Science more fantastic than fiction...
Science more fantastic than fiction: Nanoscale team launches voyage of discovery
It’s not Fantastic Voyage, the 1960s film that saw nano-scaled scientists navigate the turbulent flows of the human body. But if Rodney Fox and his Nanoscale Interdisciplinary Research Team (NIRT) achieve their goals, they’ll deliver tools engineers can use to design applications that, while fantastic, are more the stuff of science than of fiction.
Fox has received a million-dollar grant from the National Science Foundation to direct a three-year project joining scientists and engineers across several disciplines to better understand the behavior of particles in chemical reacting flows. Besides Fox, colleagues include Monica Lamm, Balaji Narasimhan, and Dennis Vigil. This ChE core is supported by Shankar Subramaniam of mechanical engineering, chemistry’s Mark Gordon, Kansas State physicist Chris Sorensen, and University of Minnesota mechanical engineer Sean Garrick.
The work of NIRT is of special interest to the chemical and pharmaceutical industries in their efforts to prevent nanoparticles from aggregating into larger units that might alter the fundamental characteristics of their products. (Raquel Welch and company spent the better part of Fantastic Voyage fighting their own potentially fatal “aggregation” with various particles in their patient’s bloodstream and other body systems.)
Controlling aggregation at the nanoscale will affect a host of applications, including systems for delivering drugs across membranes and other tissue barriers too complex to be penetrated by the microparticles used in other systems. New composite materials having both matrix and nanoscale phases would exhibit greatly improved strength-to-weight ratios, allowing for enhanced fuel efficiency in aircraft. Even commodities such as paints that have both fluid and particulate phases would enjoy improved longevity and uniformity.
“If we can understand what happens, we can control it,” says Fox. “Now this is done empirically—kind of a hit-and-miss proposition.” The research team will examine the behavior of particles at various stages of the chemical reaction process within their own areas of expertise, including quantum mechanical calculations, particle surface chemistry, molecular dynamic simulations, and large-scale clusters. “It’s a multi-scale problem,” Fox adds. “That makes it interesting—and difficult.”
Because the project moves from a sub-atomic to an atomic length scale, then to molecular and super-molecular levels, says Narasimhan, the general chemistry to chemical engineering workflow makes sense. “Mark Gordon’s quantum mechanics work will be utilized by Monica, and, with information I’ll give her from our experiments, she’ll supply her findings to Shankar in mechanical engineering,” he explains. “Shankar will work at the next length scale where, instead of looking at the particle surface itself, he’ll treat the whole particle as a ‘black box’—a coarser description of the system.
“After this come Dennis and Rodney,” Narasimhan continues, “who will take these particles in a flow stream. They’ll shear the particles and study how shear affects aggregation. That’s the project's highest level.”
But the work of individual team members isn't rigidly sequential. After Narasimhan validates their models by characterizing individual particles through atomic force microscopy, Lamm and Gordon will use computation to explore how the particles might interact and aggregate (if at all) for a variety of surface chemistries. They will then take their findings back to Narasimhan, who will return experimental data to Lamm (a “continuous feedback loop,” Lamm calls it) so she can refine her calculations.
“It’s the bridging of length scales that’s the new part of this research,” Lamm adds. “That’s why we have Balaji on board—to ground everything we do in a real system so we can validate the outputs from our computations. His experiments will provide us with insights and validation—not quantitative so much as qualitative—so we can say our predictions match what we see in the lab.”
Neither are individual investigators sequestered in their labs. “Monica, Shankar, and I have joint meetings because we’re all trying to bridge the gap between what Mark Gordon does and what Rodney does,” says Vigil. “We want a smooth handoff between Monica’s molecular dynamic simulations and the Brownian dynamic simulations Shankar and I will be doing.”
Once Lamm characterizes the particles’ behavior under stagnant conditions, Vigil and Sorensen will validate aggregation models from her and Subramaniam inside a Taylor-Couette flow reactor. Using light scattering techniques developed by Sorenson, this will let them see what’s happening to particles undergoing shear without disturbing the flow. Finally, Fox will develop functional CFD models for actual reactor flows based on his colleagues’ data.
Such collaboration between colleagues in the same field and across several disciplines is hardly unprecedented, but instead reflects the breakdown of “formerly logical” barriers that increasingly seem arbitrary and even counterproductive.
“A lot of the action is at the interface of disciplines,” Narasimhan stresses. “Individual areas themselves have already solved lots of problems. But when they contact other fields, the richness of problems at those interfaces is tremendous; it gives you a better overview that really makes an impact. That’s why collaboration is so important.”
Not only the richness, adds Lamm, but the payoffs as well. “In the long run,” she says, “we hope we can say we’ve created a paradigm for modeling systems that don’t stop with nanoparticle aggregation but can be applied to other problems where we look at molecular-scale phenomena and know how things will behave in a large reactor.”
Crossing disciplinary boundaries to get there, one might add, will be one of the most fantastic voyages of discovery imaginable.
