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2021 Summer Research Poster Session

2021 VINSE Interactive Summer Research Virtual Poster Session will be held on Thursday, August 5, 2021 from 10am-12pm. Posters will be evaluated by both a panel of judges and virtual poster session attendees for an opportunity to win travel grants to support the cost of presenting posters at a National Conference. Awards will be announced in Gather live at 1pm.  


Thiago S. Arnaud1, Mingze He2, Josh Nordlander3, Jon-Paul Maria3, Joshua D. Caldwell2
1 Department of Mechanical Engineering, Florida International University, Miami, FL
2 Department of Mechanical Engineering, Vanderbilt University, Nashville, TN
3 Pennsylvania State University, State College, PA

Thermal radiation describes the emission of electromagnetic waves from an object whose temperature is above absolute zero.  Thermal emission for objects near or just above room temperature are typically peaked at wavelengths within the long-wave-infrared (7 μm-14 μm wavelengths). This allows for the possibility of thermal imaging, the visualization of the thermally emitted infrared light from objects. A blackbody is one that thermally emits a broadband of infrared and potentially visible and ultraviolet light that is mathematically defined by Planck’s Blackbody Radiation Law. A graybody is an object that still follows this same mathematical function but is scaled to a lower emitted power by the object’s emissivity characteristic. Thus, by assuming objects within a thermal image are graybodies, this concept can be used to approximate the temperature of the objects by correlating it to the emitted power using a thermal imaging camera (TIC). However, this approximation falls short for objects where the emission is not well-described by this law and for those that are highly reflective in the spectral range of interest.  Thus, we have employed inversely designed, aperiodic, Distributed Bragg Reflectors (DBRs) as optical filters that serve to only transmit a defined spectral range, allowing us to directly image thermal emission, more accurately determine materials and their actual temperature. These selective spectral filters are comparable to the Red-Green-Blue (RGB) filters used in cameras for visible light. Those RGB filters have allowed for more complicated imaging and so the same is now being applied for thermal imaging.

Kellen P. Arnold1, Sami I. Halimi2, Joshua A. Allen1, Shuren Hu2, and Sharon M. Weiss1,2,
1 Interdisciplinary Materials Science, Vanderbilt University, Nashville, TN
2 Electrical Engineering, Vanderbilt University, Nashville, TN

Photonic crystals (PhCs) are among the nanophotonic structures with the most degrees of freedom in tuning their dispersion and light-matter interaction. PhCs have been tailored for a variety of technologies including optical sensing and trapping, on-chip communications, and quantum information processing. One of the keys to controlling the optical properties of PhCs is the design of the unit cell, which plays a critical role in light confinement and the modal profile. Over the past few years, we have shown that engineering the unit cell to include subwavelength features unlocks further design freedoms to enable, for example, extreme energy density at the “knot” of a bowtie shape incorporated into a circular PhC unit cell.1 Here we demonstrate that another shape that has synergy with the plasmonic metamaterial community – a split ring2 – can be the basis for a PhC unit cell that offers tunable peak field intensity in a spatially localized air region where single photon emitters or biological molecules are located.

Three-dimensional finite difference time domain (FDTD) simulations were carried out to investigate a silicon split ring photonic crystal (SRPhC). A schematic of the SRPhC is shown in Fig. 1a with the unit cell parameters that can be tuned, including various dimensions and the rotation angle, indicated in the inset. By employing Bloch periodic boundary conditions and using dipole excitation with transverse electric polarization, the mode profile (e.g., Fig. 1b) and band structure are calculated as a function of the rotation angle of the SRPhC unit cell. Notably, the asymmetry of the SR enables the rotation angle of the unit cell to control the peak field intensity inside the split as well as the air band edge frequency, as shown in Fig. 1c. This unique rotational dependence of the optical properties is not present in traditional PhCs with circular-shaped unit cells. As the rotation angle of the split ring is varied from 0 to 90˚, the peak field intensity inside the split decreases by nearly one order of magnitude and the air band edge frequency decreases by 0.75 THz. Fabrication of SRPhCs at the Center for Nanophase Materials Sciences is in progress with transmission measurements to be carried out at Vanderbilt University to verify the novel properties revealed by the FDTD simulations.

Figure 1. (a) Schematic of SRPhC with adjustable parameters indicated in the inset. (b) Field distribution in the zero-degree rotation SRPhC unit cell at air band edge (split width = 10 nm). (c) Change in peak field intensity and air band edge frequency as a function of rotation angle.

