Physics

REU Available 2017 Projects

Structural control and macroscopic assembly of boron nitride nanotubes
Dr. Geyou Ao, Chemical & Biomedical Engineering
1 Student

Boron nitride nanotubes (BNNTs) are an emerging nanomaterial with promising properties for applications in new flame retardant materials, and elevated temperature and hazardous environmental corrosion protection for aerospace applications. BNNTs have a 1D tubular nanostructure, and are inherently noncytotoxic, mechanically robust, and have extraordinary chemical and thermal stability. However, no scalable synthesis solution is currently available for making BNNTs with defined structure and properties. This structure polydispersity of BNNTs presents special challenges for its processing and applications. In this project, the student will explore dispersion and post-synthesis separation of BNNTs using DNA. The initial step involves the fundamental understanding of dispersion quality and yield of BNNTs in various solvents using DNA as stabilizing agents. The next step is to investigate the effect of different polyelectrolytes on BNNT length sorting through selective precipitation. Ultimately, more application relevant development such as flame retardant coatings will be explored using BNNTs with controlled structures. The student will learn the dispersion and characterization of nanomaterials, their interactions with biomolecules, and macroscopic assembly of nanomaterials for application development.

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


Drug Delivery Nanoparticles
Dr. Nolan B. Holland, Chemical & Biomedical Engineering
1 student

To increase the effectiveness of drugs while minimizing their side effects, nanoparticles can be used to carry drugs to diseased tissues and release them in this localized area.  Protein-based materials have been shown to produce nanoparticles which are capable of carrying drugs.  Controlling the size of these nanoparticles is critical for their use as drug delivery vehicles.  Different methods for controlling the size of the nanoparticles will be investigated and the size and shape will be characterized.

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


Polypeptide Bio-inks
Dr. Nolan B. Holland, Chemical & Biomedical Engineering
1 student

With the emergence of 3-D bioprinting technology for tissue engineering, there is a need for biomaterials that can be printed as fluids, yet will solidify into gels to encapsulate printed cells.  Polypeptides are ideal materials for these so called bio-inks because of they can be designed with bioactive regions and can be biocompatible.  Using protein engineering, new materials will be designed and tested for properties essential for use as bio-inks.

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

While electron microscopies have emerged as one of the most versatile tools in instances when extreme spatial is required, their application is limited when the materials of interest are sensitive to electron beam damage. In these cases, in order to be imaged the samples have to undergo severe alterations including cryogenic or chemical fixation, to enable them to withstand the harsh conditions to which they are expose to while being imaged in electron microscopes. Besides being technically complex these methodologies also have the potential to irreversible distort the structure of the sample. The student involved in this research will develop alternative strategies enabling high resolution electron imaging of beam sensitive soft matter materials. He/she will work on: (i) the design and fabrication of imaging cells, in which the samples of interest are attached to a water impermeable, but electron beam transparent window; 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. The methods developed will allow the imaging of soft matter samples in their native environment while greatly reducing their beam exposure and associated beam induced damage [1]. These developments will be important for the characterization of systems such as polymeric microgels. Through the involvement in this research the student will become proficient in the use of surface characterization tools for morphological and chemical analysis. He/she will also become acquainted with a suite of computational methods widely used in image processing. Through this research the student will gain experience on the challenges and rewards of working on an interdisciplinary research project that merges the physics of soft matter system, electron microscopy characterization and image processing.

[1] “Sparsity based noise removal from low dose scanning electron microscopy images”, Proc. SPIE Electronic Imaging 9401, 940105-1 (2015).

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


Modeling Fluid Flow in Low Reynolds Number Systems
Dr. Miron Kaufman and Dr. Petru Fodor, Physics
1 Student

This analytical and numerical work is geared towards understanding the flow structures that form in low Reynolds number systems. These include: (i) cavity systems relevant in the design of polymer handling systems, such as single screw extruders that can be approximated as cavity systems with moving boundary conditions (walls) [1]; and (ii) mixing sections of microreactor devices [2]. In particular we are interested in the formation of eddies that can either impede or help the mixing process. One interesting problem in this respect is the assessment of the stability of these eddy structures under oscillatory conditions, either due to oscillations in the input flow or of the boundaries defining the systems investigated. The student involved in this project will learn the fundamentals of fluid dynamics and mixing and the relevance of these fields to practical applications. 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 thermodynamical analogies.

[1] “Moffatt Eddies in the Single Screw Extruder: Numerical and Analytical Study”, P.S. Fodor and M. Kaufman, AIP Proceedings 1664, 050010 (2015).

[2] “Improving fuel consumption in microfluidic based fuel cells”, J. D’Alessandro and P.S. Fodor, Fuel Cells 14, 818 (2014).

