Physics

REU Available Projects

* Project may operate remotely, due to Covid-19.

Studying Volume Phase Transition of Polymeric Microgels*
Dr. Kiril A. Streletzky, Physics
1 – 2 Students

Microgels are water-filled nanoparticles which reversibly transition from large, soft particles of loosely bound polymer chains to smaller, tightly packed clusters[27, 28]. Their size, shape, density distribution, and swelling/deswelling ratio depend on environmental conditions and synthesis parameters such as solution temperature, pH, salt concentration, cross-linking density, and polymer concentration and molecular weight. Careful synthesis allows control over the resulting particles, which is beneficial for microgel applications as vesicles and bio-sensing agents[21, 23, 29]. In addition to a wide range of applications, microgels are good systems for experimental validation[16] of statistical mechanics models, such as the predicted coil-to-globule transition of loose polymer chains and the Flory-Huggins free energy theory of the volume phase transition of cross-linked amphiphilic polymer. One system of interest is the biocompatible polysaccharide, hydroxylpropylcellulose (HPC). HPC-based microgels transition from a swollen state at room temperature to a de-swollen state above 41°C. The microgel volume decreases by a factor of 3-20 under this transition depending on the synthesis conditions. Two REU students can contribute to a project focused on merging experiment and theory for HPC polymer and microgels: the first student will optimize microgel synthesis (aiming to develop microgels with controllable size and swelling capacity) and a systematic comparison of the phase transition in microgels and in the parent polymer. The second student will learn polarized/ depolarized dynamic and static light scattering to study the structure, dynamics, density distribution, and volume phase transition of synthesized HPC microgels. Students will interact with Kaufman’s group to provide data for phase transition modeling and with Fodor’s lab for imaging. If remote, one student will focus on modeling microgel data with a modified Flory-Rehner mean field theory.

Click here to view Dr. Kiril Streletzky’s CSU Faculty Profile [link]

 


Design, Expression, & Characterization of Protein-Based Materials*
Dr. Nolan B. Holland, Chemical & Biomedical Engineering
1-3 Students

The Holland lab specializes in design, synthesis, and characterization of protein-based materials. These materials are designed from the gene level to achieve desired functionality. This work is ideal for introducing undergraduates to research since there are various levels of complexity to design projects at each student’s level. One project is the development of a general protein-based theranostic platform using protein engineering. Theranostics combines therapeutic delivery with diagnostic imaging for treating a wide range of ailments such as cancer and cardiovascular disease. Our system[30] consists of: 1) a hydrogel nanoparticle that can trap and release drugs, 2) a gadolinium binding domain that is an effective magnetic resonance imaging (MRI) contrast agent, and 3) the incorporation of a short peptide sequences for selectively targeting particular tissues or diseased cells. By using a protein-based system, all of the components can be combined in a single polypeptide that can be synthesized and purified at once. Additionally, the polypeptides are biodegradable and are generally biocompatible. One specific system designed is a theranostic system for the treatment of prostate cancer. Key aspects in the design of such theranostic nanoparticles are the ability of the particles to encapsulate the therapeutic drug and to release it at the appropriate rate to achieve the desired dose at the tumor site. The nanoparticle carrier also needs to be stable to prevent premature drug release. Specific projects include: a) Using molecular biology techniques to design and build genes that code for desired recombinant polypeptides, such as the incorporation of a new targeting motif onto the theranostic particle or modification of the particle core to optimize drug interactions; b) purification of the polypeptides and characterizing their assembly into nanoparticle[31], which will be aided by light scattering in Streletzky’s lab[32] and SEM in Fodor’s lab to determine their shape and size; c) characterization of the kinetics and thermodynamics of the interactions of drug molecules with the nanoparticles and the hydrogel that makes up the core of the particles using techniques such as liquid chromatography, calorimetry, NMR, and optical spectroscopies.

Click here to view Dr. Nolan Holland’s CSU Faculty Profile [link]

 


Enhancing Electron Imaging Capabilities of Soft Matter Systems*
Dr. Petru S. Fodor and Dr. Kiril A. Streletzky, Physics
1 student