  1. Hu, S., Khater, M., Salas-Montiel, R., Kratschmer, E., Engelmann, S., Green, W. M. J., & Weiss, S. M. (2018). Experimental realization of deep-subwavelength confinement in dielectric optical resonators. Science Advances, 4(8), eaat2355.
  2. Smith, D.R., Padilla, W.J., Vier, D. C., Nemat-Nasser, S. C., & Schultz, S. (2000). Composite medium with simultaneously negative permeability and permittivity. Physical Review Letters, 84(18), 4184–4187.

This work was supported in part by the National Science Foundation (ECCS1809937).

Mina Aziz, Payton Stone, Hayden Pagendarm, John Wilson
Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN

Cancer immunotherapies, such as immune checkpoint blockade (ICB), have improved the efficacy of cancer treatments compared to conventional antitumor therapies in a subset of patients; however, there is a demonstrated limited efficacy in many patients. Utilizing innate immune agonists, such as cyclic dinucleotide (CDN) agonists for activation of stimulator of interferon genes (STING), has been demonstrated to increase antitumoral immunological response by activating and recruiting antitumor killer T-cells to the tumor site. Unfortunately, due to barriers in drug delivery – limited access to cytosolically located STING, rapid clearance, and limited cell-specific targeting – free CDN efficacy is limited. Recently, pH-responsive, polymeric nanoparticle mediated drug delivery approaches have been developed to circumvent these concerns. However, production techniques for these nanoparticles are relatively low throughput and variable, inhibiting clinical translation. Here, we utilize a high throughput flash nanoprecipitation (FNP) polymersome formulation platform to reproducibly formulate large quantities of polymeric nanoparticles. Utilizing a confined impingement jet (CIJ) mixer to facilitate nanoparticle self-assembly, we substantiate that the FNP platform results in an improvement in batch-to-batch variability, scalability, and particle size distribution, thus overcoming the previous inadequacies in polymersome formation and accelerating their clinical use.

Amber Cui1, Alexander Sorets2, Ethan Lippmann1,2
1 Department of Chemical And Biomolecular Engineering, Vanderbilt University, Nashville, TN
2 Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 

Aging is the strongest risk factor for neurodegeneration, with a majority ofthe elderly population experiencing cognitive decline. While many factors drive disease progression, impaired microglial dysfunction has recently emerged as a common hallmark of many age-associated neurodegenerative disorders. As the resident immune cell of the central nervous system (CNS), microglia serve important functions including monitoring the CNS for pathogens and apoptotic signals. However, in disease states, chronic overactivation of microglia contributes to neurotoxicity and promotes disease progression, particularly in the context of Alzheimer’s Disease. The potential to explore microglia immunomodulation in culture is an invaluable tool to help mitigate age-associated neurodegenerative disease. We established a protocol to isolate microglia from the rodent CNS and maintain them in culture. This efficient method involves dissociating mouse brains into single cells with high viability, followed by magnetic sorting using beads coated with the antibody cd11b, a microglia-specific marker. Microglial identity was confirmed by flow cytometry for cd11b and immunostaining for iba1. Microglia were maintained in culture for up to a week and retained high viability and cellular identity. Furthermore, the magnetically sorted microglia were highly abundant with over 6,000 cells and enriched in microglia-specific markers compared to the remainder of the dissociated cell population. To demonstrate the versatility of the protocol, microglia were similarly isolated from rat brains and successfully cultured. For future work, observing phenotypic changes in microglia after siRNA-mediated gene silencing and applying therapeutics to diseased murine microglia will be explored in hopes of improving our understanding of treatments for neurodegenerative disease.