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


Microfluidic channels and mixers
Dr. Chandra Kothapalli, Chemical and Biomedical Engineering
1 Student

It has been well established that microfluidic platforms offer better versatility with varying channel dimensions and architecture, flexibility for introducing various compounds of interest, provision for in situ imaging and live-monitoring of experiments over long durations, and high-throughput and high-content imaging capabilities. In collaboration with Dr. Fodor, we are investigating how fluid flow and molecular diffusion evolves spatiotemporally within microfluidic channels, to enable design and implementation of better microfluidic mixers. During Summer ’17, an undergraduate student recruited to work on this project will be trained on various aspects of microfluidics, including design, fabrication and assembly of microfluidic devices from silicon wafer molds using soft-lithography techniques, and implementation of the devices by connecting to external fluid pumps. S/he will investigate the role of microfluidic channel design features on the effectiveness of mixing (i.e., mixing index) within the device.

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


Flowing past cilium
Dr. Andrew Resnick, Physics
1 – 2 Students

This project addresses several issues of central importance to kidney cystic disease. These include: how ciliated tissue responds to flow stimulation and how aberrant flow stimulation may induce a pro-cyst response in kidney epithelial tissue.  Our proposed studies will show how fluid flow, in itself, can regulate cell and tissue responses relevant to ADPKD.  The specific model system used here, a mouse ciliated kidney epithelial cell line, has been widely used to model polycystic kidney disease in humans. The ubiquitous existence of both primary cilium and fluid flow in other physiological systems ensures the results and conclusions will be broadly applicable and directly relevant to better understand the large class of disorders known as ciliopathies.

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


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

Microgels are water-filled nanoparticles made out of crosslinked chains of amphiphilic polymer. The amphiphilic nature of the parent polymer gives rise to microgels’ reversible volume phase transition. Microgels transition from large, soft particles of loosely bound polymer chains to smaller, more tightly packed polymer clusters8,9. Their size, shape, and swelling/deswelling ratio depend on environmental conditions and parameters of synthesis such as solution temperature, pH, salt concentration, polymer concentration and molecular weight, and cross-linking density. Careful choice of synthesis conditions allows control over the resulting particles, which is beneficial when considering microgels as potential vesicles for targeted drug delivery and bio-sensing agents. In addition, microgels are of great interest to fundamental science since they can be used as an experimental system to test theoretical models of statistical mechanics. In particular, Flory-Huggins free energy theory predicts the volume phase transition of cross-linked amphiphilic polymer chains; thus it can be tested with experimental data on microgels. In addition to studying the microgel volume phase transition, the coil-to-globule transition of un-cross-linked parent polymer chains can also be studied. A particular system of interest is the biocompatible and commonly available polysaccharide, hydroxylpropylcellulose (HPC). HPC microgels transition from a swollen state at room temperature to a de-swollen state above 410C. The microgel volume decreases by a factor of 3-20 under this transition depending on the synthesis conditions. One student on this project would learn the basics of polarized/depolarized dynamic and static light scattering spectroscopies and spectrophotometry techniques and would use them to study the structure, dynamics, and volume phase transitions of synthesized HPC microgels. A second student will focus on optimization of microgel synthesis and a systematic comparison of the phase transition behaviors of microgels and their parent polymer HPC, in their phase transition behavior as seen by spectrophotometry and light scattering. Both students will interact closely with Kaufman’s group to provide data for statistical physics modeling of the microgel phase transition and with Fodor’s lab for wet-sample electron imaging.

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


Total Internal Reflection Microscopy (TIRM) of Anisotropic Particles
Dr. Chris Wirth, Chemical and Biomedical Engineering
1 Student

Colloidal interactions operate on a ~kT energy scale over a ~1 - 100 nm length scale. Despite the small magnitude of forces governing colloidal interactions, they are essential to the microstructure of macroscopic materials. Total Internal Reflection Microscopy (TIRM) is capable of measuring these weak interactions via the collection of light scattered by a particle in an evanescent wave propagating along a surface. The primary advantage of TIRM over other techniques that measure surface interactions, such as Atomic Force Microscopy (AFM), is that TIRM operates on a thermal energy scale (i.e. ~ kT, k is Boltzmann’s constant), whereas AFM operate on a mechanical energy scale (i.e. ~ kSX2/2, kS is the cantilever spring constant). Unfortunately, current state-of-the art TIRM can only be conducted with spherical particles. This is a fundamental drawback for groups studying interactions among non-spherical colloidal particles, such as clay or red blood cells. In this project, we are seeking to fill this gap in knowledge by developing and implementing a novel technology consisting of digital video microscopy combined with evanescent wave scattering suitable for anisotropic particles. Initially, we will use the novel TIRM technique to investigate the surface force between a chemically anisotropic particle (i.e., Janus particle) and substrate. This initial work seeks to determine the extent of coupling of surface forces to the dynamics of a Janus particle. In future summers, the student’s work will be extended to determine how surface forces affect the dynamics of a “self-propelling” Janus particle. Extending the technique to particles of arbitrary shape would be a transformative step forward that will be valued by a vast audience of chemists, physicists, and engineers.

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

 

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