Electron microscopies have become the “gold-standard” for high resolution morphological analysis of nano- and micro-scale systems. Unfortunately, using these methodologies to characterize soft matter systems is difficult because: (i) the samples have to be conductive to dissipate the accumulation of charge during imaging; and (ii) the conditions within an electron microscopy chamber are very harsh for soft matter due to high vacuum and thermal damage induced by the imaging beam. Methods to mitigate these issues involve specialized sample preparation methods such as fixation, flash freezing, and staining that distort the actual structure of samples and can reduce the achievable resolution. Since these methods rely on permanent sample fixation, the dynamics of the systems is impossible to study. This is a big limitation for polymeric microgels, where understanding the morphological response to environmental changes, such as temperature, is needed. To this end, the groups of Drs. Fodor and Streletzky have pursued novel sample preparation methods that enable electron microscopy imaging of individual polymeric microgels, under conditions similar with those standard for other soft matter systems[18, 22]. In this context, the students will work on: (i) the design and fabrication of imaging cells that preserve the integrity of the samples while allowing the visualization of nanoparticle dynamics using electron microscopy[33]; and (ii) the development of image processing algorithms targeted at removing the complex noise profiles associated with the beam and signal generation, and the detection electronics[34]. The methods developed will allow the imaging of various soft matter samples in their native environment (e.g. hydrogel nanoparticles from Holland’s lab) while greatly reducing the beam exposure and associated beam-induced damage. The student will become proficient in the use of surface characterization tools for morphological/chemical analysis and acquainted with computational methods of image processing.

Click here to view Dr. Petru Fodor’s CSU Faculty Profile [link]

Click here to view Dr. Kiril Streletzky’s CSU Faculty Profile [link]

 


Phase Transitions in Polymer Gels*
Dr. Miron Kaufman, Physics
1 Student

A polymer gel like polyacrylamide changes the volume by a large factor when a small quantity of solvent is added to the solution or when the temperature is varied slightly. Central to the understanding[35] of this phase transition are the covalent crosslinks between the linear chains. In our model[36], we consider a gel consisting of P polymers of length L and Nz poly-functional monomers. Each poly-functional monomer forms z (covalent) bonds with some or all of the 2P bi-functional monomers at the ends of the linear polymers. We find that the entropy dependence on the number of poly-functional monomers exhibits an abrupt change at Nz = 2P/z. The grand-canonical thermodynamic potential exhibits a kink when represented as a function of the chemical potential of the poly-functional monomers. This corresponds to a phase transition between two gel phases: one poor and the other rich in poly-functional monomers. By further increasing the chemical potential, and thus Nz, the rich gel phase can become thermodynamically unstable. A student will work under my supervision to analyze numerically this thermodynamic model. We will focus on the dependence of various thermodynamic quantities on solvent concentration, the length of polymers, and the functionality of cross-linkers. The student will use the proposed model to analyze microgel data from Streletzky’s lab.

Click here to view Dr. Miron Kaufman’s CSU Faculty Profile [Link]

 


Synthesis and Evaluation of Biomimetic Glycopolymers
Dr. Xue-Long Sun, Chemistry
1 Student

Glycan recognition is deeply involved in both physiological [37–40] and biological [41–44] processes and provides many opportunities to discover the molecular mechanism and potential therapeutic or diagnostic mechanisms for various diseases. Biologically active carbohydrates exist mostly as glycol conjugates (glycoproteins and glycolipids) on cell surface, serving as multivalent carbohydrate ligands. In the past, synthetic glycopolymers were very attractive multivalent carbohydrates for mimicking and studying carbohydrate functions. Most glycopolymers have glycans attached to the polymer backbone through an O-linked spacer or N-reductive amination-linked spacer. Neither of these linkages is native glycan-amino acid linkage in glycoproteins, which might explain the lower performance of glycopolymers so far. N-glycans are mostly found in natural glycoproteins, where the sugar molecule is attached to a nitrogen atom of asparagine (Asn) residue of a protein. N-Glycoside linkage between 2-acetamido-2-deoxy-D-glucopyrano sylamine (GlcNAc) and L-Asn is the most common, but D-galactose (Gal) and D-glucose (Glc) attached to Asn with N-glycosidic linkages have been reported. In this project, we will develop a direct synthesis of arylazide chain-end functionalized N-glycan polymers from free saccharides via glycosylamine intermediates followed by acrylation and polymerization via cyanoxyl-mediated free radical polymerization (CMFRP) in a one-pot synthesis. No protection and deprotection will be necessary in either glycomonomer or glycopolymer synthesis. A typical synthesis of glycopolymers from free saccharide, sialyllactose and mono-, di-, and tri-mannose will be demonstrated. The resultant glyco-polymers will be characterized by NMR and GPC. In addition, the solution dynamics and self-assembly properties of the glycopolymers with different glycan densities/molecular weights and their protein binding activities will be characterized by light scattering[45] in Streletzky’s lab. The chain-end arylazide will be used for site-specific conjugation/ immobili- zation onto proteins, nanomaterials and biosensors, while sialyllactose and mono-, di-, and tri-mannose-containing glycopolymers are expected to serve as ligands/receptors for different proteins and cells.

