I am currently a postdoc in Mechanical Engineering at the University of Minnesota working on aerosol deposition of thermoelectric thin films. The focus of the research is to develop a scalable additive manufacturing technique that can produce large-area thin films via supersonic impaction.
My prior research focus during Ph. D. was in the field of flexible and printable electronics. It spanned from developing the chemistry and engineer the hardware technologies enabling microplasma patterned direct-write on flexible thin films and develop precursors for inkjet printing of metallic nanoparticles. During Ph. D. I have also worked on plasma-electrochemical reactions to form metal nanoparticles in solutions and plasma-gas phase reactions to synthesize aerosols. For more information, go to Research.
I received my PhD in Chemical Engineering at Case Western Reserve University in 2017. My advisor was Professor R. Mohan Sankaran. I also have a M.Tech degree in Materials Science and Engineering from the Indian Institute of Technology, Kharagpur and a M.S. degree in Physics from the Bose Institute in Kolkata. For more information, go to CV.
My research has been recognized by the American Vacuum Society (AVS) and Electrostatics Society of America (ESA), including the 2016 Coburn and Winters Student Award in Plasma Technology. For more information, go to Publications.
I enjoy visualizing and expressing my work in the form of 3D models and process flow schematics. My 3D images are rendered using various visualization softwares including, but not limited to Autodesk 3Ds Max, Adobe Photoshop, ChemDraw and SolidWorks. Some of my renditions have been featured on dustflap of Nature Communications, the Journal of Vaccum Science and Technology-A, and the cover of Journal of Physics D. For more examples, please go to Images.
Case Western Reserve University, School of Engineering, Cleveland OH
Specializiation in atmospheric pressure microplasma.
Thesis Title: Atmospheric Pressure Microplasma Assisted Synthesis of Flexible Electronics and Nanomaterials
Indian Institute of Technology, Kharagpur, India
Research on synthesis of one and two dimensional carbon nanomaterials
Thesis Title: Growth of Carbon Nanostructures by Chemical Vapor Deposition
Bose Institute and St. Xavier's College, Kolkata, India
Research on magnetohydrodynamics of the solar corona
Thesis Title: Analysis of Magneto-Atmospheric Waves in a Linear Plasma
St. Xavier's College, Kolkata, India
PI: Professor Chris Hogan
University of Minnesota, Minneapolis, MN
ARPA-E funded position for research on scalable aupersonic aerosol deposition of thermoelectric thin films.
PI: Professor R. Mohan Sankaran
Department of Chemical and Biomolecular Engineering, Case Western School of Engineering, Cleveland OH
National Science Foundation funded position [Scalable Nano-Manufacturing Grant (SNM)]. Research involves research on large scale nanofabrication of metallic electrodes on flexible polymer substrates using an atmospheric pressure microplasma as a tool.
PI: Professor Mohan Sankaran & Dr. Daphne Pappas
Department of Chemical and Biomolecular Engineering, Case Western School of Engineering, Cleveland OH & EP Technologies LLC, Akron OH
In addition to NSF funding, I was also funded by EP Technologies LLC. for a period of 6 months during 2013. This was a pilot project aimed towards fundamental understanding of the difference in anti-bacterial effects between silver nanoparticles and that of silver ions.
PI: Professor Chako Jacob
Materials Science Center, Indian Institute of Technology, Kharagpur, India
Research involved using an atmospheric pressure thermal chemical vapor deposition system for synthesizing carbon nanostructures on non-metallic catalysts.
PI: Professor Parthasarathi Joarder
Center for Astroparticle Physics and Space Science, Bose Institute, Kolkata, India
Research involved first principles simulation of behavior of high temperature plasma in the solar corona under assumption of quasi-equillibrium magnetohydrodynamic conditions.
