Abstracts from the College of Engineering
Undergraduate Summer Research Symposium August 10, 2005

Ordered alphabetically by student's last name

Bending Mechanics of a Linear Colloidal Aggregate

Drew Amis and Eric M.  Furst
Department of Chemical Engineering
The bending mechanics of an elastic linear aggregate consisting of spherical particles of poly(methyl methacrylate) (PMMA) was using finite element analysis.  By properly defining the aggregate geometry, PMMA elastic properties, and specifying boundary conditions, the deflection of aggregates was calculated.  Both two and three-dimensional models of the aggregate were analyzed with a finite contact region between adjacent particles.  While one end of the aggregate was defined to be stationary in all directions, varying loads were applied to the other end, yielding corresponding vertical displacement values.  In order to understand the effect of contact regions on the bending of aggregates, first, models with different contact radii were analyzed.  After obtaining the data for the aggregate, it was compared to the theoretical bending rod equation, which represents vertical displacement as a function of the position of each particle’s center of mass.  By fitting the numerical data to the bending rod equation, the contact radius can be determined algebraically and compared to the originally defined contact radius.  After making this comparison, the numerical data for a two-dimensional model shows excellent agreement with the bending rod equation, while the three-dimensional model data only shows good agreement for small loads.  In addition, stress contour plots of the aggregates were created to understand how different forces were distributed at the interfaces of adjacent particles. 

Kinetics and Thermodynamic Equilibria of Precipitation and Crystalization of Lysozyme

Aaron Chockla, Yu-Chia Cheng, Abraham Lenhoff
Department of Chemical Engineering

The design and optimization of protein separation processes such as crystallization rely heavily on empirical methods to design and optimize.  The general goal of this project is to characterize the phase behavior of proteins in concentrated salt solution.  A specific objective is to characterize the dense amorphous protein phase that forms at high ionic strengths through measurements of dissolution rates of the precipitate.  The initial data collected for this project follow the expected trends reasonably well, showing that with increasing ionic strength with constant initial protein concentration, both the induction time and final protein concentration is reduced.  Also, as initial protein concentration increases at constant ionic strength, the induction time decreases while the final protein concentration remains constant.  Given these results, the next course of action is to vary the precipitating agent, or salt used to control the ionic strength, pH and protein.  This will help confirm or disprove the developing theories. Funded by the HHMI Undergraduate Science Education Program.

Particle Separations in Microfluidic Channels

Jonathan Edwards, Steven Kestel, and Eric M. Furst
Department of Chemical Engineering
Microfluidics is an emerging field in both chemical and biological analysis, and in chemical production.  Commonly, microfluidic devices are characterized by tiny channels which direct minute quantities of fluid.  This project focused on particle separations in microfluidic systems.  Optical traps, or “laser tweezers”, create a gradient force which is capable of holding a colloidal particle in place.  Arrays of optical traps were then used to conduct sized-based separations of particles.  For instance, when a solution of one and three micron particles flows through the traps, the three micron particles are trapped while the one micron particles pass through.  To construct the microfluidic channels, a rapid and inexpensive process called soft lithography was employed.  Next, to form the optical trap arrays, a 1064 nm Nd: YAG laser was scanned from trap to trap.  For this project, hexagonal trap arrays were formed.  Several parameters which govern these separations were investigated, including laser power, fluid velocity, trap array geometry, and particle size ratios.  Also, the effect of particle size on retention time and the collision interaction between particles was characterized.  Applications of microfluidic particle separations include cell sorting and solid-phase bioassays.    


