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In chemistry, a colloid is a phase separated mixture in which one substance of microscopically dispersed insoluble particles are suspended throughout another substance. Sometimes the dispersed substance alone is called the colloid; the term colloidal suspension refers unambiguously to the overall mixture. Unlike a solution, whose solute and solvent constitute only one phase, a colloid has a dispersed phase and a continuous phase that arise by phase separation. Typically, colloids do not completely settle or take a long time to settle completely into two separated layers.
Optical tweezers are scientific instruments that use a highly focused laser beam to hold and move microscopic and sub-microscopic objects like atoms, nanoparticles and droplets, in a manner similar to tweezers. If the object is held in air or vacuum without additional support, it can be called optical levitation.
In statistical mechanics, the radial distribution function, in a system of particles, describes how density varies as a function of distance from a reference particle.
A colloidal crystal is an ordered array of colloid particles and fine grained materials analogous to a standard crystal whose repeating subunits are atoms or molecules. A natural example of this phenomenon can be found in the gem opal, where spheres of silica assume a close-packed locally periodic structure under moderate compression. Bulk properties of a colloidal crystal depend on composition, particle size, packing arrangement, and degree of regularity. Applications include photonics, materials processing, and the study of self-assembly and phase transitions.
Microrheology is a technique used to measure the rheological properties of a medium, such as microviscosity, via the measurement of the trajectory of a flow tracer. It is a new way of doing rheology, traditionally done using a rheometer. There are two types of microrheology: passive microrheology and active microrheology. Passive microrheology uses inherent thermal energy to move the tracers, whereas active microrheology uses externally applied forces, such as from a magnetic field or an optical tweezer, to do so. Microrheology can be further differentiated into 1- and 2-particle methods.
Diffusing-wave spectroscopy (DWS) is an optical technique derived from dynamic light scattering (DLS) that studies the dynamics of scattered light in the limit of strong multiple scattering. It has been widely used in the past to study colloidal suspensions, emulsions, foams, gels, biological media and other forms of soft matter. If carefully calibrated, DWS allows the quantitative measurement of microscopic motion in a soft material, from which the rheological properties of the complex medium can be extracted via the microrheology approach.
Active matter is composed of large numbers of active "agents", each of which consumes energy in order to move or to exert mechanical forces. Such systems are intrinsically out of thermal equilibrium. Unlike thermal systems relaxing towards equilibrium and systems with boundary conditions imposing steady currents, active matter systems break time reversal symmetry because energy is being continually dissipated by the individual constituents. Most examples of active matter are biological in origin and span all the scales of the living, from bacteria and self-organising bio-polymers such as microtubules and actin, to schools of fish and flocks of birds. However, a great deal of current experimental work is devoted to synthetic systems such as artificial self-propelled particles. Active matter is a relatively new material classification in soft matter: the most extensively studied model, the Vicsek model, dates from 1995.
Eric R. Weeks is an American physicist. He completed his B.Sc. at the University of Illinois at Urbana–Champaign in 1992. He obtained a Ph.D. in physics from the University of Texas at Austin in 1997, working under Harry Swinney, and later completed post-doctoral research with David Weitz and Arjun Yodh at Harvard University and the University of Pennsylvania. He is currently a full professor at Emory University in Atlanta, Georgia.
Michael Elmhirst Cates is a British physicist. He is the 19th Lucasian Professor of Mathematics at the University of Cambridge and has held this position since 1 July 2015. He was previously Professor of Natural Philosophy at the University of Edinburgh, and has held a Royal Society Research Professorship since 2007.
Differential dynamic microscopy (DDM) is an optical technique that allows performing light scattering experiments by means of a simple optical microscope. DDM is suitable for typical soft materials such as for instance liquids or gels made of colloids, polymers and liquid crystals but also for biological materials like bacteria and cells.
Sharon C. Glotzer is an American scientist and "digital alchemist," the Anthony C. Lembke Department Chair of Chemical Engineering, the John Werner Cahn Distinguished University Professor of Engineering and the Stuart W. Churchill Collegiate Professor of Chemical Engineering at the University of Michigan, where she is also Professor of Materials Science & Engineering, Professor of Physics, Professor of Macromolecular Science & Engineering, and Professor of Applied Physics. She is recognized for her contributions to the fields of soft matter and computational science, most notably on problems in assembly science and engineering, nanoscience, and the glass transition, for which the elucidation of the nature of dynamical heterogeneity in glassy liquids is of particular significance. She is a member of the National Academy of Sciences, the National Academy of Engineering, and the American Academy of Arts and Sciences.
A depletion force is an effective attractive force that arises between large colloidal particles that are suspended in a dilute solution of depletants, which are smaller solutes that are preferentially excluded from the vicinity of the large particles. One of the earliest reports of depletion forces that lead to particle coagulation is that of Bondy, who observed the separation or 'creaming' of rubber latex upon addition of polymer depletant molecules to solution. More generally, depletants can include polymers, micelles, osmolytes, ink, mud, or paint dispersed in a continuous phase.
