Pratt Welcomes Seven 2016-17 NSF Graduate Research Fellows

Advisors: George Truskey and Nenad Bursac
Department: BME
Project: TBD

I am currently in a rotating laboratory program to get to know the various projects I could choose to work on. The project I proposed in my NSF application had to do with engineering E coli to form an autonomous sensing/responding system that could be used for several applications; the one I highlighted in my proposal was biofuel production.

I know that project well, but my actual PhD project will be completely unrelated because I have switched fields. I am now in tissue engineering, so I'll be working on developing either tissue engineered blood vessels or muscle bundles, and there are a lot of possibilities of what I might do with that. I might study the effects of certain drugs, or try to model and study a specific disease, or study the effects of immune cells on regeneration of the muscle. These are all overall aims of the two labs I am rotating in, but I don't actually have a project in either lab. For the few weeks that I'm rotating right now, I'm doing a mini project working on differentiating endothelial cells from induced pluripotent stem cells for use in tissue engineered blood vessels.

Advisor: Aaron Franklin
Department: ECE
Project: Nanomaterial Based Printed Electronics

Historically, efforts have been made to scale down the size and energy consumption of electronics to increase the performance for computing applications. As engineers continue to push the physical limitations of electronics toward atomic scales, the associated costs and technical challenges of doing so are exponentially rising. Meanwhile, there are new and distinct application spaces for electronics that could be accessed using low-cost fabrication techniques and a new class of electronic materials: nanomaterials.

Aerosol jet printing is an additive manufacturing technique that can use nanomaterial inks, such as carbon nanotubes, to print flexible, transparent, and/or biocompatible electronics for distributed sensing and health diagnostic applications. This printing approach opens the way for a myriad of applications in the Internet-of-Things (IoT) space by avoiding the high costs associated with manufacturing high-performance transistors, while drawing from the advantageous electrical, mechanical and optical properties of nanomaterials. Here at Duke, I will be developing nanomaterial inks and corresponding printing parameters for an aerosol jet printer to explore completely new applications for electronics that could never be realized using the traditional semiconductor materials or their associated high-cost fabrication methods.

I joined the Laboratory of Electronics from Nanomaterials at Duke as an REU student during the summer between my junior and senior year of undergraduate school. I initially chose the REU experience because I had yet to gain exposure to the field of nanoelectronics. During this time, I worked with Professor Aaron Franklin and his graduate students to develop a novel way to increase the performance of 2D nanomaterial transistors at the nanoscale. I began to see the complications and the physical limitations associated with improving the performance of nanoscale devices and the costs it would impose on a manufacturing process.

By the time I was applying to graduate school, I already knew I would like to continue to develop physical electronics, but I was looking for a project that I thought would make the biggest impact to technology in the long run. I had already developed a great relationship with Professor Franklin and his group, and I knew about his work in printed electronics from working with him over the summer. Upon further research into printed electronics, I was confident that it was the field to make a big impact on technology. So despite writing my NSF application on developing nanoscale transistors, when I got to Duke I decided to switch directions into the field of printed electronics.

Advisor: Amanda Randles
Department: BME
Project: TBD

My proposal for the NSF Fellowship was related to my past work in the Duke master's program. The project dealt with mathematically modeling the spinal circuitry, which produce activation signals for muscles to generate locomotion. This will ultimately be incorporated in a computational model that is able to optimize a spinal circuitry injury therapy called Neuromuscular Electrical Stimulation. The spinal circuitry model was implemented serially and therefore takes hours, if not days, to complete one simulation. In my proposal, I mentioned computing resources such as Graphics Processing Units to accelerate the simulations and even run more realistic ones. Another component of my proposal dealt with the mathematical approximations using geometric singular perturbation theory, since modeling the spinal circuitry incorporated multiple time scales.

Although I am not continuing my work from my master's program, or even work related to computational neuroscience, I do get to work in a research area that deals with parallel computing and has a biomedical application. I'm very interested in continuing to work with Duke faculty with expertise in parallel computing.

Advisor: Mark Wiesner
Department: CEE
Project: Using Fluorescence Spectroscopy and Protein Characterization To Detect Leaking Wastewater in Surface Water 

In 2013, the American Society of Civil Engineers estimated that approximately 900 billion gallons of untreated sewage are discharged annually in the U.S., much of which stems from leaking wastewater infrastructure. This sewage causes severe ecological problems. Although there have been several past attempts to address this issue, past research has revealed inherent complexities in detecting leaking wastewater.

Given the complexities associated with other strategies, multiple studies have turned to characterizing dissolved organic matter (DOM) from wastewater sources directly. But in recent years, studies have been published that describe innovative approaches for characterizing and quantifying proteins in wastewater, especially fluorescent aromatics. By utilizing these methods, characterization of wastewater has become quicker and less expensive. I propose that these same methodologies can be applied to raw wastewater to detect leaking water infrastructure.