Brooke C. DeMarco1,4, Ruben Torres2,3,4, Ian D. Tomlinson2, Oleg Kovtun2, James R. McBride2,4,5, Evan S. Krystofiak6, Sandra J. Rosenthal2,3,4,7,8,9
1 Department of Biomedical Engineering, Vanderbilt University, Nashville, TN
2 Department of Chemistry, Vanderbilt University, Nashville, TN
3 Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN
4 Vanderbilt Institute of Nanoscale Science and Engineering, Vanderbilt University, Nashville, TN
5 Department of Interdisciplinary Materials Science, Vanderbilt University, Nashville, TN
6 Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN
7 Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN
8 Department of Pharmacology, Vanderbilt University, Nashville, TN
9 Department of Physics and Astronomy, Vanderbilt University, Nashville, TN

The dopamine transporter (DAT) is a presynaptic transmembrane protein that drives dopamine reuptake. Abnormalities in DAT function and localization have been linked to various neuropsychiatric disorders including attention-deficit/hyperactivity disorder (ADHD), bipolar disorder (BD), and schizophrenia. Prior studies carried out in transiently transfected monolayer cell culture suggest that abnormal DAT diffusion contributes to the aforementioned disease states. Still unknown is the degree to which DAT surface diffusion is physiologically relevant in natively expressing cellular systems. Rat pheochromocytoma (PC-12) cells naturally express DAT, and upon nerve growth factor (NGF) differentiation, upregulate DAT at neurite terminals.  Here, we implement a fluorescent monoamine transporter reporter, 4-(4-(dimethylamino)phenyl)-1-methylpyridinium (IDT307), to assay the presence of endogenous DAT. A significant loss in cell fluorescence using DAT and other transporter inhibitors indicates DAT presence. Using fluorescence microscopy, we apply our DAT-specific 2-β-carbomethoxy-3-β-(4 fluorophenyl)tropane (β-CFT) antagonist conjugated quantum dot (QD) probe system to track DAT in PC-12. Dynamic imaging revealed a mobile population of QD’s with an average diffusion coefficient (mean ± SEM: 0.018 ± 0.002 μm2/s) comparable to previously reported values. Our results suggest the presence of endogenously expressing DAT in PC-12 and demonstrate the utility of our antagonist-conjugated QD probe to specifically label unperturbed DAT in increasingly complex cellular environments. Insight gained from this study can be advantageous in drawing conclusions on the normal and dysfunctional diffusional behavior of DAT in native cellular architectures.

Santiago Lopez1, Jenna Mosier2, Addison White2, Cynthia Reinhart-King2
1 Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA
2 Department of Biomedical Engineering, Vanderbilt University, Nashville, TN

Metabolic heterogeneity plays a crucial role in cancer tumor expansion. Characteristics of the tumor microenvironment, like oxygen and glucose availability, contribute to the genetic diversity of the cancer cells as they have stem-like qualities. The genetic diversity in cancer cells makes the cells more likely to preferentially utilize different metabolic pathways from normal cell populations. Abnormal metabolic processes can then drive cancer cells to metastasize throughout the body. While it’s known that metabolic heterogeneity is important in metastasis, it is unknown whether this heterogeneity is passed down during cell division. ImageJ analysis and the ratiometric PercevalHR probe transduced in MDA-MB-231 breast cancer cells were used to quantify ATP:ADP ratios before and after cell division. Here, we show that there is no significant difference between the ATP:ADP ratios between the parent and daughter cells before and after cell division. Thus, bioenergetic heterogeneity is a heritable trait during cell division, providing a foundation to determine the feasibility of sorting cells based on ATP:ADP ratios. Overall, this work gives a better understanding of the bioenergetics at play in tumor migration and may point to targeted metabolic therapies for metastasis. 

Ákánké D. Mason-Hogans1, Co D. Quach2,3, Justin B. Gilmer3,4, Clare McCabe2,3,5
1 Department of Chemical, Biological, and Bioengineering, North Carolina A&T State University, Greensboro, NC
2 Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN
3 Multiscale Modeling and Simulation Center, Oak Ridge National Laboratory, Oak Ridge, TN
4 Interdisciplinary Materials Science, Vanderbilt University, Nashville, TN
5 Department of Chemistry, Vanderbilt University, Nashville, TN

Micro- and nano-scale mechanical systems often have lubrication issues that prevent them from operating at full potential. Coating device surfaces with monolayer films to lubricate them shows promise in reducing friction and wear. This project aims to more efficiently identify monolayer films that exhibit low coefficients of friction (COF) and adhesive forces (F0) and can be used to improve the lubrication of both micro- and nano-scale systems. Current evaluation methods that examine systems either by experimentation or computer simulation are impractical because of the vast design space. Our goal is to develop a large-scale screening method that performs a rapid estimation of the tribological properties of candidate monolayer coatings that differ in their terminal group chemistry and allows the examination of more potential coatings. To achieve this, using simulation data performed on a small subset of systems, we are constructing machine learning (ML) models using the random forest regressor algorithm. ML is a method of data analysis where a machine identifies patterns from a training set of data, and then uses the model developed to make predictions for unknown systems. Here, we are considering molecules retrieved from an online library of small molecules that results in ~300,000 dissimilar monolayer systems to be evaluated. After iterating through all these systems and obtaining predicted COF and F0 values, we will identify the top ~20 systems that provide the most favorable tribological properties. These candidate systems will then be simulated using molecular dynamics and traditional experimentation to confirm their properties and utility as lubricants for micro- and nano-devices.