In-vivo glucose sensor using Poly(vinyl alcohol)/Sodium Tetraborate Decahydrate (Borax) Network

Nikki Ennis and Annette Shine
Department of Chemical Engineering

A wireless in vivo glucose sensor would be very beneficial to diabetics, eliminating the discomfort of constant pinpricks. A proposed sensor consists of a magnetic strip surrounded by a polymer network, which has hydroxyl groups cross-linked with borate ions. Disruption of these cross-links by glucose is are quantifiable by measuring the rheology of the network via resonant frequency spectrum of the implanted sensor. The goal of this research is to design the polymer system that responds to glucose concentrations in the physiological range by optimizing the members of hydroxyl and boronic acid groups. A model system of poly (vinyl alcohol) (PVOH) and borax was used, which forms a gelled network. Dynamic shear rheology measurements were taken on a modular compact rheometer with a cone and plate fixture. Frequency sweeps were run from 0.1 to 100 1/s at strains of 0.3%, which amplitude sweeps confirmed were in the linear range. This low frequency range gave molecular insight about the polymer network. The viscoelastic storage modulus, G’, and the loss modulus, G”, both increased when the concentrations of PVOH and Borax were increased. In the presence of 180.5mg/dL glucose, both G’ and G” decreased by about a factor of 2. The frequency dependence of G’ and G” showed Maxwell-like behavior, with a relaxation time of about .3s (1.8wt%PVOH gel). This indicates that network elasticity, rather than viscosity, would dominate at the higher resonant frequency of the magnetic sensor. Funded by the HHMI Undergraduate Science Education Program.

Tracer Particle Interactions with a Beta-Hairpin Hydrogel

Becky Gable, Cecile Veerman and Eric M. Furst
Chemical Engineering, University of Delaware

Hydrogels have promising applications in tissue engineering and drug delivery. MAX1 is an amphiphilic peptide which self-assembles into a hydrogel network upon changes in the solution conditions, such as pH or ionic strength. Knowledge of the interactions between hydrogels and embedded particles with unique sizes and surface chemistries is crucial in understanding and optimizing hydrogel functionality. Interactions between MAX1 and fluorescent tracer particles were characterized through multiple particle tracking, isothermal titration calorimetry (ITC), and bulk rheological measurements. Multiple particle tracking was used to monitor the MAX1 hydrogel self-assembly process over time. Tracer particle movement decreased with increasing time after the initiation of self-assembly. However, peptide adsorption to the tracer particles was indicated by anomalous mean-squared displacements versus lag time curves which did not fall on a master curve for polystyrene and carboxylated polystyrene particles of various sizes. ITC confirmed differences in peptide adsorption for polystyrene, carboxylated polystyrene, amine-modified polystyrene, and polyethylene glycol (PEG) coated polystyrene particles due to unique surface chemistries. However, similar gel strengths for MAX1 with and without the various particles were observed using dynamic bulk rheological measurements. A proposed model hypothesizes that surface chemistry differences affect the particle stability within the MAX1 medium through its interactions with the hydrogel network. From these characterizations of the interactions between MAX1 and various tracer particle sizes and surface chemistries, MAX1’s potential in tissue engineering and drug delivery applications proves promising. Funded by the HHMI Undergraduate Science Education Program.


Kinetics and Thermodynamics of Recombinant Bovine Granulocyte Colony Stimulating Factor (bG-CSF) Aggregation

Justin Quon, Jennifer Andrews, Professor Christopher Roberts
Department of Chemical Engineering

Abstract withheld by request
Funded by the HHMI Undergraduate Science Education Program.


Laser Tweezer Measurements of Colloidal Interactions in Viscoelastic Fluids

Matthew Rosborough, Alex Meyer, and Eric M. Furst
Department of Chemical Engineering

Viscoelastic fluids, which exhibit both viscous and elastic behavior during deformation, cause suspended particles to aggregate into linear structures when the fluid is sheared.  In addition, these linear aggregates are aligned in the direction of the shear flow.  The interparticle hydrodynamic forces underlying this aggregation were measured using video microscopy combined with laser tweezers and image analysis.  The purpose for measuring these colloidal interactions was to characterize the forces behind the aggregations so that particle-filled polymer solutions could be engineered for further applications.  2.005 wt% aqueous polyethylene oxide (PEO) was chosen for the experiments due to the fact that it shear thins; the colloidal particles filling the polymer solution were monodisperse polystyrene (PS) microspheres with 3m diameters.  Experiments in which two PS particles were trapped at various angles with respect to the direction of the flow were performed in aqueous PEO.  The controls for these experiments were solutions of the same particles suspended in water.  Comparison between the viscoelastic fluid experiment and the Newtonian fluid experiment data allowed for the observation of slight string-aggregation forces on the order of picoNewtons.  Future work will include experimentation with better shear-thinning fluids and macrorheology for more comparison purposes.  This work is funded through the Science and Engineering Scholars Research Program.