Coburn and Winters Award Winner PSTD Division, AVS 63rd Symposia: 2016
Scientist of the Week Interview for "The Science and Engineering Cafe": February 2016
NSF Travel Award for Gordon Research Conference: 2016
One of the "Most Downloaded" of 2015 and "Most Read Article" for Two Consecutive Months in the Journal of Vaccum Science and Technology-A: Generation of a direct-current, atmospheric-pressure microplasma at the surface of a liquid water microjet for continuous plasma-liquid processing: Published in May 2015
Featured Article & Journal Cover of Journal of Physics D: Applied Physics,
Special Issue: Plasma synthesis of nanoparticles and nanocrystals: Published in 2015
Research highlighted in CWRU's magazine Think: 2015
AVS PSTD travel award for AVS 60th, 61st, and 62nd symposia: Awarded 2013, 2014, 2015
Electrostatics Society of America conference, Best Student Presenter: Awarded 2013
AVS Ohio chapter meeting, University of Dayton, Best Student Poster: Awarded 2013
Supersonic aerosol printing
Direct write patterning via atmospheric pressure microplasma and inkjet printing for flexible electronics
Metal and metal-oxide nanocomposite design and synthesis
Electrospinning of nanocomposites for stretchable thin films
Lithography and Reactive ion etching
Chemical and physical vapor deposition
Electrical device characterization using current-voltage and capacitance-voltage measurements
Atomic force microscopy, scanning & tunneling electron microscopy
X-ray diffraction, EDS, EBSD, XPS
Dynamic mechanical analysis
X-ray photo-electron,photoluminiscence, IR & UV-Visabsorption spectroscopy and ellipsometry
Languages: C, C++, C#, Fortran 90, Visual Basic
Software: Origin, LabView, Matlab, Fluent, Custom GUI development with LabView
Web Design: HTML, CSS, VB Script
Graphics Editors: Autodesk 3Ds Max, Autocad, Solidworks, Adobe Creative Suite, ChemDraw
Custom hardware development with open-source platforms like Arduino and Raspberry Pi
Adept with machining tools such as lathe, milling and laser microfabriation
Ball milling is a well-established inductrial technique that is implemented for large scale powder synthesis from bulk ingots. We implement this cheap and scalable method to synthesize sub-1000 nm particles dispersed in a solution. When this colloidal dispersion is nebulized, we can create large volumes of dense, dry aerosols.
Considerable amount of efforts were put towards design of a converging-diverging de Laval nozzle. Downstream of the nozzle is pumped to high vacuum, enabling upstream-to-downstream pressure ratio as high of 100. This pressure differential across the nozzle accelerates the flowing gas close to mach 6. Subsequently, the aerosol flowing through the nozzle is impacted on the substrate. High kinetic energy of the aerosol during impactiong leads to melting and solidification, thus creating a sintered thin film.
Plasmas are an essential component used for traditional top-down fabrication of integrated circuit (IC) manufacturing for etching and deposition of thin films.
Microplasmas are a different class of plasmas that can form at atmospheric-pressure and are a localized source of electrons, ions, and radicals. They are formed under non-equillibrium conditions and can be used to selectively modify thin films.
My work reflects the use of an atmospheric-pressure DC microplasma as a tool to direct-write patterns of metalic features in situ at the surface of a polymer thin film. We have been able to successfully demostrate a high degree of conductivity of these structures. Further, we discovered and reported for the first time electrodiffusion as a fundamental mechanism for the formation of these meatallic features at the surface of the polymers.
My work involves analyzing the degree of flexibility and stretchability of these films and engineering methodologies to improve them. Additionally, efforts are also being put towards reducing the feature sizes.
Non-equillibrium plasmas have previously been formed at the surface of ionic liquids. As an alternative approach to fabricate metallic structures on flexible thin films with high throughput, we developed a continuous nanoparticle synthesis apparatus using an atmospheric-pressure microplasma as a tool.
Unlike a conventional batch system, the electrolyte is flown between the microplasma cathode and a platinum anode, both the electronics of which are isolated from the rest of the system. We have been successful in using this system to manufacture high density silver nanoparticles in water at the rate of 10 - 20 mL/min. I am working on developing a new chemistry to synthesize other noble, alloy or semi-conducting nanoparticles using this setup.
