosol jet printing to specific applications.

Committee: Janet Gbur (Committee Chair); James McGuffin-Cawley (Committee Member); John Lewandowski (Committee Member) Subjects: Biomedical Engineering; Electrical Engineering; Materials Science; Nanotechnology

Master of Science in Materials Science and Engineering (MSMSE), Wright State University, 2023, Materials Science and Engineering

Electronics in different applications, such as in medical imaging devices, radar systems, communication transmitters, and optical drives, often require various power and signal lines to be integrated at board level. In such cases, different lines may cross over one another in three-dimensional space for efficient electronic integration. Crossovers are usually achieved by adding additional layers to a PCB. However, these additional layers increase the cost, weight, and complexity of the component. By creating a process and structure to offer board-level heterogenous integration, these factors may be reduced. RF-DC crossovers were designed and additively manufactured using an aerosol jet printer. Benzocyclobutene (BCB), a thermally curable dielectric material, and Norland Electronic Adhesive 121 (NEA), a UV curable dielectric ink, were printed as crossover materials on boards containing an RF transmission line. Electroninks 615 (EI-615), a conductive silver ink, was printed on the crossover's surface to complete the DC circuit trace. Two different toolpath designs were explored to serve for the digital printing of the crossover structure. A network analyzer was used to measure the scattering parameters (S12 and S21) across the RF transmission line in X-band (8-12 GHz). A thermal camera was used to capture the heat spread across the crossover region. The printed ramp design resulted in a more gradual slope as expected, requiring a single print of the conductive trace while the steep pad design required tilting of the crossover and multiple printing sessions. The NEA 121 and BCB showed no significant changes in the S21 parameter as DC power increased; however, slight coupling occurred in both. The largest S21 difference recorded at 10 GHz was 0.339 dB. The BCB crossovers exhibited higher power handling than the NEA 121 crossovers, reaching up to 6.93 W. The maximum breakdown temperature occurred at 273.0°C in the NEA 121 and at 248.6°C in the BCB crossovers.

Committee: Ahsan Mian Ph.D. (Advisor); Daniel Young Ph.D. (Committee Member); Emily Heckman Ph.D. (Committee Member) Subjects: Electrical Engineering; Engineering; Materials Science

Master of Science in Engineering, Youngstown State University, 2023, Department of Electrical and Computer Engineering

Design and additive manufacturing of four different antennas that operate at microwave frequency is proposed. The designs were prototyped on flexible FR4 substrates to make them suitable for wearable sensors and biomedical applications. Contact and non-contact printing methods for antenna fabrication using screen printing and aerosol jet printing (AJP), respectively, were extensively studied as part of this research. Ansys High Frequency Structural Simulator (HFSS) was used to design and simulate the antenna characteristics. Nanoparticle silver ink, of ~10nm size, was used to fabricate antennas under AJP method. In addition, a screen-printing approach using copper paste was used to fabricate antennas. A vector network analyzer (VNA) was used to experimentally verify the nature of fabricated samples. The reflection coefficient (S11) and radiation patterns for the simulated design and fabricated samples were found to align closely. A return loss of -10 dB was achieved for the wide range of operating frequency. This demonstrates the effectiveness of the proposed antennas. Compact sizing, simplicity of manufacturing, a larger impedance spectrum, simple design, and high performance are some of the major advantages of the proposed additive manufacturing method.

Committee: Vamsi Borra PhD (Advisor); Pedro Cortes PhD (Committee Member); Srikanth Itapu PhD (Committee Member); Ghassan Salim (Committee Member) Subjects: Electrical Engineering; Electromagnetics; Materials Science

Doctor of Philosophy (Ph.D.), Bowling Green State University, 2019, Photochemical Sciences

This dissertation work is focused on development of zinc oxide (ZnO) thin films by atomic layer deposition (ALD) and sol-gel processes and investigating its optoelectronic properties and potential applications in flexible electronics. Through ALD efforts, a unique doping method was developed to incorporate In3+ and Ga3+ donors in ZnO at 250°C. The ALD process allowed us to deposit individual layers of In and Ga precursors, sandwiched between many layers of ZnO. The result is a 160-nm indiumgallium- doped ZnO (IGZO) transparent conductive oxide (TCO), with a sheet resistance of 60.9 Ω·sq-1 and percent transmittance > 93.8% at 550 nm, and figure of merit Φ = 8.66 × 10-3 Ω-1. IGZO is shown to be amorphous or polycrystalline in nature, depending on the substrate, but all IGZO thin films exhibit a low resistivity ρ (≤1.10 × 10-3 Ω·cm), high carrier concentration η (≥2.30 × 1020 cm-3), and high mobility μ (≥15.3 cm²/V·s). IGZO was found to be a fully degenerate semiconductor. Compared to gallium-doped ZnO (GZO), it appears that In3+ is responsible for the improved polycrystalline growth and increased grain size. Based on these results IGZO is a promising replacement for the industry-standard indium tin oxide (ITO) for TCO applications. A sol-gel approach was used to deposit ZnO and IGZO layers onto a variety of flexible and transparent substrates using spin coating, inkjet printing (IJP), and aerosol jet printing (AJP) tools. In and Ga were introduced as co-dopants in solution and improved conductivity and polycrystalline growth. The polycrystallinity of ZnO improves with temperature from 200– 400°C and is dependent on the substrate. Both ZnO and IGZO thin films exhibit a decrease in resistivity upon UV exposure (103–106 Ω·cm). Increasing the light intensity further shows a nonlinear behavior. This effect is attributed to UV light adsorption and oxygen desorption. Upon bending the substrate at a 4 mm radius of curvature, the photoconductive response (open full item for complete abstract)

