New Developments in Colloid Science
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New Developments in Colloid Science
D.A. Weitz and W.B. Russel, Guest Editors Abstract This introductory article reviews the topics covered in this issue of MRS Bulletin on New Developments in Colloid Science. Colloidal particles have a long history of importance in a broad range of applications in technology and materials processing. They can be made from many different materials and suspended in a wide variety of solvents. The rheological properties of colloidal suspensions have traditionally been of primary concern in their technological applications, and our understanding of these properties continues to evolve. However, new uses of colloidal particles are also emerging. Because they can be produced to a precise size, colloidal particles are now also being used in novel ways as building blocks for engineering completely new materials, including high-precision filters, controlled-porosity substrates, and photonic devices. In addition, new methods are evolving to alter the shape of the particles and create controlled structures with nonspherical particles. New experimental techniques are allowing improved measurement and increased understanding of the structure, properties, and behavior of colloidal suspensions. Significant progress continues to be made, and the potential uses of colloidal particles continue to grow. This issue presents a snapshot summary of recent developments in this field. Keywords: colloids, colloidal materials, rheology, suspensions.
Colloids are small solid particles dispersed in a medium, typically a fluid. Colloidal particles have a long history of importance in a broad range of applications in technology and materials processing, extending from the pigments used in ancient inks to the photonic-bandgap materials being developed today. Particles can be made from many different materials and suspended in a wide variety of solvents. The typical size of colloidal particles ranges from nanometers to micrometers. Because of this small size, thermal energy induces Brownian motion of the particles, and the resultant dynamics can play an important role in the properties of the suspension. The typical volume fraction of solids in a colloidal suspension can vary from a small fraction of a percent to more than 60%. The consequences on the suspension behavior as the volume fraction increases are still not completely understood, yet they are of great fundamental interest and practical importance. Colloidal suspensions have considerable technological importance. They represent a means of making solid or highly viscous materials flow like low-viscosity fluids; this is because the solid or high-viscosity
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material is contained in the colloidal particles while the rheological properties are dominated by the continuous-phase fluid in which the particles are dispersed, which can have a relatively low viscosity. Colloidal suspensions are also of great scientific interest, motivated not only by their technological applications but also by their potential use as models to investigate the collective phase
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