PI: Niels Holten-Andersen and Bradley Olsen
Holten-Andersen and Olsen have developed a new tool that enables simultaneous measurement of rheology and fluorescence signal in polymer molecules and used this to quantify the number of dissociated bonds in a hydrogel under shear flow with a metal coordinate polymer system where bond fluorescence is quenched in the bound state and activated in the unbound state. These measurements are the first measurements of dissociated bonds in hydrogels under flow, and they provide a valuable point of comparison with theoretical studies. The impact of the work is to show that theories based on chain retraction as the primary relaxation mechanism are unable to capture the number of dissociated bonds and viscosity with the same set of fit parameters, while theories that allow for other relaxation mechanisms can more accurately reproduce the experimental data.
Graphs showing experiment (left) and modeling (right) for the fraction of dissociated bonds (top) and normalized viscosity (bottom). Graphs on the right compare data to three different theoretical predictions.
During spring 2019, Olsen was a visiting professor at the State University of Campinas (UNICAMP) in Brazil. During this time, he taught the class IQ401 (Chemical Engineering Thermodynamcis) jointly with Prof. Marisa Beppu of the School of Chemical Engineering at UNICAMP. During this class, Olsen is helping to transition many of the teaching methods developed at MIT, including the use of active learning, video lectures, and more modern example problems, into the classroom of one of the leading universities in Brazil. This experience is also helping to develop an appreciation for the regional differences among students, both intellectually and culturally, and how to develop teaching methods that are regionally effective.
Olsen teaching thermodynamics at UNICAMP