Committee: Farida Selim Ph. D. (Advisor); Brent Archer Ph. D. (Other); Malcolm Forbes Ph. D. (Committee Member); Emily Heckman Ph. D. (Committee Member); Alexey Zayak Ph. D. (Committee Member) Subjects: Physics

Master of Science (MS), Wright State University, 2018, Chemistry

Additive manufacturing is a rapidly expanding field of research. Additive manufacturing and direct writing techniques used to fabricate printed electronics will enable the continued miniaturization of electronic devices as new materials and techniques are developed. In this study SU-8, a dielectric material commonly used in traditional fabrication, is adapted for use by aerosol jet printing, an additive manufacturing technique. Printing parameters are established and the effect of UV exposure and post-exposure baking (PEB) on the thickness and dielectric properties of the material are determined by profilometer and LCR measurements. Increasing the UV exposure is observed to lower the dielectric constant of the printed films. Increasing the temperature of the PEB is observed to lower the dielectric constant of SU-8 films, but increasing the PEB time is not observed to have any impact on the dielectric constant. The films produced by printing have similar dielectric properties compared to those fabricated by spin coating. The printing of SU-8 and carbon nanotubes (CNT) was utilized to fabricate an all-printed nanocomposite material. In addition, printed SU-8 capacitors are evaluated for their frequency dependence. Finally, the further improvement of SU-8 printing parameters for nanocomposite fabrication in future work is started.

Committee: Rachel Aga Ph.D. (Advisor); Emily Heckman Ph.D. (Advisor); David Dolson Ph.D. (Committee Member); Ioana Sizemore Ph.D. (Committee Member) Subjects: Chemistry

Master of Sciences (Engineering), Case Western Reserve University, 2018, EMC - Mechanical Engineering

Poly(ethylene oxide)-LiTf-Al2O3 and Poly(ethylene oxide)-LiTf-Li1.5 Al0.5Ge1.5(PO4)3 composite solid electrolyte films for use in Lithium ion batteries were fabricated by aerosol jet deposition. The composite electrolytes were synthesized using three distinctly sized Al2O3 nanoparticles with specific surface areas of 111, 9.08 and 6.02 m2/g respectively, while the LAGP particles had a specific surface area of 7.25 m2/g. Each composite electrolyte was synthesized with EO:Li equal to 16:1, while the volume proportion of added ceramic was varied from 0 to 18% in relation to the PEO-based polymer matrix. In general, electrolyte films containing particles with high surface area and loaded at low volume fractions had greater conductivities. For example, composite electrolytes containing Al2O3 (111 m2/g) at a proportion of 3.5 vol.% showed the highest ionic conductivity of 3.99×10-5 Scm-1 at 30oC. Electrolytes containing LAGP particles generally performed better than films containing comparable sized Al2O3, such as the electrolyte containing LAGP (7.25 m2/g) at a proportion of 3.5 vol.% which obtained the second highest ionic conductivity of 2.24×10-5 Scm-1 at 30oC. Both electrolytes showed ionic conductivities approximately two orders of magnitude higher than the PEO-based electrolyte with no ceramic filler.

Committee: Vikas Prakash Dr. (Committee Chair); Thomas Howell Dr. (Advisor); Dan Lacks Dr. (Committee Member); Clare Rimnac Dr. (Committee Member) Subjects: Chemical Engineering; Electrical Engineering; Energy; Materials Science; Mechanical Engineering; Polymer Chemistry; Polymers

Master of Science, The Ohio State University, 2005, Mechanical Engineering

The dynamics and microphysical mechanisms effecting aerosols in a turbulent jet were considered. The expressions available for the collision kernels in the current literature were combined in a new way, in an attempt to capture the involved physics and their effects more completely. After introducing the relevant consepts and mechanisms, the governing equations and the numerical models approximating them were discussed. Using the models the time evolution of an aerosol in homogeneous space was investigated for various turbulence conditions. Then the time dependent models were modified to approximate a turbulent jet at steady state, by assuming the aerosol to only vary along the axial direction. A two dimensional steady state model was constructed to investigate the suitability of the new collision kernels and their implications in more realistic models. After discussion of the significant findings, suggestions for the direction for continued research were made.

Committee: Seppo Korpela (Advisor) Subjects: Engineering, Mechanical