BioExplorer – An Immersive Tool for the real-time Exploration of three-dimensional Biomedical Datasets

Patrick Ruff and Karl V. Steiner1
Department of Computer and Information Sciences and Department of Biological Sciences, and  1ECE and Delaware Biotechnology Institute

The rapid advances of computer technology and virtual reality are beginning to make it feasible to develop cost-effective real-time tools to explore biomedical simulators that can be used for training and surgery planning purposes. The goal of this research internship was to add additional features to a larger existing code, called BioExplorer.  This program was developed at DBI over the past two years to allow the user to fly through a three-dimensional rendering of organs within the human body within an immersive, computer aided virtual environment (CAVE).  The existing version of BioExplorer facilitated the fly-through mode and several simple methods of interaction with the loaded datasets.  While these existing features were an improvement over looking at two-dimensional CT scans, there are considerable opportunity for further development and implementation of new tools and capabilities. A study of the existing BioExplorer code, the IRIS Performer OpenGL manual, and the archived Performer online mailing lists provided an understanding of the basics behind the complex programming concepts within an immersive CAVE environment.  Several new features were implemented during this internship.  These new features include the ability to change the color of the organ, the ability to change where the light sources and direction for the scene graph, the ability to change the interactive wand between a pointer, a scalpel or a ruler, the ability to save and load the state of the 3D environment (object position, light position, colors, transparency, etc.), and the ability to measure interactively between features in the scene graph.  These contributions have clearly expanded of the BioExplorer capabilities. In the future, several new features will probably be added including  haptic robot force-feedback, as well as a meter that lets you know your relative location inside 3D space. Supported by the NIH NCRR - Delaware INBRE grant, grant number 2P2QRR016472-04

A Comparison of Nanotube Sheets Fabricated Using Single Wall and Multi-Wall Carbon Nanotubes

Jachin Spencer1, Sonam Gupta2, Lee Stein2, Shaoxin Lu2, and Balaji Panchapakesan2
1 Department of Electrical Engineering, Delaware Technical and Community College
2Department of Electrical and Computer Engineering,University of Delaware, Newark, DE 19716

The carbon nanotube is a versatile nanostructure.  One application of carbon nanotubes are they can be used to create sheets of nanotubes for more practical macro-, micro- and nano-scale applications. Although individual nanotubes show unique electrical, extraordinary mechanical properties, these nanotubes are often difficult to manipulate at the nano-scale. For more practical macro-scale applications, one needs to create sheets of nanotubes that can possess exceptional strength and flexibility. The project goal is to look at the differences between thin sheets created using single walled and multi-walled nanotube films.  Thin sheets were created using single walled carbon nanotubes and multi-walled carbon nanotubes that were dispersed in isopropyl alcohol solution.  The two types of sheets were created for each type of nanotubes, a free standing "thick" sheet, and a non free-standing thin sheet.  The sheets were created using vacuum filtration, and sheet thick ness was controlled using the solution concentration.  Electron microscopy was used to examine the sheet uniformity. High quality sheets as thin as 1 m and about 2.5 cm diameter can be fabricated using this versatile technique. Sheets of single and multiwall carbon nanotubes can now be used for applications such as sensors and actuators by patterning structures directly on nanotube sheets.  Funding Source:  Bridges program DTCC

Links: Summer 2005 Undergraduate Research Symposium, Symposium Abstracts from other Colleges and Departments,
Undergraduate Research Summer Enrichment ProgramUnversity of Delaware Undergraduate Research Program, Howard Hughes Undergraduate Program.
Created  4 August 2005. Last up dated 13 August 2005 by Hal White
Copyright 2005, University of Delaware