Dr. Kiran with his device

Fluids and Polymers: A Supercritical Breakthrough

By:  Zeyad Zeitoun

As we gain knowledge in a myriad of scientific fields, we find that the way in which we perceive the world can be flawed. The models we develop to decipher the phenomena occurring around us sometimes deceive us until we uncover a piece of evidence that shifts our perspective in another direction. “Nature doesn’t lie, but our thinking may be wrong,” declares Dr. Erdogan Kiran, a renowned Chemical Engineering professor from Virginia Tech. Dr. Kiran is well aware of the errors we make in our thinking, and kept this in mind when he began conducting his research within a genuinely unique field at the University of Maine decades ago.

Chemists and Chemical Engineers regularly attempt to shed light onto the properties of fluids – the scientific category for liquids and gases. After experimenting with these substances, researchers encountered a phenomenon in the thermodynamics of fluids called the supercritical condition. Once a fluid exceeds a certain pressure or temperature, its physical structure reaches a domain in which you can no longer make a distinction of which phase the fluid is in; one can not tell whether the fluid is a liquid or a gas at that point in time, as its properties rest somewhere in between the two. A supercritical fluid can seep through solids like a gas while simultaneously dissolving the solid like a liquid would. These conditions naturally arise and supercritical fluids play an important role in nature in many geological processes. At the deepest levels of the oceans there exist underwater volcanoes with booming vents that jet out massive amounts of hot water at the supercritical condition due to the extremely high pressures and temperatures.

After obtaining his Ph.D. in Chemical Engineering at Princeton University, Dr. Kiran began focusing his research on polymers. He recognized that studying supercritical fluids held high potential in polymer synthesis, modification and processing techniques. Little did he know that the work he would do would not only expand the sphere of knowledge in this field, but also carry a distinct effect on the scientific community in which he operates. His analysis of the behavior of mixtures of carbon dioxide led to the realization that the fluid can be modified to make it more suitable for a given application. This common gas can be very useful in the separations of various chemicals, as it reaches supercritical conditions at relatively low temperatures and pressures. Furthermore, its physical properties, such as density, can be easily manipulated. An example of its usage is in the decaffeination of coffee beans. In the past methylene chloride was used to remove the caffeine from common coffee beans but would leave solvent residue, which is a potential health risk. Using supercritical carbon dioxide for the process is cleaner and leaves no toxic solvent residue behind.

Generating pressures similar to those at the bottom of the Atlantic Ocean is no easy task. At Virginia Tech’s Goodwin Hall, Dr. Kiran oversees a lab containing several specially designed apparatuses dedicated to the analysis and utilization of supercritical fluids. His experimental systems are unique and look aesthetically futuristic in their setup. Some of his systems operate at pressures up to 15,000 pounds per square inch, almost 1000 times the regular pressure of air in the atmosphere. Special sapphire windows mounted on the vessels allow for direct observation of the fluids at these extreme pressures. The repercussions of building such high-pressure devices are potentially explosive, but the research team works with relatively small volumes (typically less than 100mL) and has taken all the necessary precautions to ensure no dangerous situation is ever reached. As Dr. Kiran cranks the pressure generator and the reading jumps hundreds of units every second, one can peer into these chambers across the sapphire windows with awe as mixtures transform into completely homogenous solutions at higher pressures. The live readings allow Kiran’s team to assemble various conclusions to widen the breadth of understanding of the behavior of polymers in these fluids at such conditions.

Dr. Kiran
Dr. Kiran describes the data collection system he has assembled in Goodwin hall. Dozens of cables and connections allow for a live reading of the pressurized tank pictured at the bottom of the image.

Over the past decades, Dr. Kiran has led a research program to not only continue advancing our understanding of these phenomena, but also to allow students to create pathways for their own aspirations. Dozens of students have entered and left the program to collaborate with and assist Dr. Kiran in his research to help procure novel interpretation of the data being collected. He seeks students with a desire to douse their curiosity and a motivation to boost their own level of knowledge. His research projects are supported by the National Science Foundation and Industry, which allows for open modification of experimental techniques. Kiran’s resources provide a gateway for the participants to create a real tool to generate actual, visible data. This can forge a tremendous level of confidence and excitement in the students, which can be pivotal in the future of these young scientists and engineers. On top of the research program itself, Dr. Kiran has also overseen summer courses in this field for hundreds of students from around the globe. Their participation has led to grand success, with many of the students currently occupying leadership roles in universities as well as commanding positions in related stretches of research.

Dr. Kiran is the founding Editor and Editor-in-Chief of the Journal of Supercritical Fluids, the only scientific journal of its kind specifically dedicated to the field of supercritical fluids and their functions. He also developed and edited the Elsevier book series on Supercritical Fluid Science and Technology, for which six books have already appeared since 2011. The former MIT, Cornell, and Princeton man is also quite alive in the scientific societies and has taken part in many international meetings and forums on the topic. Although his endeavors have already amassed immense conclusions about fluid phenomena, he knows we are yet to fully encapsulate the possible applications in polymer formation and biomedical processes. Dr. Kiran hopes to continue breaking ground at his Goodwin high-pressure lab, and it would not be surprising if he uncovers even more in the future.