David G. Grier is an American physicist whose research focuses on experimental soft condensed matter physics—an interdisciplinary field that includes physics, chemistry, biology, and nanotechnology, aiming to understand how objects interacting in simple ways manage to organize into sophisticated hierarchies of structure and function.
David J. Pine is an American physicist who has made contributions in the field of soft matter physics, including studies on colloids, polymers, surfactant systems, and granular materials. He is Professor of Physics in the NYU College of Arts and Science and Chair of the Department of Chemical and Biomolecular Engineering at the NYU Tandon School of Engineering.
Many experimental realizations of self-propelled particles exhibit a strong tendency to aggregate and form clusters, whose dynamics are much richer than those of passive colloids. These aggregates of particles form for a variety of reasons, from chemical gradients to magnetic and ultrasonic fields. Self-propelled enzyme motors and synthetic nanomotors also exhibit clustering effects in the form of chemotaxis. Chemotaxis is a form of collective motion of biological or non-biological particles toward a fuel source or away from a threat, as observed experimentally in enzyme diffusion and also synthetic chemotaxis or phototaxis. In addition to irreversible schooling, self-propelled particles also display reversible collective motion, such as predator–prey behavior and oscillatory clustering and dispersion.
Elihu Abrahams was a theoretical physicist, specializing in condensed matter physics. He is mostly notable for his work on electron transport in disordered systems.
Sriram Rajagopal Ramaswamy FRS is a Professor at the Indian Institute of Science, Bangalore and was on leave (2012–16) as Director of the Tata Institute of Fundamental Research (TIFR) Centre for Interdisciplinary Sciences in Hyderabad.
Maria Cristina Marchetti is an Italian-born, American theoretical physicist specializing in statistical physics and condensed matter physics. In 2019, she received the Leo P. Kadanoff Prize of the American Physical Society. She held the William R. Kenan, Jr. Distinguished Professorship of Physics at Syracuse University, where she was the director of the Soft and Living Matter program, and chaired the department 2007-2010. She is currently Professor of Physics at the University of California, Santa Barbara.
Sharon J. Gerbode is a soft matter physicist and the Iris and Howard Critchell Associate Professor of Physics at Harvey Mudd College. She is recognized for her contributions to the fields of soft matter and biomechanics and is a 2016 Cottrell Scholar, a distinction given to top early career academic scientists by the Research Corporation for Science Advancement (RCSA).
Douglas J. Durian is Professor of Physics and Astronomy at the University of Pennsylvania. He is known for his research contributions to the field of experimental soft matter, particularly in the areas of foams and granular flows. He has held multiple visiting professorships and leaderships positions in the soft matter physics community. He is a Fellow of the American Physical Society.
References
- 1 2 "John C. Crocker".
- ↑ "John C Crocker". scholar.google.com.
- ↑ "John Charles Crocker" (PDF).
- ↑ "Particle tracking using IDL". www.physics.emory.edu.
- ↑ "Matlab Particle Tracking". site.physics.georgetown.edu.
- ↑ "Trackpy: Fast, Flexible Particle-Tracking Toolkit — trackpy 0.4.2 documentation". soft-matter.github.io.
- ↑ Rogers, W. Benjamin; Crocker, John C. (April 1, 2014). "A tunable line optical tweezers instrument with nanometer spatial resolution". Review of Scientific Instruments. 85 (4): 043704. doi:10.1063/1.4870806. PMID 24784615 – via aip.scitation.org (Atypon).
- ↑ Crocker, John C.; Valentine, M. T.; Weeks, Eric R.; Gisler, T.; Kaplan, P. D.; Yodh, A. G.; Weitz, D. A. (July 24, 2000). "Two-Point Microrheology of Inhomogeneous Soft Materials". Physical Review Letters. 85 (4): 888–891. doi:10.1103/PhysRevLett.85.888. PMID 10991424 – via APS.
- ↑ Biancaniello, Paul L.; Kim, Anthony J.; Crocker, John C. (February 10, 2005). "Colloidal Interactions and Self-Assembly Using DNA Hybridization". Physical Review Letters. 94 (5): 058302. doi:10.1103/PhysRevLett.94.058302. PMID 15783705 – via APS.
- ↑ Hwang, Hyun Joo; Riggleman, Robert A.; Crocker, John C. (September 17, 2016). "Understanding soft glassy materials using an energy landscape approach". Nature Materials. 15 (9): 1031–1036. doi:10.1038/nmat4663. PMID 27322823 – via www.nature.com.
- ↑ "Crocker, John C."
- ↑ "PopSci's Fourth Annual Brilliant 10". Popular Science.
- ↑ "APS Fellow Archive". www.aps.org.