Undergraduate Research with Dr. David Tomasko
Thermodynamics, Separations, and Materials Processing

General Research Description
Current Projects
Undergraduate Contributions
Future Undergraduate Projects
Undergraduate Qualifications
Contacts & Links

General Research Description
Supercritical CO₂, which is CO₂ above its critical temperature (31.1^oC) and critical pressure (73 atm), can be used in place of many organic solvents. The advantage of using supercritical CO₂ is that it is non-toxic, non-flammable, inexpensive, and widely available. The most widely known current commercial application to use this technology is extraction of caffeine from coffee beans to make decaffeinated coffee.

However, our research group focuses more on the applications linked to polymeric products. One large potential commercial application of this technology in association with polymers is to replace ozone depleting CFCs in the manufacturing of structural foam insulation. Some other more interesting applications deal with loading biological molecules into polymer matrices for use as either artificial human tissue scaffolds or drug delivery devices. Nanotechnology is also a hot topic and we are working on molding and bonding of polymers at the nanoscale also using supercritical CO₂ as a molecular softening agent or “glue”, respectively.

Current Projects
Formation of micron sized insulin particles – Diabetes is a widespread disease and people that currently suffer from it must control their blood sugar levels by intravenously injecting insulin. This process is painful and disliked by many patients. If insulin particles can be made small enough (< 5mm) patients could then use an inhalation device to simply and painlessly inhale the drug. We are working to make these particles by first dissolving the drug in an appropriate solvent and then concurrently spraying this into a high pressure cell filled with supercritical CO₂, which acts as an anti-solvent and causes the insulin to dry and create the desired particles.

Measuring the adsorption of CO₂ on nanoparticles – Nanoparticles, such as nanoclay and carbon nanofibers, are mixed in with polymers, at low concentration, in order to improve the mechanical properties of the pure polymer. Some properties that are improved are mechanical strength, molecular diffusion barrier properties, and acoustic dampening. These nanocomposites, the mixture of nanoparticles with polymers, can also be foamed by the process of extrusion using CO₂ as the gas to foam them. The amount of CO₂ that adsorbed onto the nanoparticles compared to the amount that absorbs into the polymer matrix is useful in predicting the final characteristics of the foam product. So, CO₂ in placed in contact with the nanoparticles and the mass increase is observed using a very sensitive balance.

Mixing drug and polymer in an extruder for drug delivery – Extrusion is a continuous process where polymer is melted, mixed, and conveyed between heated, rotating metal screw(s) and a heated barrel. The molten polymer is then forced out of a die with a defined shape. If high pressure CO₂ is added into the extruder it causes the polymer viscosity to decrease and allows us to reduce the temperature before adding in a temperature sensitive drug compound.  In addition, CO₂ produces polymer foam as it is expelled from the die and creates an easily milled material for further processing into tablets.

Undergraduate Contributions
Our group typically has at least two undergraduate students working at any given time. We have had many outstanding undergraduate research projects and look forward to having more. Listed below are a couple of the most recent projects.  All undergraduates are expected to present their work at the Denman forum. 

Mike Noon used a barometric method to measure solubility of CO₂ in poly(methyl methacrylate) (PMMA) and polystyrene (PS) near its critical point. This is an interesting region on the phase diagram due to the large compressibility of fluids near their critical point and the associated anomalies in solubility that also occur.

Maren Siebold used a high pressure/temperature mixer to create solid dispersions of 4-amino salicylic acid (4-ASA) in a biologically friendly polymer named Eudragit. These solid dispersions can be formulated in different geometries and concentrations in order to create polymer based pills that get released into the body upon oral delivery at the proper dosage and release rate.

Future Undergraduate Projects
These projects are just ideas and could be modified or whole new project could be thought up based on the interests of the student. One potential project will deal with immobilizing active biological enzymes on a polymer surface through supercritical CO₂ modification. These enzymes will then be tested to ensure their biological activity is maintained after processing. The immobilization technology gained will then be applied to the channels of nanofluidic diagnostic biomedical devices. Another potential project will deal with using CO₂ to mold and bond polymers on the nanoscale for use as nanofluidic devices or tissue scaffolds.

Funding is not currently available; thus research positions are for course credit or volunteer only. Tomasko will accept thesis and non-thesis students at this time.

Undergraduate Qualifications
There are no strict qualifications except that you should be prepared to spend at least 10 hours per week on research.  GPA: 3.0 or higher
Necessary courses: No stringent requirements, though a background in polymer science would be helpful

Contacts & Links

Research Group

Faculty Profile

Email at: tomasko.1@osu.edu