I chose to study at Duke for multiple reasons. In regard to research, the CEE department has a great diversity of research foci, including microbiology and aquatic chemistry. The professors at Duke have also developed many collaborations both domestically and internationally, which could benefit the quality and dissemination of my research. Beyond research, the professors at Duke emphasized the necessity of a healthy work-life balance, which was a quality I desired in my future graduate education. 

I chose this specific project because it combined the concepts from my two sustained research experiences as an undergraduate. Aside from performing a study in characterizing surface waters in my hometown, I also performed research related to microbiology and protein characterization. Hence, this proposed project combined two of my interests in research while also giving me some leeway to choose where I could conduct this study.

Advisor: Joel Collier
Department: BME
Project: Synthetic Peptide Vaccination for Therapeutic Use

I am working with synthetic peptides to modulate the immune system for therapeutic benefit. By utilizing a modular, self-assembling synthetic peptide system, our lab is working to control immune reactions with chemically defined materials. 

I chose Duke University for my graduate studies because of the welcoming and collaborative environment as well as the caliber of research being conducted here. I am currently in the process of defining my thesis project in my first year at Duke.

Advisor: David Mitzi
Department: MEMS
Project: Novel Materials for Photovoltaic and Sustainable Energy Applications

As a first-year PhD, my project is still gaining shape. However, throughout my years at Duke I intend to develop and test innovative, new materials for solar cells and sustainable energy applications. My focus is on thin-film compound semiconductors, specifically chalcogenide-based materials. This focus is inspired by the success of materials such as CdTe and Cu-In-Ga-Se in the global solar cell market. In collaboration with computationally focused research groups, I will predict what materials are worth investigating experimentally. I will then fabricate, test and experiment with the new material until I find sufficient electrical, structural and optical properties to make a full photovoltaic device with the intention of surpassing the performance of the established technologies.

When I began considering graduate school, I focused my search to universities and research groups that investigate sustainable energy devices, specifically solar cells. Duke caught my eye as a school that is quickly developing into a hub for sustainable energy research and development, with close ties to companies committed to the same goal. The quality of professors and Duke’s commitment to graduate student success kept me going back to the university’s website over and over again.

Besides the cutting-edge research, what first drew me to my specific research project was the enthusiasm of the principal investigator, Professor David Mitzi, and the collaborative nature of his research group. Also, the research done in his lab has direct implications on the performance of real, tangible solar cells. The underlying physics are studied to make new and improved devices, and that is exactly what I would like to do during graduate school and beyond. I believe the research in this group, including my own project, has the possibility to truly affect the energy market’s landscape now and in the future.

Advisor: Nenad Bursac
Department: BME
Project: Vascularization and Scale-Up of Engineered Cardiac Tissues

Irreversible loss of cardiomyocytes during myocardial infarction (MI) often leads to functional deterioration, heart failure and, ultimately, death. While promising, MI therapies involving injection of functional stem cell-derived cardiomyocytes (CMs) into the heart are hampered by low survival and retention of injected cells. This problem is greatly reduced when CMs are delivered as an engineered cardiac tissue patch; however, the lack of functional vasculature within tissue patches limits their thickness and ability to deliver large numbers of CMs needed for human therapy. Because of this limitation, current engineered tissues generate forces that are too weak to significantly contribute to heart contractions. Vascularization by endothelial cells (ECs) is critical to scaling up the function of cardiac tissues. I differentiate induced pluripotent stem cells (iPSCs) into CMs and ECs and co-culture them in tissues to generate "blood vessel-like" structures. Implanting these tissues could allow these structures to rapidly integrate with host vasculature to ensure proper nutrient delivery to the implanted cells.

Unlike most programs in the country, the BME department at Duke does not encourage rotations in multiple labs during the first year of the PhD. Students are accepted directly into the lab where they will spend the entirety of their graduate work. While this might deter students who lack well-defined interests, I knew that I was interested in tissue engineering that could have a big impact on society. Dr. Nenad Bursac specializes in cardiac and skeletal muscle tissue engineering. Since heart disease is the number one killer on the planet, I thought cardiac tissue engineering was exciting and had potential to save numerous lives. Dr. Bursac is a passionate researcher with many ideas to improve the function of cardiac tissues to move the field closer to clinical translation. One of the most interesting aspects of cardiac tissue engineering is the ability to see your tissues contract by eye, just like a beating heart! In addition, I am excited about the ability to use human iPSCs to make virtually any type of cell. I have differentiated CMs, ECs, and even macrophages, which may be an important supporting cell type for vascularization. Working with human cells is rewarding because I feel closer to clinical translation than others who commonly use rodent cells, which are much easier to obtain but less relevant. Especially important to me are the personalities of the members of Dr. Bursac's lab. I will spend six years in this lab, so I want to be sure I like and trust them. The members of my lab are extremely nice and, importantly, are always willing to teach me something that I do not know. I certainly made the right decision to work at Duke in Dr. Nenad Bursac's lab.