In a more traditional electrochemical synthesis approach, we have also implemented an atmospheric-pressure DC microplasma as a cathode for material synthesis. We demonstrated fundamental understanding of solvated electron and dissolved hydrogen atom mediated material reduction. These materials ranged from metal ions such as silver, gold, zinc and copper to gasseous molecules such as nitrogen and its oxides.
I am interested in the following areas of research:
Printable & stretchable multi-functional materials
Large-scale synthesis of nanomaterials
Fabrication of organic electronics
Combinatorial synthesis of aerosols
LINK Quantitative Study of Electrochemical Reduction of Ag+ to Ag Nanoparticles in Aqueous Solutions by a Plasma Cathode
Summary: Solvated electrons are one of the strongest known reducing agent known. This work presents the fundamental understanding of how silver ions reduce electrochemically in the presence of solvated electrons that are created by a plasma at the surface of water.
LINK Microplasma-Induced in Situ Formation of Patterned, Stretchable Electrical Conductors
Summary: Here, we incorporated metal ion containing elastomer composites, cast them as thin films and site-selectively patterned it (direct-write patterning) with an atmospheric-pressure dielectric barrier discharge to form reduced metal agglomerates. We showed that uniaxial strain on these features allows conservation of electrical conductivity of the features upto as high as 30% strain.
LINK Tuning Optical Signatures of Single- and Few-Layer MoS2 by Blown-Bubble Bulge Straining up to Fracture
Summary: This publication is a part of a collaborative effort showing the effect of two-dimensional strain on a monolayer of a two-dimensional material such as molybdenum disulfide. We developed a unique bulging technique that ensures uniform radial straining.
LINK Correlating charge fluence with nanoparticle formation during in situ plasma synthesis of nanocomposite films
Summary: This report presents a fundamental understanding of plasma-induced reduction of metal ions embedded in thin films. We studied the effects of plasma paramters such as plasma power, duty cycle and exposure time.
LINK Atmospheric-pressure plasma reduction of metal cation-containing polymer films to produce electrically conductive nanocomposites by an electrodiffusion mechanism
Summary: This work presents the fundamental understanding of how the atmospheric-presssure microplasma induces diffusion of metal ions embedded in a polymer matrix under the effect of an external electric field.
LINK Atmospheric-pressure dielectric barrier discharge with capillary injection for gas-phase nanoparticle synthesis
Summary: This work presents the use and development of an Argon based novel atmospheric-pressure dielectric barrier discharge (DBD) reactor for gas-phase synthesis of nickel nanoparticles. This publication also shows how adiabatic cooling due to expansion can be used to control the agglomeration of nanoparticle nuclei and subsequently, give us precise control on the size distribution of the nanoparticles.
LINK Generation of a direct-current, atmospheric-pressure microplasma at the surface of a liquid water microjet for continuous plasma-liquid processing
Summary: This work presents the generation of a direct-current, atmospheric-pressure microplasma at the surface of a liquid water microjet that enables solution species to be transported by forced convection. Using this technique, we have been able to synthesize high density silver nanoparticles in water medium at a rate of 10 - 20 mL/min.
LINK Fabrication of Electrically Conductive Metal Patterns at the Surface of Polymer Films by Microplasma-Based Direct Writing
Summary: This work describes our direct-write process to produce electrically conductive metal patterns at the surface of polymers.
I enjoy expressing our work to the scientific community through graphic visualization. Below are some highlighted examples my work and where they were featured.
This was created for Nature Communications about the formation of nanodiamonds at near-ambient conditions.
The research was lead by a Post-Doc of the Sankaran Lab, Dr. Ajay Kumar.
Featured Article & Journal Cover for the Journal of Physics D: Applied Physics.
This cover was for the special issue entitled Plasma synthesis of nanoparticles and nanocrystals, published in 2015.