scispace - formally typeset
Search or ask a question
Author

Thomas G. Mason

Bio: Thomas G. Mason is an academic researcher from University of California, Los Angeles. The author has contributed to research in topics: Microrheology & Diffusing-wave spectroscopy. The author has an hindex of 50, co-authored 171 publications receiving 12507 citations. Previous affiliations of Thomas G. Mason include Princeton University & University of California, Berkeley.


Papers
More filters
Journal ArticleDOI
TL;DR: A novel method for measuring the linear viscoelastic properties of a complex fluid over an extended range of frequencies is presented, showing that the response of the fluid to thermal fluctuations, as probed by the average motion of small particles dispersed within the fluid, provides a close representation of theresponse of the bulk fluid to an imposed shear strain.
Abstract: In this Letter, we present a novel method for measuring the linear viscoelastic properties of a complex fluid over an extended range of frequencies. We show that the response of the fluid to thermal fluctuations, as probed by the average motion of small particles dispersed within the fluid, provides a close representation of the response of the bulk fluid to an imposed shear strain. The essential physics of this approach is that the bulk mechanical susceptibility of the fluid determines the response of a small particle excited by the thermal stochastic forces which lead to Brownian motion. We use dynamic light scattering to measure the mean square displacement of a probe particle, kDr 2 stdl, and relate this to G p svd by describing the motion of the particle with a generalized Langevin equation, incorporating a memory function to account for the viscoelasticity. We compare this G p svd to that measured by conventional mechanical means. Remarkably good agreement is found. We demonstrate the flexibility of this new technique by measuring the moduli of a variety of complex fluids, and illustrate its potential to determine new behavior. We describe the motion of a small, neutrally buoyant particle dispersed in a complex fluid by means of generalized Langevin equation [2,3],

1,407 citations

Journal ArticleDOI
TL;DR: In this article, the authors summarize procedures for producing nanoemulsions comprised of nanoscale droplets, methods for controlling the droplet size distribution and composition, and interesting physical properties of nanoEMulsions.
Abstract: We summarize procedures for producing 'nanoemulsions' comprised of nanoscale droplets, methods for controlling the droplet size distribution and composition, and interesting physical properties of nanoemulsions. In contrast to more common microscale emulsions, nanoemulsions exhibit optical transparency at high droplet volume fractions, , surprisingly strong elasticity at low , and enhanced diffusive transport and shelf stability. For these reasons, nanoemulsions have great potential in a wide range of industries including pharmaceuticals, foods, and personal care products.

897 citations

Journal ArticleDOI
TL;DR: In this article, the authors used photodiode detection of laser light scattered from a thermally excited colloidal probe sphere to track its trajectory and extract the moduli using a frequency-dependent Stokes-Einstein equation.
Abstract: We present a new method for measuring the linear viscoelastic shear moduli of complex fluids. Using photodiode detection of laser light scattered from a thermally excited colloidal probe sphere, we track its trajectory and extract the moduli using a frequency-dependent Stokes-Einstein equation. Spectra obtained for polyethylene oxide in water are in excellent agreement with those found mechanically and using diffusing wave spectroscopy. Since only minute sample volumes are required, this method is well suited for biomaterials of high purity, as we demonstrate with a concentrated DNA solution.

751 citations

Journal ArticleDOI
Thomas G. Mason1
TL;DR: In this paper, the linear viscoelastic shear moduli of complex fluids were obtained from the time-dependent mean square displacement,, of thermally-driven colloidal spheres suspended in the fluid using a generalized Stokes-Einstein (GSE) equation.
Abstract: We obtain the linear viscoelastic shear moduli of complex fluids from the time-dependent mean square displacement, , of thermally-driven colloidal spheres suspended in the fluid using a generalized Stokes–Einstein (GSE) equation. Different representations of the GSE equation can be used to obtain the viscoelastic spectrum, G˜(s), in the Laplace frequency domain, the complex shear modulus, G*(ω), in the Fourier frequency domain, and the stress relaxation modulus, Gr(t), in the time domain. Because trapezoid integration (s domain) or the Fast Fourier Transform (ω domain) of known only over a finite temporal interval can lead to errors which result in unphysical behavior of the moduli near the frequency extremes, we estimate the transforms algebraically by describing as a local power law. If the logarithmic slope of can be accurately determined, these estimates generally perform well at the frequency extremes.

