(6da) Electrochemical Plasma Reactions and Supersonic Printing: A Route Towards Multi-Component Materials Discovery and Scalable Device Manufacturing

I am interested in the complex interactions between multi-component materials systems through heat-, light- and charge-transfer reactions. Flames and plasmas present these elements in the form of phonons, photons and reactive charges. These reactions are clean from chemical interferences and can be created under controlled and atmospheric-pressure conditions. They provide the ideal media for studying fundamental chemical reactions. I will incorporate in situ and ex situ techniques including velocimetry, mobility analyses, spectroscopy and materials characterization to understand the underlying chemical reaction phenomena. The fundamental understanding of these reactions at the electrochemical-interfaces is the key to the development of a sustainable and energy efficient future.

My current research scope has shaped my interests in materials discovery and stoichiometry-controlled multi-component nanoparticle synthesis. In particular, doped complex oxides and their thin films are promising candidates for energy efficient devices. Existing additive manufacturing techniques are unable to deposit high temperature materials on soft and temperature-susceptible substrates such as polymers. Researchers usually rely on substrate-specific complex chemical techniques such as self-assembly for the deposition of complex oxides, carbides and nitrides. Supersonic aerosol impaction can deposit a wide variety nano- to micro- sized powders and is not limited to factors such as viscosities and surfactants that otherwise plague conventional printing techniques. Using my expertise on plasmas, flames, and supersonic aerosol printing, I look forward to opportunities to discover new materials, analyze their electrochemical transport properties and develop devices for an energy efficient future.

Post-doctoral Project: “High-throughput Discovery of Thermoelectric Materials via Supersonic Aerosol Impaction.” Supervisor: Prof. Chris Hogan (Department of Mechanical Engineering, University of Minnesota, Minneapolis). Funding agency and program: ARPA-E IDEAS

Ph. D. Dissertation: “Atmospheric-Pressure in situ Plasma Reduction and Patterning of Metal-ion Containing Polymers.” Supervisor: Prof. R. Mohan Sankaran (Department of Chemical and Biomolecular Engineering, Case Western Reserve University). Funding agency and program: NSF Scalable Nano-Manufacturing

Research Experience: My academic path has traversed the fields of physics, materials science and chemical engineering. In the process I have developed plasma-assisted direct-write printing, electrochemical ion and gas conversion, and nanoparticle nucleation phenomena in plasmas. The work exposed me to challenges of interfacial phenomena, electrochemical nucleation phenomena, charge fluence and energy transfer through interfaces, and electron-induced reactions. My research showed residence-time and gas-expansion induced control and nucleation of metal nanoparticles in plasmas, with near-100% faradaic efficiency during plasma-electrochemical reactions. I also developed and refined a micro-plasma based direct-write printing technique. Study findings from this research showed a novel phenomenon of plasma-induced migration of nanoparticles through polymers. I was awarded the Coburn and Winters Plasma Science award at the American Vacuum Society meeting (AVS 2016) for this work.

Currently with ARPA-E funding I am engaged in a multi-university effort on scalability and rapid feedback based growth of thermoelectric thin films. A key finding from my work was the effects of the physical parameters such as momentum and energy flux under supersonic conditions on the growth of crystalline thin films. I gained considerable experience in scalability and manufacturing-centric project that relied strongly on inter-university collaborations. I became accustomed to the intricacies required to address stringent reporting and deliverable guidelines for an ARPA-E project. Most importantly, I learned how to negotiate for systematic tangible deliverables within a given time-frame with my funding agency, while keeping my collaborators on board.