Advisor: Michael Zavlanos
Department: MEMS
Project: Stochastic Source Identification for Mobile Robots

This is not my original research project I proposed in the NSF Fellowship application, but I am interested in using mobile robots to solve the "source identification problem." Source Identification refers to determining the location, shape and intensity of an unknown source emitting within a domain. This could be a sound source, smoke source or any kind of source emitting something whose resulting intensity or concentration field can be measured. By having a robot take measurements of concentration within a room, the objective is to determine the location, size and intensity of the source or multiple sources. 

A future experiment we wish to conduct is to use drones to track and follow other drones by means of sound only. This is appealing because tracking by means of cameras is difficult without light (i.e. at night) and in complex environments where line of sight might not be available. To achieve this goal, I am trying to solve the problem in a stochastic setting. This will lend itself well to experiments because in reality, your model of the physical phenomenon is not exact and is subject to underlying uncertainties. We need to construct algorithms robust to these uncertainties.

I chose Duke mainly because of my adviser, Michael Zavlanos. I was interested in robotics and control, and I found his work on distributed systems and multi-agent control very interesting and appealing. After speaking with him a few times, we got along well and I figured we would work well together. My project has many future directions that need to be explored and I was very interested in performing real experiments with robots to accomplish tasks that were previously unimaginable. This project presented such an opportunity!

Advisor: Amilcare Porporato
Department: CEE
Project: Advancing Model Predictions of Crassulacean Acid Metabolism (CAM) Photosynthesis 

Crassulacean acid metabolism (CAM) photosynthesis is a process used by about seven percent of plant species, mostly in arid and semiarid regions of the world, where they may occupy 48 percent of all plant biomass. CAM plants, which include pineapple, opuntia, agave, among many other cacti and bromeliads, show a high degree of promise for cultivation in arid and marginal lands. Due to a water use efficiency which is three-to-six fold higher than plants with other photosynthesis types, CAM plants achieve a comparable annual productivity with only 20 percent of the water demand. They also show a strong tolerance to high temperatures, withstanding temperatures up to 70 C, compared with 50-55 C for typical plants.

CAM plants, and, in particular, Agave tequilana, show great potential for use in biofuel production in areas of the world where cultivation of other crops is not possible. They are able to maintain a high annual productivity and sugar content even under poor conditions and with low inputs. More widespread use of these crops in biofuels may help alleviate tensions between food and fuel production since they could be cultivated on marginal land which is not viable for other food crops.

While generally accepted and widely used models for C3 and C4 photosynthesis exist, models of CAM plants have not allowed coupling with atmospheric conditions until very recently. New advances have succeeded in capturing their inherent circadian rhythm, which functions under continuous light conditions but is also strongly affected by environmental variables such as light, temperature and moisture. However, numerous questions about CAM photosynthesis and its coupling to the water cycle, soil and atmosphere persist. The motivation for my research is to advance CAM model predictions so that we may understand the wider implications of CAM photosynthesis for the environment and society. This will contribute to understanding of the trade-offs between C3, C4 and CAM photosynthesis, as well as those between food security and biofuel production in arid regions, which could benefit from CAM cash crop.

I first came to Duke for a Research Experience for Undergraduates (REU) program during the summer after my junior year of college. I enjoyed the experience, and came back to work for the same lab as a graduate student. I am particularly interested in sustainable agriculture and believe that CAM photosynthesis is an interesting, under-explored, and intellectually challenging research topic. So far, I've been involved in both experimental and theoretical work to advance this project.

Advisors: Joseph Izatt and Warren Warren
Department: BME
Project: TBD

I am jointly advised by Professors Joseph Izatt and Warren Warren, who have different areas of expertise within the broad field of optical imaging, and we are still narrowing down projects for me to pursue. The Izatt lab does research in optical coherence tomography (OCT), which is like ultrasound imaging except with light that can acquire structural images very rapidly. The Warren lab does research on pump-probe imaging, an emerging technique that has access to chemical information without the need for molecular probes. The idea is, can we combine these imaging modalities to produce something even more exciting? OCT has seen a lot of success in translation into medicine, particularly in ophthalmic imaging, while pump-probe imaging is still largely experimental. Can we port over some of the success from OCT to pump-probe?

I applied to graduate school with interests in optical imaging and image analysis, and was excited by the prospect of working with two well-known professors in two different areas of optics. They had wanted to collaborate in the past, so I thought this would be an exciting opportunity to bring the two fields together.