- Post Doctoral
MIT Unit Affiliation:
- Mechanical Engineering
Post Doc Sponsor / Advisor:
Date PhD Completed:
Top 3 Areas of Expertise:
I am a nanomanufacturing engineer with a multidisciplinary background and an interdisciplinary research experience. Trained as a mechanical engineer, my PhD research at the University of Michigan in Prof. A. John Hart's group focused on designing and building chemical synthesis reactors, as well as developing characterization techniques based on synchrotron X-rays and modeling tools based on mechanochemical coupling phenomena, for process understanding and control. At MIT, I worked in my first postdoc position in Prof. A. John Hart's group on studying the self-organization of nanoparticles and nanotubes by in situ monitoring using optical and environmental transmission electron microscopy (E-TEM). In my second (current) postdoc position at MIT in Prof. Karl K. Berggren's group, I am working towards sustainable bionanomanufacturing process development by interfacing protein assembly and surface immobilization with sub-10-nm nanolithography.
The breadth and depth of my background in mechanical design and manufacturing combined with my research experience in the fabrication and characterization of nanomaterials and biomolecular assemblies and my leadership experience in mentoring students, communicating work through publications and presentations, and preparing proposals will enable me to create an impactful research program in nanomanufacturing. I personally believe that research in academia should not only focus on pushing the boundaries of scientific discovery, but should also strive to maximize the societal impact. Hence, I will lead my research group towards developing enabling manufacturing and metrology technologies, capable of transforming emerging applications of nanotechnology that are based on ordered and tailored nanostructures.
Expected End Date of Post Doctoral Position:
- "Templated protein self-assembly for advanced materials." PI: Karl K. Berggren. CoPI: Amy Keating. Source of Support: DuPont. Location of Project: MIT.
- "High-speed continuous assembly of nanoparticle monolayers and discrete cluster arrays." PI: A. John Hart. Source of Support: NSF. Location of Project: MIT.
- "Understanding and controlling nanoscale crystal growth using mechanical forces." PI: A. John Hart. Source of Support: DOE. Location of Project: University of Michigan and MIT.
- "Methods for continuous growth of indefinitely long carbon nanotubes." PI: A. John Hart. Source of Support: ONR. Location of Project: University of Michigan.
Hierarchically ordered carbon nanotubes (CNTs) are promising for integration in high-performance structural composites, electrical interconnects, thermal interfaces, and filtration membranes. These and other applications require CNTs that are monodisperse, well aligned, and densely packed. Moreover, because more than 1 billion CNTs per square centimeter grow simultaneously in a typical chemical vapor deposition (CVD) process, understanding the collective chemical and mechanical effects of growth is key to engineering the properties of CNT-based materials. This dissertation presents tailored synthesis processes, characterization techniques, and mathematical models that enable improved control of the morphology of as-grown CNT “forests.”
First, a comprehensive characterization methodology, combining synchrotron X-ray scattering and attenuation with real-time height kinetics, enabled mapping the spatiotemporal evolution of CNT diameter distribution, alignment and density. By this method, the forest mass kinetics were measured and found to follow the S-shaped Gompertz curve of population growth. Dividing a forest into subpopulations revealed size-dependent activation-deactivation competition. Additionally, in situ transmission electron microscopy (TEM) showed that the kinetics of CNT nucleation are S-shaped. Based on these findings, a collective growth model is proposed, wherein randomly oriented CNTs first nucleate then self-organize and lift-off during a crowding stage, followed by a density decay stage until self-termination when the density drops below the self-supporting threshold.
Next, further X-ray data analysis enabled modeling the mechanics of entangled CNTs and proved that mechanical coupling is not only responsible for the self-organization into the aligned morphology, but is also an important limiting mechanism as significant forces ensue from diameter-dependent CNT growth rates. A custom-built CVD system was used for mechanical manipulation of growing CNTs, leading to insights that external forces modulate the reaction kinetics. Last, a mathematical model describing the synergetic chemical coupling among growing CNT micropillars predicted height variations, and enables the design of CNT catalyst patterns for improved uniformity.
The insights in this dissertation contribute to the fundamental understanding of self-organized CNT growth, enabling improved manufacturing and metrology. The models and techniques for studying population behavior of nanofilaments may also be applied to other systems, such as inorganic nanotubes, nanowires, and biofilaments.