Hello dear. by rheological analysis you can study interactions making analysis under oscillatory conditions (dynamic). you can obtain plots of complex viscosity vs angular frequency, stress vs strain, creep analysis, elastic and viscous modulus. You can make inferences from these analysis regard to interactions.
Lots of links to apps notes on the page. For example: http://www.malvern.com/en/support/resource-center/application-notes/AN120907DetectingProteinAggregation.aspx
The Zetasizer is extremely well used and very popular system in the nanotechnology arena. Let me know if any questions.