Michael J. Solomon

Our research falls broadly into two categories: (i) nanocolloid assembly and microdynamics; (ii) polymer fluid dynamics. In both areas we develop new experiments, instrumentation and analytical tools to link technological development to fundamental principles. Descriptions of our current research areas are below. Please the group’s web page for more information about current projects.

Nanocolloidal assembly
The assembly of nanocolloids into useful structures and morphologies has long been a key aim of chemical engineers and materials scientists. For example, ordered arrays of colloidal particles formed in the liquid state by application of electric and shear fields can be further processed to yield structures useful for sensing and optical materials. Yet, the success of this technological aim is severely hindered by some deep fundamental problems. First, ordered assemblies are often compromised by defect structures, such as vacancies, stacking faults and grain boundaries. Second, the range of assemblies that have been fabricated on large scales to date is disappointingly small, perhaps because typical nanocolloidal buildling blocks are not nearly complex as molecules. Third, non-idealities peculiar to the nanoscale, such as gelation and jamming, complete with the assembly of ordered structures.

We address these scientific and technological issues with a program that includes novel colloid synthesis, direct visualization of assembly structure and dynamics by confocal microscopy as well as rheological measurements. For example, we have synthesized micron-scale polymer fluorescent rods and discovered nematic ordering upon sedimentation. We have used shear flow to grow close-packed nanocolloidal crystals whose stacking fault structure can be characterized by confocal microscopy. We have resolved new kinds of heterogeneity and pore structures in colloidal particle gels. This work is of broad interest to the development of new materials and processes based on nanotechnology as well as the engineering of inks, paints and ceramics.

Polymer fluid dynamics
We seek to understand the relationship between flow strength and the stability and structure of macromolecules such as synthetic polymers and DNA. Our principal interest to date has been in the limitations that polymer chain scission places on polymer turbulent drag reduction, a technology of interest to pipeline as well as fast ocean transport. In collaboration with mechanical engineering colleagues we have investigated how scission, degradation and aggregation of drag reducing polymer such as poly(ethylene oxide) impact their drag reducing capability. In this project we have applied microfluidic technology to develop model flows to characterize the effect of shear and extension on polymer properties.

Our current research is supported by NSF and DARPA.

Research Interests