Acute respiratory failure affects the lives of over half a million patients each year, with significant mortality rates. While some patients can be treated using conventional respirators, which ventilate the injured lungs, many patients cannot. Providing breathing support independent of the lungs is the principal focus of Dr. Federspiel's research group in the Artificial Lung Laboratory of the McGowan Center for Artificial Organ Development. His group is developing next generation artificial lungs or blood oxygenators, including small implantable devices for temporary support and wearable devices for longer-term support.
The laboratory's flagship project is the Hattler Catheter, a unique artificial lung inserted as a venous catheter to provide temporary breathing for patients with acute lung failure. The Hattler Catheter project and other related projects in the Artificial Lung Lab focus on novel techniques for improving mass transfer in artificial lungs, so that more gas transfer can be achieved with smaller devices. Enhanced mass transfer is not only a key to implantable oxygenators, where anatomy can impose significant constraints, but is also pertinent to next generation, wearable artificial lungs.
Diabetes mellitus is the single most costly chronic disease in the United States. The key to treating the insulin-dependent form of the disease is to control blood glucose within a fairly narrow range. One approach is to remove the patient from the insulin administration "control loop", and use instead an implantable insulin delivery device containing three primary components: a glucose sensor, a pump mechanism, and a computer algorithm which calculates an insulin delivery rate from a glucose measurement.
The synthesis of this computer algorithm is a focus of Professor Parker's group. By developing a mathematical model of the type I diabetic patient, potential therapeutic strategies can be efficiently tested in silico, as opposed to the expensive alternative of preliminary animal and patient testing. An additional benefit is the ability to test various glucose control algorithms on a "simulated population" to test the effects of inter- and intrapatient uncertainty on the controller performance.
Simulation results for an individualized therapy (controller tuned for the specific patient) have demonstrated glucose control superior to that achieved by the pancreas in the healthy human patient. When tested on a simulated population that encompassed significant interpatient variability, the glucose levels were maintained within the desired normoglycemic range. From these exciting results, a device based on this algorithm is now ready for animal trials.
Scientists have for many years been attempting to utilize enzyme catalysis outside the cellular environment. Some of the more successful endeavors include enzymatic laundry detergents, contact lens cleaning solutions, and food processing. However, when one considers the number of different types of reactions that are enzyme catalyzed, it is striking that so few commercial examples can be cited. Brief catalytic lifetimes, environmental and thermal sensitivity, a lack for re-usability, and general applicability issues limit the utility of many enzymes.
Technological developments that address each of these shortcomings have opened a new paradigm for industrial catalysis. Using catalytic polymers that are synthesized by combining a relatively hydrophilic polyurethane prepolymer and an aqueous solution, we have been able to prepare a unique urethane foam. Control of the porosity and physical properties of the polymer is facilitated by introducing additives such as surfactants. The entire synthetic process is complete in approximately 10 minutes.
State-of-the-art facilities and instrumentation range from a one-gallon, see-through, high-pressure, high-temperature agitated autoclave, to a 10-ft high, 1-ft diameter, high-pressure, high-temperature slurry bubble column reactor. The reactor working pressure is 825 psig at a temperature of 600 degrees Fahrenheit. The reactor is completely insulated and is provided with a gas sparger, heating and cooling systems, two Jerguson sight-windows, mass/density flow controllers, differential pressure cells, pressure transducers, and thermocouples.
Research by Professor d'Itri and her colleagues has developed improved design criteria for catalysts. As an example, they have defined how the activity and the selectivity of a (Pt+Cu)/SiO2 catalyst is affected by composition in the reaction of 1,2 dichloroethane dechlorination in a H2 containing atmosphere.
The studies showed that for monometallic Pt catalysts, and those with Pt/Cu atomic ratio > 1, the reaction products are primarily ethane and monochloroethane. However, decreasing the Pt/Cu ratio increase the selectivity towards ethylene. A selectivity towards ethylene of nearly 90% is obtained for catalysts with a Pt/Cu ratio 1/3. Using infrared analysis of CO adsorption, it was shown that Pt and Cu form bimetallic particles during pretreatment and in addition to the dilution effect, Cu changes the electronic properties of the Pt atoms.
Professor Eric Beckman and Professor Robert Enick have invested techniques to gel carbon dioxide. Their CO2 gelling technique requires less expensive, non-fluorinated compounds. The benefits are reduced costs and an environmentally attractive process.
The potential applications for this unique development include:
• Thickened CO2 to enhance the tertiary recovery of petroleum from aging oil fields
• Because of the viscosity of "natural CO2", the fluid dispersion in a reservoir is difficult to control. Increasing the viscosity of the CO2 offers the potential to significantly improve the well stimulation.
• Since the CO2 is environmentally benign, thickened CO2 is very attractive for reducing the environmental impact of well stimulation procedures.
• The CO2 gels produced can be precursors to microcellular materials, and could also support CO2-based coating processes.
A current focus is on the utilization of these technologies for environmentally benign gas and oil well operations.
Liquid and supercritical carbon dioxide have attracted much interest as environmentally benign solvents, but their practical use has been limited by the need for high CO2 pressures to dissolve even small amounts of polar, amphiphilic, organometallic, or high-molecular-mass compounds.
So-called "CO2-philes" efficiently transport insoluble or poorly soluble materials into CO2 solvent, resulting in the development of a broad range of CO2-based processes. But as the most effective CO2-philes are expensive fluorocarbons, such as poly(perfluoroether), the commercialization of otherwise promising CO2-based processes has met with only limited success.
