Why and how do colloidal gels form? What is the relationship between gels and glasses, states that occur when particles crowd each other to the point of dynamic arrest? There is long-running debate regarding the mechanism of colloidal gelation, particularly at moderate to high particle volume fractions and relatively weak attractive interactions. The aim of this work is to investigate the microrheology of colloidal glasses and gels to determine whether there is a direct relation between these states. The work is accomplished through the development of optical trapping experiments and Stokesian dynamics simulations that measure the response of individual probe particles in colloidal suspensions. Since theories of colloidal glasses and gels are microrheological, but few studies to date have examined and attempted to validate these theories on microscopic length scales, such work is timely.
Colloidal gels are an arrested, non-equilibrium state of matter that impact shelf life of consumer care products, agrochemicals, coatings, pigments and inks?potentially any product or material in which particles are suspended at high concentration in a fluid phase. Moreover, glasses and gels are ubiquitous states of matter in molecular, macromolecular and colloidal materials. The insights gained under this project have broad implications for our fundamental understanding of many materials. Through an integrated education and professional training of graduate students from underrepresented backgrounds in STEM disciplines and outreach activities involving undergraduate research experiences and research experiences for teachers, this work enhances the capacity for US innovation in the chemical and advanced materials industries.