Ray A. Matsumoto, Matt W. Thompson, Yu Zhang, Wei Zhao, Xiaobo Lin, Peter T. Cummings
VINSE: Vanderbilt Institute of Nanoscale Science and Engineering. Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN

Supercapacitors are electrochemical energy-storage devices that store energy through the physical adsorption of ions at electrode surfaces.  As a result, supercapacitors can store and deliver energy at a faster rate but store less energy in comparison to batteries.  Supercapacitors are thus relegated to applications such as regenerative braking and memory backups on personal computers, where fast charge/discharge rates are a priority.  In order to meet the growing energy demands of the 21st century, supercapacitors must be improved to achieve use in widespread applications.

In order to develop next-generation supercapacitors, the mechanisms of ion transport must be understood at a molecular level.  Several approaches in which to study ion transport with molecular simulation are outlined.  These approaches include a computational screening study of 400+ ionic liquid and organic solvent mixtures, the analysis of local correlations through the Van Hove function, and the investigation of confinement effects.

Nicole K. Moehring1-3, Pavan Chaturvedi2, Piran R. Kidambi2,3
Interdisciplinary Graduate program in Materials Science, Vanderbilt University, Nashville, TN
Chemical and Biomolecular Engineering Department, Vanderbilt University, Nashville TN
Vanderbilt Institute of Nanoscale Science and Engineering, Vanderbilt University, Nashville, TN

Atomically thin membranes present transformative opportunities for size selective ionic transport. Although the reported orders of magnitude differences in proton permeation through graphene highlights the role of imperfections and defects, a fundamental understanding of the defect size and its influence on transport remains elusive. Here we systematically vary graphene synthesis parameters and probe its influence on crystalline quality and ionic transport in liquid and gas phase.  Our work presents a practical and scalable route to enable atomically thin membranes for ionic separations of relevance to fuel cells, redox flow batteries, hydrogen pumps and isotope separations.

Avery Nguyen1, Bradly Baer2, Greg Walker3
1 Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA
2 Interdisciplinary Materials Science Program, Vanderbilt University, Nashville, TN
3 Department of Mechanical Engineering, Vanderbilt University, Nashville, TN

The group III nitrides are a well-studied class of semiconductors with a desirable set of physical properties and a wide range of applications in modern electronic and optical devices. Recently, the behavior of superlattice structures composed of these materials has become the subject of additional interest, as superlattices are highly tunable and often exhibit properties not observed in the pure materials. Insights into the unique behavior of these heterostructures and how they can be engineered will help inform the design of new optical materials and devices.

In order to understand the transport of vibrational energy in these materials, we use information from Raman spectroscopy. Utilizing density functional theory (DFT), we first calculate the Raman spectra of AlN and GaN, demonstrating the ability of simulations to accurately calculate phonon frequencies and locate Raman peaks. We then compute the Raman spectrum for the superlattice consisting of alternating unit cells of AlN and GaN. For this structure, we predict several additional Raman-active frequencies that are unique to the superlattice, indicating possible interface modes. These calculations represent new insight into the physical behavior of superlattice structures at the atomic scale.

Shintaro Toguchi1, En Xia Zhang1, Daniel M. Fleetwood1, Ronald D. Schrimpf1, Stephane Moreau2, Severine Cheramy2, Perrine Batude2, Laurent Brunet2, Francois Andrieu2, and Michael L. Alles1
1 Electrical Engineering and Computer Science, Radiation and Reliability group (RER), Vanderbilt University, Nashville, TN
2 Laboratoire d'électronique des technologies de l'information (CEA-Leti), France

Total-ionizing-dose (TID) effects are compared in conventional high-temperature (HT) processed planar Fully depleted silicon-on-insulator (FD-SOI) MOSFETs and 3D-sequentially integrated (3DSI) FD-SOI MOSFETs - HT processed bottom device and low-temperature (LT) processed top device. The bottom-layer devices shows significant increase of the channel resistance after irradiation due primarily to increased interface- and border-trap formation at the buried oxide (BOX)/SiO2 interface and/or lateral charge non-uniformities in the BOX. The radiation-induced degradation in top-layer devices is attributed to the increased resistance of below-spacer regions due to low dopant diffusion by the LT process. Furthermore, 3DSI transistors show strong layer-to-layer coupling of TID responses under specific bias condition due to radiation-induced trapped charges in the intermediate dielectric region between upper and lower device layers.

