View source for New Developments in Colloid Science

Original entry:  Xu Zhang,  APPHY 225,  Fall 2009

== Reference ==
New Developments in Colloid Science D.A. Weitz and W.B. Russel, MRS Bull. Feb 2004 83 (2004)

== Keywords ==
colloids, colloidal materials, "directed" assembly, rheology, suspensions

== Summary==
  
This article summarizes several new developments of colloid science in two aspects: "directed" assembly 
of colloidal particles and understanding in rheology of colloidal suspensions.
===Directed Assembly===
====Various methods====
:1) Using depletion interaction
   
:Controllable elements: 
:1.surface treatment 
:2.solvent choice  
:3.addition of other materials

:2) Applying additional stresses ( [http://www.colloid.nl  Van Blaaderen] )
:Ex. a hard wall that restricts the states of the colloidal suspension, electric and magnetic fields, surface stresses induced by drying, oder imposed by patterned surfaces, gravitational effects,etc.

:3)Using interactions between colloidal particle
:Because thermal energy allows particles to explore phase space and achieve the lowest-energy structure, the thermalization of the particles in response to Brownian motion is essential to allowing them to self-assemble. Because the interparticle interaction energies are often far greater than <math>k_B T</math>, attractive interactions will drive the particles together to form local clusters, and these clusters can span space to form connected networks or colloidal gels.

====Main Obstacle====
:The surface energy drives the interface of the particle to be spherical, which places fundamental limitations on the structures that can be built.An important limitation comes in making [http://en.wikipedia.org/wiki/Photonic_bandgap#Computing_photonic_band_structure  photonic-bandgap structures]

====Solutions====
:1)Mix particles of different sizes and create binary alloy crystal structures
:2)Encapsulate spherical particles in emulsion droplets that are then collapsed by drying (https://sites.google.com/a/manoharan.deas.harvard.edu/www/publications   V.N. Manoharan, M.T. Elsesser, and D.J. Pine, “Dense Packing and Symmetry in Small Clusters of Microspheres”, Science 301: 483–487 (2003))
==Rheology==