Click here to view Dr. Xue-Long Sun’s CSU Faculty Profile [Link]

 


Synthesis of Carbon Nanotube-Based Organic Color Centers with Carbohydrate Functionality
Dr. Geyou Ao, Chemical & Biomedical Engineering
1-2 Students

Protein-carbohydrate recognitions are crucial events in many biological processes including cell-cell communication and trafficking, immune response, tissue growth and repair, and cancer development and metastasis[46, 47]. Understanding specific interactions between carbohydrates and carbohydrate-binding proteins has been challenging due to the lack of versatile probes. Organic color centers created on nanomaterial hosts with precise optical and carbohydrate functionalities are uniquely suited to profile protein-carbohydrate recognition, which can lead to clarifying functions of both molecules, their underlying molecular mechanism and discovering therapeutic and diagnostic mechanisms. In this collaborative project with Sun’s lab, organic color centers will be created by covalently functionalizing the sidewall of semiconducting, pure-chirality single-wall carbon nanotubes (SWCNTs) via oriented immobilization of glycopolymers that closely mimic the natural glycan structures and functions. Chirality-defined carbon nanotube hosts have defined structures and properties[48, 49] and color centers created on nanotubes further tune light in the near-infrared regime[50, 51] that has attenuated autofluorescence and deep tissue penetration[52–54], providing the ideal conditions for high contrast fluorescence in complicated biological samples. This project will engage two students in research in an evolving interdisciplinary field of nanomaterial science and glycoscience. Students will learn nanomaterial processing including dispersion, purification, surface functionalization and characterization techniques such as optical spectroscopy and imaging. The skills gained through hands-on research on nanomaterials are industrially relevant in many fields (e.g. nanotechnology, advanced manufacturing, and pharmaceuticals).

Click here to view Dr. Geyou Ao's CSU Faculty Profile [link]

 


Promoting Robust Crystallization of Organic Molecules via Row Surface Reconstructions*
Dr. Jessica Bickel, Physics
1-2 students

Organic electronics are an interesting lower cost and eco-friendlier alternative to fragile crystalline semiconductors that are typically used in electronic applications such as solar cells, but they suffer from lower conductivities. Partially or completely crystallizing these materials significantly improves conductivity while only slightly decreasing mechanical flexibility[55]. In this project, we use row surface reconstructions to induce organic molecule crystallization. Surface reconstructions form as atoms rearrange at the surface to lower the surface energy and the resulting pattern repeats in a periodic fashion across the entire surface. The topography and bonding of the surface atoms defines a non-uniform but periodic energy landscape. This landscape defines how atoms diffuse on the surface and how they are incorporated into the surface. The goal of this project is to use row surface reconstructions to crystalize organic molecules without carefully pairing the molecules and surfaces. The students will develop methodologies to create atomically smooth surfaces in a nitrogen or high vacuum environment and then use thermal evaporation to evaporate a variety of organic molecules from the acene and thiophene families onto these surfaces to examine how the molecules order. In the first summer, the students will focus on the creation of atomically smooth surface reconstructions of Au(110) and Cu(110). In the second and third summers, the students will examine the self-assembly of pentacene, and rubrene to examine the effect of molecule width on ordering. Further, these results will be compared to density functional theory (DFT) calculations that will determine the thermodynamic minimum energy configuration. This work is accessible to undergraduate researchers who can begin calculations without fully understanding the code. Students will examine the same molecules on the same surfaces and by independently varying the surface lattice parameter and chemistry we will examine whether the ordering is driven by topography or chemistry.

Click here to view Dr. Jessica Bickel’s CSU Faculty Profile [link]

 


Crystallization of Anisotropic Particles*
Dr. Jessica Bickel, Physics and Chris Wirth, Chemical & Biomolecular Engineering CWRU
1 student

