Publications

Transition Metal Dichalcogenides (TMDs) are a unique class of materials that exhibit attractive electrical and optical properties which have generated significant interest for applications in microelectronics, optoelectronics, energy storage, and sensing. Considering the potential of these materials to impact such applications, it is crucial to develop a reliable and scalable synthesis process that is compatible with modern industrial manufacturing methods. Metal–organic chemical vapor deposition (MOCVD) offers an ideal solution to produce TMDs, due to its compatibility with large-scale production, precise layer control, and high material purity. Optimization of MOCVD protocols is necessary for effective TMD synthesis and integration into mainstream technologies. Additionally, improvements in metrology are necessary to measure the quality of the fabricated samples more accurately. In this work, we study MOCVD of wafer-scale molybdenum disulfide (MoS2) utilizing two common chalcogen precursors, H2S and DTBS. We then develop a metrology platform for wafer scale samples quality assessment. For this, the coalesced films were characterized using Raman spectroscopy, atomic force microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Kelvin probe force microscopy. We then correlate the structural analysis of these grown films with electrical performance by using aerosol jet printing to fabricate van der Pauw test structures and assess sheet resistance.

Flexible and printed electronics have become increasingly popular as they make possible the production of flexible, low-cost, multifunction devices that are unachievable through traditional manufacturing methods. The printed films are significantly impacted and thus limited by the existing ink production process. Herein, an alternate technique of generating high-quality titanium dioxide (TiO2) nanoparticle ink compatible with aerosol jet printing using laser ablation synthesis in solution (LASiS) is showcased. Dynamic light scattering data and transmission electron microscopy confirm the particle size distribution. UV–vis measurements are performed, and the Beer–Lambert relationship is used to determine the concentration of the generated ink. The inks generated at two different repetition rates are compared: 200 kHz and 1 MHz. X-Ray diffraction analysis of the aerosol jet printed thin film post-thermal sintering confirms the grain size and phase purity of the printed thin films. This work demonstrates the effectiveness of the LASiS technique in producing printable nanoparticle inks with little-to-no postprocessing.

Inflatable structures, promising for future deep space exploration missions, are vulnerable to damage from micrometeoroid and orbital debris impacts. Polyvinylidene fluoride-trifluoroethylene (PVDF-trFE) is a flexible, biocompatible, and chemical-resistant material capable of detecting impact forces due to its piezoelectric properties. This study used a state-of-the-art material extrusion system that has been validated for in-space manufacturing, to facilitate fast-prototyping of consistent and uniform PVDF-trFE films. By systematically investigating ink synthesis, printer settings, and post-processing conditions, this research established a comprehensive understanding of the process-structure-property relationship of printed PVDF-trFE. Consequently, this study consistently achieved the printing of PVDF-trFE films with a thickness of around 40 µm, accompanied by an impressive piezoelectric coefficient of up to 25 pC N−1. Additionally, an all-printed dynamic force sensor, featuring a sensitivity of 1.18 V N−1, was produced by mix printing commercial electrically-conductive silver inks with the customized PVDF-trFE inks. This pioneering on-demand fabrication technique for PVDF-trFE films empowers future astronauts to design and manufacture piezoelectric sensors while in space, thereby significantly enhancing the affordability and sustainability of deep space exploration missions.

In-pile instrumentation is critical for advancing operations and materials discovery in the nuclear industry. Ensuring optimal performance of sensors in high temperatures is the first step in demonstrating their viability in the harsh in-pile environment. This work demonstrates the high temperature capabilities of a line heat source and measurement technique previously shown to extract thermal conductivity of nuclear fuel sized samples within a laboratory environment at room temperature. This method uses a hybrid AC/DC measurement technique to obtain rapid measurements of the temperature dependent voltage change of a heater wire, which also acts as a resistance thermometer. Once the temperature profile of the heating element is extracted it is matched to a multilayered analytical model to determine the thermal conductivity of the sample. Measurements are conducted over a range of temperatures to extract the thermal conductivity as a function of temperature for 10 mm diameter 6061 aluminum samples. Each measurement had a coefficient of correlation (R2) value higher than 0.995 when matched to its corresponding analytical model. The thermal diffusivity values for each temperature are also identified and reported. Microstructure analysis was also conducted to further characterize the material measured.

Traditional potentiostats, while essential for electrochemical research, have often been bulky and immobile, presenting logistical challenges for laboratories requiring their use. This has prompted the development of smaller, more portable variants, offering greater convenience and flexibility. Particularly intriguing are low-cost potentiostat devices made from microcontrollers equipped with Bluetooth or short-range connectivity, facilitating seamless data transmission to mobile devices, servers, or other acquisition systems. In our laboratory, we are actively engaged in the rapid prototyping of such low-cost potentiostat devices, exploring their potential applications in conjunction with flexible electronics. By leveraging these advancements, we aim to enhance the accessibility and versatility of electrochemical research, paving the way for innovative solutions in various fields.