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In Honor of John L. Anderson On August 1, 2007, John Leonard Anderson became President of Illinois Institute of Technology, culminating a distinguished career dedicated to scholarship, education, and leadership. At this time, he also concluded over 20 years as Associate Editor of this journal. I am very pleased to count him as a close friend. I first met John in 1976 when Carnegie Mellon tried to hire him from Cornell, where he had been Assistant Professor of Chemical Engineering for about five years. We spent far less money on recruiting then: during John’s second visit, he stayed at my apartment rather than a hotel. I was a second-year Assistant Professor. Despite this, we succeeded in attracting to Carnegie Mellon one of our most successful faculty members. John quickly rose though the academic ranks at Carnegie Mellon, serving as Director of the Biomedical Engineering Program(1980-1985),HeadofChemicalEngineering(1983-1994), and, finally, Dean of Engineering (1996-2004). One of his lasting accomplishments as Dean was the establishment of Biomedical Engineering as a department. Membrane Transport As a graduate student at Illinois, his mentor was John A. Quinn (now at Penn). At Illinois, John learned how to make track-etched pores in mica sheets. These long uniform nanop-
ores, the number and size of which can be independently controlled, produce highly ideal model membranes, which have served as the vehicle for much of John’s research in membrane transport of electrolytes, colloidal particles, and polymers. John and his students used these membranes to study how pore size and charge affect the diffusion of large moleculesslatex spheres, flexible polymers, asphaltenessin confined spaces. One of his membrane projects involved the hydrodynamic thickness of polymer layers adsorbed to the pore walls. From the increase in the ratio of pressure drop to flow rate through the membrane, the thickness can be inferred. Even with monodisperse polymers, adsorption entails a random distribution of lengths for loops, trains, and tails. John and his students established that the hydrodynamic thickness is associated with the longest protruding tailseven a few of these tails have a profound influence on the hydrodynamics near the pore wall. Diffusiophoresis In 1980, our research paths began to cross. My first Ph.D. student and I determined the mechanism for a commercial process for electroless deposition of latex from an acidic solution onto steel. We found that an electric field was induced by the multicomponent diffusion of ions that accompanied the brief
10.1021/ie900013t CCC: $40.75 2009 American Chemical Society Published on Web 02/25/2009
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acid attack of the steel during immersion; electrophoresis of the charged latex particles in the induced electric field controlled the rate of deposition. I was quite excited because I thought we had discovered something new. John pointed out that that the mechanism I described was nothing more than diffusiophoresis, which was reported by the Russian scientist Boris Derjaguin over 30 years before. In the decade that followed, John and I coadvised two Ph.D. students and published a series of theoretical and experimental papers on diffusiophoresis. For most electrolytes, we showed that electrophoresis in the induced electric field was the dominant contribution. However, gradients of KCl are wellknown to produce no significant electric field; yet, theory predicted that charged latex particles should migrate toward higher concentrations of KCl, albeit at a much lower speed than in other saltssso low as to be comparable to the Brownian motion of latex in our usual experiments. So John conceived a clever experiment to demonstrate diffusiophoresis in KCl gradients. Starting with equal concentrations of latex but unequal concentrations of KCl on either side of a membranespermeable to both salt and latexswe observed that the latex concentration monotonically increased on the side of the membrane that had the higher KCl concentration. Because this increase could not happen by Brownian motion, and because no diffusion potential was detected across the membrane, we unambiguously verified the existence of diffusiophoresis in KCl without an accompanying electric field. One hallmark of John’s research, illustrated in this example, is the almost-equal blend of good experiments with good theory. Our theory also predicted that gradients of nonelectrolytes that have a tendency to adsorb onto the particles should also propel the particles toward higher concentration. Our experiments with nonelectrolytes were suggestive of diffusiophoresis but not compelling. Despite much effort being spent on the attempt, John refused to submit the results for publication because they did not clearly prove diffusiophoresis in nonelectrolytes. Although the results are described in the student’s Ph.D. dissertation, they were never otherwise published. This episode clearly indicates the very high standards to which John held himself in research. Later, in 1989, Staffeld and Quinn demonstrated diffusiophoresis by nonelectrolytes using a different solute from the one that we tried. 2-D Crystallization of Colloids As Dean of Engineering, John continued to keep active in research by coadvising Ph.D. students with Steve Garoff (Department of Physics) and Paul Sides (Department of Chemical Engineering). Through interaction with Dr. Marcel Bo¨hmer (Philips Electronics), John became interested in the twodimensional (2-D) aggregation of colloidal particles near the surface of planar electrodes. An electric field applied normal to a planar electrode causes charged particles levitated near the electrode to move laterally on the surface. While it is not surprising that a normal component of the electric field would exert a force on charged particles that is normal to the plane, why do the particles instead move in a perpendicular direction tangent to the plane? John and his colleagues determined that the electric field generates
an electro-osmotic flow around the charged sphere: fluid on the side of the sphere opposite the electrode flows away from the electrode along a closed streamline, which returns to the sphere along the surface of the electrode. Other spheres (regardless of their charge) become entrained in this flow and are brought toward the targent sphere. This is the mechanism for aggregation in direct-current (DC) electric fields. His research was recognized by the American Institute of Chemical Engineers (AIChE) in 1989, when John received the Professional Progress Award, as well as many special lectureships over the years. In 1992, John was elected to the National Academy of Engineering, and, in 2005, he became a Fellow of the American Academy of Arts and Sciences. Education John’s first sabbatical in 1982-1983 was supported by a Guggenheim Fellowship. Nevertheless, John taught a special topics course because, as he said, you are not really a member of a university unless you are teaching students. During these years, John was also very active in intramural sports, playing on the Chemical Engineering graduate student teams in softball, basketball, and football. Later, as department head, John and his wife Pat hosted an annual ski trip for graduate students and faculty at their vacation home in Hidden Valley. Like the weekly happy hours, this event was a most pleasant way to encourage interaction between faculty and students. Leadership At Carnegie Mellon, John held leadship positions as Head of Chemical Engineering and Dean of Engineering. In 2004, he became Provost and University Vice President at Case Western Reserve, and, in 2007, he became President at Illinois Institute of Technology. Most of this while serving as Associate Editor of this journal. What traits distinguish such a leader from the rest of us? Having shared many out-of-town trips and weekend vacations with John, I feel I know him well enough to attempt an answer, which is suggested by the following anecdote: While sharing dinner a few months ago, the topic of awards came up. Faced with several nominees with similarly strong attributes, it is tempting to divide the award among them. John stated emphatically that it is better to choose a recipient randomly than to divide the award; he gave several good reasons supporting that opinion. By contrast, I could see good arguments supporting either side of the question and, consequently, I was somewhat surprised by the strength of his conviction. This illustrates an important trait of leaders: after due consideration of the data, John sees issues as black and white, whereas most of us see them as various shades of gray. Uncertainty is always with us, but somebody has to make decisions. The contributors to this special issue wish to honor John for his many and very significant contributions to our profession, but especially for over 20 years of service as Associate Editor of I&EC Research.
Dennis C. Prieve Department of Chemical Engineering, Carnegie Mellon UniVersity Pittsburgh, PennsylVania 15213 IE900013T