The ability to economically manufacture useful nano and micro-structure composites is critical, particularly if we can exploit the properties of particles that are anistropic in shape and thus in their properties. Anisotropic materials have significant potential impact because of the unique mechanical, electrical, and thermal properties intrinsic to individual particles. CNTs have been identified as a promising replacement for Silicon-based transistors in next generation nanoelectronics, noble metal nanorods could be used in a variety of sensing applications because of the particles’ exquisite interactions with light, and since conductive polymers are low-cost alternatives to expensive Si-based optoelectronic devices[56–58]. However, current methods typically use magnetic or electric fields to assemble ellipsoidal particles[59, 60], which will not work for all types of anisotropic particles. This work utilizes a blade coating mechanism to examine the crystallization anisotropic particles in order to build up a fundamental knowledge of crystallization in these materials. By utilizing a blade-coater, we can examine the crystallization as a function of both the aspect ratio of the particles and the physical impacts of the deposition process, such as the blade speed, angle, and even the different weights of the particles that will impact how crystalline a material is obtained. Being able to consistently crystallize particles that are not a single mono-dispersed sphere will allow us to build more interesting devices. A student will utilize polystyrene (PS) beads that they will stretch into ellipsoids with different aspect ratios. Future summer researchers will examine the effect of PS ellipsoid surface chemistry and the effect of polydispersity on crystallization. If remote, students can simulate the motion of asymmetric particles near surfaces during deposition/crystallization.

Click here to view Dr. Jessica Bickel’s CSU Faculty Profile [link]

Click here to view Dr. Chris Wirth’s CSU Faculty Profile [link]

 


Mathematical Modeling and Simulation of Active Biosystems and Biomaterials*
Dr. Shawn Ryan, Mathematics & Statistics
1 student

Self-organization is a fascinating process manifested in biological systems that results in interesting physical phenomena such as enhanced movement/mixing, efficient foraging, and striking effective properties in materials. While these striking features can be readily observed, there remains a critical need to identify the main microscopic interactions leading to its emergence. We seek to meet this need by using mathematical modeling, analysis, and simulations[61] studying collective swimming of microscale organisms. This work will focus on the interactions at the microscale that lead to large scale pattern formation as well as to novel effective material properties. This understanding will then be applied to the emerging field of biomaterials to study how materials such as biofluids exhibit enhanced functionality due to the presence of a self-organizing. The principal outcome is a fundamental understanding applicable to a wide-range of similar organisms, many of which are anisotropic. These organisms include sperm, Janus particles[62], colloidal membranes, and granular matter, which are all capable of self-organization. This can also be used to develop microfluidic devices, drug-delivery systems, and biomaterial networks. Any models developed will be guided by experiment on synthetic microswimmers in collaboration with Wirth’s lab.

Click here to view Dr. Shawn Ryan’s CSU Faculty Profile [Link]

 


Stability of Fractal Structures in Cavities*
Dr. Miron Kaufman and Dr. Petru Fodor, Physics
1 Student

This analytical and numerical work is geared towards understanding the flow structures in cavity type systems. This problem is relevant in the design of polymer handling systems, such as single screw extruders, that can be approximated as cavity systems with moving walls. The student in this project will model the formation of fractal flow structures such as Moffatt eddies, that are known to occur for zero Reynolds number. We will examine the stability of the Moffatt eddy structures when the Reynolds number is increased, and under oscillatory conditions (the wall movement is periodic rather that constant in a fixed direction). The student involved in this project will learn the fundamentals of fluid dynamics and mixing. The student will also become familiar with a suite of tools used in modeling complex systems including finite element analysis, development of analytical models and the use of thermodynamic analogies[63, 64].

Click here to view Dr. Miron Kaufman’s CSU Faculty Profile [Link]

Click here to view Dr. Petru Fodor’s CSU Faculty Profile [link]

 


Microfluidic Reactors and Emulsifiers*
Dr. Chandra Kothapalli, Chemical and Biomedical Engineering, and Dr. Petru S. Fodor, Physics
2 Student

Dr. Kothapalli’s lab has been working on the design and implementation of microfluidic platforms to investigate both complex physical (e.g., fluid mixing, chemical reactions) and biological (e.g., cell-cell and cell-matrix interactions) phenomena[65–73]. Compared to conventional platforms, microfluidic devices offer better versatility with varying channel dimensions and architecture, flexibility to gradually introduce compounds and cells of interest, reduced consumption of samples and reagents, provision for in situ imaging and live-monitoring of experiments over long durations, enhanced reaction speed due to increased surface to volume ratios, high-throughput parallel sample processing, and high-content imaging capabilities. Moreover, they allow the implementation of unique methodologies such as droplet microfluidics[74] with applications ranging from chemical and particulate synthesis/analysis, to enabling tools for biotechnology and drug discovery. However, the typical laminar characteristics of the flow field in microfluidic devices pose significant challenges in mixing. In collaboration with Dr. Ao, we are investigating how fluid flow and molecular diffusion evolves spatiotemporally within microfluidic channels, to enable design of better mixers to synthesize metallic, polymeric or biological nano-structures (e.g., particles, spheres)[12, 14, 75–78]. The students will be trained on the development of microfluidic platforms: analytical and numerical modeling, optimization of the reactant flow and mixing, prototype fabrication using advanced manufacturing tools (e.g. soft-lithography), functionality testing of the quality of mixing using optical imaging, and product assessment using chemical and microscopy analysis. One student will investigate the role of microfluidic channel design features (e.g. shape and location of mixing ports, length of channels, tortuosity) on the effectiveness of mixing within the device. A second student will study the characteristics of fluid flow (e.g., velocity, Reynolds number, flow rate, viscosity, scaling factors) and their temporal evolution within the channels. The projects have potential collaborations with other REU labs (e.g. Streletzky’s). If remote, a student will model microfluidics-based emulsifiers.