Professor Beckman and his colleagues have shown that copolymers can act as efficient, non-fluorous CO2-philes if their constituent monomers are chosen to optimize the balance between the enthalpy and entropy of solute-copolymer and copolymer0copolymer interactions. Guided by heuristic rules regarding these interactions, we have used inexpensive propylene and CO2 to synthesize a series of poly(ether-carbonate) copolymers that readily dissolve in CO2 at low pressures. Professor Beckman notes that "we expect that our design principles can be used to create a wide range of non-fluorous CO2-philes from low-cost raw materials, thus rendering a variety of CO2-based processes economically favorable, particularly in cases where recycling of CO2-philes is difficult."
Dr. Enick and his colleagues have perfected the use of an invisible fluorinated coin conservation solution that molecularly bonds to the coin metal and locks in the condition of the coins at the time the solution is applied.
The application of the solution prevents the coins from toning. The application technique involves placing a one-molecule thick coating, referred to as a self-assembled monolayer (SAM) on the coin. The coating can be sprayed on or applied through immersion in the solution.
There are several distinctions between the SAM and conventional polymer or lacquer coin coatings. Lacquer is a transparent coating one-tenth millimeter thick that is visible to the naked eye and is susceptible to cracking, flaking and discoloration when it ages. Because the SAM is actually thinner than a wavelength of light, it is invisible. The SAM will also not peel, crack or discolor, and is more resilient than lacquer because the SAM chemically bonds to the coin surface.
Conventional thiols have a pungent and dangerous odor. For the coin conservation treatment, fluoroalkyl amide thiols (FAT), which emit no detectable or dangerous odor, are employed. The fluorocarbon in the compound is similar in composition to Teflon; the amide groups are capable of attracting the amide group of the adjacent thiol molecule through hydrogen-bonding and the sulfur bonds to the metal.
Polyurethanes offer extraordinary versatility and are used in many applications including: thermoplastics for automotive applications, organic and water-borne coatings, foams for seat cushions and insulation, fibers, thermoplastic elastomers (Lycra, etc.), and thermosets. Professor Beckman, in collaboration with Professor Agarwal (School of Dentistry) has generated novel, non-toxic, biodegradable peptide-based urethane polymers that have been successfully evaluated using rabbit bone marrow cells. These polyurethane foams, made from lysine, glycerol, sugar, and tyrosine, support the growth of osteoblasts and biodegrade over a period of time to non-toxic materials. These materials are showing promise as bone-tissue engineering scaffolds. These findings are an exciting precursor to the use of these innovative materials in human reconstructive surgical procedures.
Carbon nanotubes are microscopic structures composed of graphite-like carbon rolled into hollow tubes with diameters on the order of one nanometer. These nanotubes have remarkable electronic and mechanical properties, as shown by experiment and theoretical calculations. The unique properties of nanotubes make them promising candidates for a variety of applications, such as single-molecule transistors, nanowires, chemical sensors, novel catalytic supports, components in nano-engineered machines, fibers for nanocomposite materials, and molecular sieves for gas storage and separations.
Professor Johnson is investigation the properties of carbon nanotubes and exploring their usefulness through molecular simulation and electronic structure calculations. He is currently working on chemical and physical storage of hydrogen on idealized and more realistic models of nanotubes. His interests also include gas separations, quantum confinement, chemical reactions inside nanotubes, metal-nanotube interactions, the effect of defect sites on the electronic properties of nanotubes, and the use of nanotubes in catalysis.
Granular materials exhibit a vast array of unusual phenomena-spontaneous segregation, pattern formation, etc,-and have been a traditional bottleneck in numerous industries. A primary cause of much of their unique behavior can be traced to the nature of particle-particle interactions, which introduce new forces and length scales which may create difficulty for continuum modeling of these systems.
New discrete, multi-physic, modeling tools developed in Professor McCarthy's group show promise for bridging the gape between the micro-scale (particle-scale) and the meso-scale (pilot-scale).
Using these tools, they find that the ubiquitous contact and stress heterogeneities in particulate systems-caused by stress "chains"-may serve as the nucleus of hot spots in solid-catalyzed reactors or stored granular material. Also, recent work has been done that calls into question the old adage that cohesion limits segregation.
Adding solid rods measuring just a few billionths of a meter long to polymers can dramatically improve the mechanical, thermal, and electrical properties of the mixture. Research by Professor Balazs in collaboration with Professor Jasnow, of Pitt's physics and astronomy department, used two-dimensional simulations to examine how the tiny rods interacted in mixtures of two polymers.
Their findings could lead to faster and easier production of electrically conducting pathways in insulating materials or to the creation of reinforcing structures in organic/inorganic composites. The researchers found that nanotubes embedded in the polymers that naturally repel one another can align end-to-end, creating possible electrical pathways in the mixture. Rod-like nanoparticles naturally arrange themselves into percolating networks that strengthen the polymer blend to which they are added.
"The rods themselves are small-a few billionths of a meter-but the networks extend throughout the material," said Balazs. The individual rods are on the nanometer scale, but self-assembled into the network, they extend throughout the material. In that sense, they are very large.
These findings should assist in developing new materials. Most promising, say Balazs and Jasnow, are applications in the automotive industry, where the electrical pathways created by nanotubes could be used to create more efficient batters, and strong polymers could be fabricated into lightweight parts for automobile bodies and chassis.