Thomas G. Mason

University of California- Los Angeles

Physicist / Chemist

Fellow, Elected 2021

Mason created, demonstrated, and developed the approach of thermal-entropic 'passive' microrheology. Using both optical scattering methods as well as real-space microscopic particle tracking techniques applied to a variety of soft materials, Mason established the link between linear viscoelastic shear moduli and average time-dependent motion of probes through the generalized Stokes-Einstein relation. Mason also developed experimental methods of two-probe particle tracking microrheology, implemented the first high-speed real-space microscopic imaging of probe motion in microrheology, and he extended passive microrheology to include rotational motion of non-spherical probes. His passive microrheology approach and methods are now used in several commercial optical instruments. Beyond passive microrheology, Mason's experiments on the linear and non-linear rheology of disordered monodisperse emulsions established a clear link between droplet crowding and the onset of plateau shear elasticity. This provided an important prototype example of random jamming of uniform, deformable colloidal objects in soft matter systems prior to the introduction of jamming terminology. Mason's investigations of emulsification and droplet restructuring in viscoelastic media, including real-time light scattering monitoring during large-amplitude oscillatory shear in concentrated emulsions, have revealed important composition-structure-flow history relationships. Mason's foundational experiments on extreme emulsification have led to methods for making elastic nanoemulsions, including multi-compartment nanodroplets, and for controlling their size distributions, rheological properties, and optical properties.

Mason holds a joint appointment as professor of chemistry and professor of physics at UCLA. Mason received dual B.S. degrees in physics and electrical engineering from University of Maryland-College Park and a Ph.D. in physics from Princeton University. He is a fellow of the American Physical Society and of the American Association for the Advancement of Science. Mason has received numerous awards, including NSF's Career Award, UCLA's McTague Chair, and Rheologica Acta's publication award. He has published over 130 research articles, and he is the primary inventor of over 15 patents.