Click here to view Dr. Chandra Kothapalli’s CSU Faculty Profile [link]

Click here to view Dr. Petru Fodor’s CSU Faculty Profile [link]


Flowing Past Cilium*
Dr. Andrew Resnick, Physics
1 – 2 Students

This laboratory focuses on cellular mechanosensation, specifically the sensing of extracellular fluid flow by ciliated epithelial monolayers. One student will use an existing apparatus to fabricate a novel tissue culture perfusion chamber using “soft lithography”, apply pre-defined steady and oscillatory fluid flow to ciliated cells cultured within the channel, and image the internal flow field and cellular response (intracellular Calcium and/or nitric oxide) with fluorescence microscopy. A second student will stimulate primary cilia directly using optical trapping, applying localized forces directly to individual cilia and imaging the cellular response (intracellular Calcium and/or nitric oxide) with fluorescence microscopy. The mechanical stiffness of cilium[79] will be chemically manipulated, with cilium stimulated either with fluid flow or with optical trapping, and the effect on sensor sensitivity will be assessed by live-cell Calcium imaging. Students will learn basic fluid mechanics (Reynolds & Strouhal numbers), cell physiology (ciliary mechanosensation & directed salt/water transport), biophysical laboratory techniques, microscopy, quantification of a flow velocity field, and fluid-structure interaction. Knowledge of the internal flow-field within cell-free microchannels will be used in collaboration with Drs. Kaufman and Fodor to determine mixing rates and feedback for analytical/computational modeling. This experiment will yield a mechanistic understanding of cellular mechanosensation, inspiring new microfluidic applications. The project can operate remotely with students working on modeling with COMSOL.

Click here to view Dr. Andrew Resnick’s CSU Faculty Profile [link]

 


Waste of Energy via Chemical Reactions in Multiphase Environments*
Dr. Jorge Gatica, Chemical & Biomedical Engineering
1 – 2 Students

An alternative to landfill and incinerator use for dealing with 250 million of tons of waste each year is waste gasification, which breaks down carbon-based materials into synthetic gas. Catalytic processes, studied by this group[80, 81], provide an efficient route to gasify solid residuals. Wet-Thermal Catalytic Oxidation (WTCO) is lower in temperature (T=300-350oC) and energy than incineration (T>1000oC). Common plastics found in municipal waste include long-chain polymers polyethylene, cellulose, and nylon. Cellulose is problematic as it remains solid unlike low melting temperature substrates (e.g. polyethylene), creating a heterogeneous (a particulate or slurry system) reacting environment where interaction must be promoted between catalyst (solid particles), substrate (cellulose particles and/or molten substrates), oxygen (in liquid and gas phases). The fluid dynamics of the stratification of particulates in the WTCO reacting environment in a high pressure stirred reactor presents a formidable problem. In this project, experiments are combined with computational fluid dynamics (CFD) for characterization and optimization. The model substrate is cellulose. The gasification process is studied in a low-to-mid temperature/high pressure reactor. The unit operates in batch, semi-batch, or continuous mode and is well suited for the study of heterogeneous reactions. The system operates as an un-baffled Stirred-Tank Reactor (STR). The mixing parameters are essential in modeling the process and the kinetic analysis. This unit does not allow flow visualization so CFD modeling is essential to optimize gasification. The STR has the highly tangential liquid motion that leads to the formation of a central vortex on the liquid free surface[82, 83]. Slurry systems are characterized by two phases: a discrete phase of bubbles, particles, or droplets, and a continuous phase the particles are immersed in. Modeling and experiments are aimed at characterizing mixing, particle dynamics, and transport phenomena associated with gasifying solid substrates. The goals are to: a) model the waste gasification process of cellulose in a pressure stirred reactor using a finite-element software; b) study fluid dynamics to optimize chemical reaction and transport phenomena; c) characterize catalytic gasification dynamics for cellulose particles; d) scale up to continuous gasification.

Click here to view Dr. Jorge Gatica’s CSU Faculty Profile [Link]

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