634 citations

Journal ArticleDOI
TL;DR: In this article, the authors summarize procedures for producing nanoemulsions comprised of nanoscale droplets, methods for controlling the droplet size distribution and composition, and interesting physical properties of nanoEMulsions.
Abstract: We summarize procedures for producing 'nanoemulsions' comprised of nanoscale droplets, methods for controlling the droplet size distribution and composition, and interesting physical properties of nanoemulsions. In contrast to more common microscale emulsions, nanoemulsions exhibit optical transparency at high droplet volume fractions, , surprisingly strong elasticity at low , and enhanced diffusive transport and shelf stability. For these reasons, nanoemulsions have great potential in a wide range of industries including pharmaceuticals, foods, and personal care products.

604 citations


Cited by
More filters
Journal ArticleDOI
TL;DR: This work argues for a conceptual framework for these new building blocks based on anisotropy attributes and discusses the prognosis for future progress in exploiting an isotropy for materials design and assembly.
Abstract: A revolution in novel nanoparticles and colloidal building blocks has been enabled by recent breakthroughs in particle synthesis These new particles are poised to become the ‘atoms’ and ‘molecules’ of tomorrow’s materials if they can be successfully assembled into useful structures Here, we discuss the recent progress made in the synthesis of nanocrystals and colloidal particles and draw analogies between these new particulate building blocks and better-studied molecules and supramolecular objects We argue for a conceptual framework for these new building blocks based on anisotropy attributes and discuss the prognosis for future progress in exploiting anisotropy for materials design and assembly

2,558 citations

Journal ArticleDOI
TL;DR: In this paper, a flow-focusing geometry is integrated into a microfluidic device and used to study drop formation in liquid-liquid systems, where both monodisperse and polydisperse emulsions can be produced.
Abstract: A flow-focusing geometry is integrated into a microfluidic device and used to study drop formation in liquid–liquid systems. A phase diagram illustrating the drop size as a function of flow rates and flow rate ratios of the two liquids includes one regime where drop size is comparable to orifice width and a second regime where drop size is dictated by the diameter of a thin “focused” thread, so drops much smaller than the orifice are formed. Both monodisperse and polydisperse emulsions can be produced.

2,264 citations

01 Jan 2016

1,715 citations

Journal ArticleDOI
TL;DR: The molecular and physical information coded within the extracellular milieu is informing the development of a new generation of biomaterials for tissue engineering, and exciting developments are likely to help reconcile the clinical and commercial pressures on tissue engineering.
Abstract: The molecular and physical information coded within the extracellular milieu is informing the development of a new generation of biomaterials for tissue engineering. Several powerful extracellular influences have already found their way into cell-instructive scaffolds, while others remain largely unexplored. Yet for commercial success tissue engineering products must be not only efficacious but also cost-effective, introducing a potential dichotomy between the need for sophistication and ease of production. This is spurring interest in recreating extracellular influences in simplified forms, from the reduction of biopolymers into short functional domains, to the use of basic chemistries to manipulate cell fate. In the future these exciting developments are likely to help reconcile the clinical and commercial pressures on tissue engineering.

1,555 citations

Journal ArticleDOI
TL;DR: This review discusses efforts to create next-generation materials via bottom-up organization of nanocrystals with preprogrammed functionality and self-assembly instructions, and explores the unique possibilities offered by leveraging nontraditional surface chemistries and assembly environments to control superlattice structure and produce nonbulk assemblies.
Abstract: Chemical methods developed over the past two decades enable preparation of colloidal nanocrystals with uniform size and shape. These Brownian objects readily order into superlattices. Recently, the range of accessible inorganic cores and tunable surface chemistries dramatically increased, expanding the set of nanocrystal arrangements experimentally attainable. In this review, we discuss efforts to create next-generation materials via bottom-up organization of nanocrystals with preprogrammed functionality and self-assembly instructions. This process is often driven by both interparticle interactions and the influence of the assembly environment. The introduction provides the reader with a practical overview of nanocrystal synthesis, self-assembly, and superlattice characterization. We then summarize the theory of nanocrystal interactions and examine fundamental principles governing nanocrystal self-assembly from hard and soft particle perspectives borrowed from the comparatively established fields of micro...

1,376 citations