Future Direction: Understanding the surface modifiability, reactivity, and electrical and chemical transport through the interface, and subsequent engineering of the same is the key to developing nanoparticle printing as an industry standard. My prior work indicates that strain delocalization and electrodiffusion are two promising surface engineering routes for printing flexible and stretchable structures. However, the underlying physics and chemical processes that can occur in tandem with these phenomena are unknown. As a natural extension of my research, I anticipate that my work will have two primary aims. First, a plasma-assisted materials conversion and printing, and second, supersonic impaction printing of powders and nanomaterials for the additive manufacturing of 2D and 3D structures. In the long term, I envision a printing technique that incorporates in situ combinatorial (stoichiometric control of multiple components) nanoparticle synthesis concomitantly with deposition of thin films or patterns. In situ feedback mechanisms will control the stoichiometry and properties of the materials. Sequential in-line measurement of physical properties will predict and guide the multi-material synthesis process. This approach will optimize the stoichiometric composition of the material based on a desired physical property. By adopting this methodology, I am excited to delve into research on materials discovery and prediction based on transport properties as well as discovering alternative materials and innovative devices.

Taking cues from my post-doctoral experience, I understand that manufacturing is an integrative process. The translation of scientifically proven research from bench-top to industry can be best implemented when scientific analyses is executed at par with system modelling, design, and integrating industry standards. My research will adopt a proactive approach towards low-cost manufacturing, integration of smart electronics, and in situ process-feedback mechanisms. I am confident that this two-pronged approach of scientific discovery in the context of manufacturing scalability is much needed for translating academic research to industrial practice.

In parallel to the research theme of interfacial phenomena, materials discovery, scalable synthesis and additive manufacturing, I foresee myself collaborating closely with theoreticians. Plasma-reactors are scalable and industrially viable, yet most laboratory research either focuses on existing materials to optimize devices or rely on trial-and-error methods to synthesize new materials, as opposed to first-principles approaches. Theoretical simulations, machine learning and predictive modelling are the key to the discovery of materials for next generation energy-efficient applications. Plasma-properties that induce chemical reactions are challenging to predict due to the inherent variability of the electric field intensity and coupling based on reactor geometries. Further, depending on the requisite chemical reaction, the active reactant species can vary from being the electron to ions or radicals and metastables for the same plasma gas. Therefore, I anticipate working closely with collaborators for prediction and validation of my work.

Teaching Interests:

I am comfortable teaching at undergraduate and graduate level courses. As a Ph. D. candidate I served as a teaching assistant for the courses Process control, Process analysis and design and Measurements laboratory. I was responsible for grading and problem solving during these courses except the laboratory course where I was required to supervise, debug and grade experiments. I also mentored 2 graduate, 12 undergraduates, and 2 high school students. In addition, I have published 8 peer-reviewed publications with 7 of them as my coauthors.

Significant Publications:

1. Ghosh, B. Bishop, I. Morrison, R. Akolkar, D. Scherson, and R. M. Sankaran, “Generation of a direct-current, atmospheric-pressure microplasma at the surface of a liquid water microjet for continuous plasma-liquid processing,” J. Vac. Sci. Technol. A 33, 021312 (2015).
2. Ghosh, T. Liu, M. Bilici, J. Cole, I-M. Huang, D. Staack, D. Mariotti, and R. M. Sankaran, “Atmospheric-pressure dielectric barrier discharge with capillary injection for gas-phase nanoparticle synthesis,” J. Phys. D 48, 314003 (2015).
3. Ghosh, E. Klek, C. A. Zorman, and R. M. Sankaran, “Microplasma-induced in situ formation of patterned, stretchable electrical conductors,” ACS Macro Lett. 6, 194 (2017).
4. Ghosh, R. Hawtof, P. Rumbach, D. B. Go, R. Akolkar, and R. M. Sankaran, “Quantitative study of electrochemical reduction of Ag⁺ to Ag nanoparticles in aqueous solutions by a plasma cathode,” J. Electrochem. Soc. 164(13), D818 (2017).
5. Hawtof, S. Ghosh, Cheyan Xu, R. M. Sankaran, J. Renner, “Catalyst-free, high selectivity electrolytic synthesis of NH₃ from N₂ and H₂O by plasma-produced solvated electrons,” Science Adv. (2018) (Accepted).