Addison White, Jenna Mosier, Cynthia Reinhart-King
Department of Biomedical Engineering, Vanderbilt University, Nashville, TN

Of the yearly 9.6 million cancer-related deaths around the world, an estimated 90% are due to metastasis, or the stage at which cancer spreads from its primary location to form secondary colonies. From the primary tumor, metastatic breast cancer cells invade the surrounding extracellular matrix to reach the bloodstream. Physical properties such as stiffness, porosity, and density of the primary tumor microenvironment have previously been shown to influence both the migratory ability and internal metabolic pathways of cells confined within it. The long-term effect of cell confinement on cancer cell metabolism is largely unknown. To investigate the existence of this “metabolic memory”, collagen microtracks were formed using polydimethylsiloxane stamps to mold collagen into desired track geometries.  MDA-MB-231 cells expressing the PercevalHR probe were seeded into these microtracks and the energy utilization of cells was quantified as ATP:ADP ratios as the cells migrated from confined (7 µm wide) to unconfined (15 µm wide) regions of the microtracks. ATP:ADP ratios were found to increase as cells traveled through confined regions, and ATP machinery relocalized towards the leading edge of the cell. High ATP:ADP ratios were temporarily maintained once the cells left confinement, suggesting metabolic memory may play a role in cell migration. Furthermore, the duration of this memory is directly dependent on the distance traveled in confinement, indicating that cells are conditioned by confinement. By further understanding cancer cell metabolism and its relationship to migration, specific therapeutic targets can be identified in preventing metastatic spread.

Alessia Williams1,2, Joshua Passantino1, G. Kane Jennings1
1. Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN
2. Department of Chemical Engineering, Prairie View A&M University, Prairie View, TX

Photosynthesis, the conversion of light energy to chemical energy, is the foundation for the sustainability of all life on Earth. One of the proteins responsible for this energy conversion is Photosystem I (PSI). Its robust reduction/oxidation capability makes it a primary candidate for enhancing solar cells with the more efficient nanotechnology found in nature. The Photosystem I protein has unique structures, namely the P700 site, that can accept electrons from a wide range of donors and the FB site that has one of the most negative reducing potentials found in nature (-0.6V vs SHE). Gel and liquid mediators have allowed electrons access to the P700 site buried within the protein through diffusion. However, we have grown a conducting polymer from the P700 site to allow for direct electron transfer. This polymer growth was accomplished by utilizing the redox capabilities of the Photosystem I protein to oxidize the pyrrole monomer to form polypyrrole. The sunlight powers the reaction, and the P700 site oxidizes the monomer, allowing it to grow and form a protein-polymer conjugate. A solution of dialyzed PSI protein, pyrrole monomer and a dopant/surfactant is exposed to sunlight to produce a protein-polymer conjugate. The characteristics of which are analyzed using gel electrophoresis, IR spectroscopy, qualitative measurements, as well as UV-Vis spectroscopy. This research aims to test multiple dopants and analyze their effect on the characteristics of the Photosystem I protein-polypyrrole conjugate.

Dylan Geiger1, Ivan Ntwari2, Michal Perez3, Tara Stanley4 
¹Electrical Engineering, ²Mechanical Engineering, ³Chemical Engineering, Neuroscience
Vanderbilt University, Nashville, TN.

Each summer Vanderbilt Institute of Nanoscale Science and Engineering selects four undergraduate students to join the VINSE Tech Crew. The Tech Crew is a unique program which trains these undergraduates to assist users, fabricate materials for research groups, and support the VINSE vision. An immersive research project was assigned to every member of the Tech Crew. This poster overviews the projects of each team member which include electron beam lithography misalignment, photolithography and microfluidic device fabrication, and process development and characterization by plasma enhanced deposition and reactive ion etching.