Anthony (Tony) DinsmoreAssociate Professor of PhysicsUniversity of Massachusetts AmherstHasbrouck 411666 North Pleasant St.Amherst, MA 01003413-545-3786E-mail: dinsmore@physics.umass.edu

STEM Science and Engineering Saturday Seminar: Colloids and Emulsions.

The research shown here was supported by the National Science Foundation through grants DMR-0907195 and CBET-0967620.

Feb 12., 2011. UMass Amherst

Eucerin skin cream in an optical microscope

Size scale: approximately 0.4 mm (400 microns) across the image. The diameter of the big blob near the center (probably a liquid droplet) is similar in size to the diameter of a hair.

Suave hand lotion in an optical microscope

Wet Latex paint in an optical microscopeThe paint color is “Sag Harbor Gray,” but the image is grayscale.

Figure 2 | Meniscus climbing by the larva of the waterlily leaf beetle.

Figure 1 | Meniscus climbing by the water treader Mesovelia.

(Movies are included with the article!)

4 80

4

8

Ln(x)

x

Shape can be described mathematically as a logarithmheight Ln(x)

Half-and-half seen in an optical microscope(Homogenized and Pasteurized)

Brownian motion/diffusion is visible here and can also be seen by light scattering.

(Charlie Chaplin demonstrates Brownian motion – something like the chaotic dance of molecules)

Naturally occurring:

Jiang et al, Chem. Mater. 11, 2132 (1999).

http://www.theimage.com/gemstone/opal/opal.html

Colloidal CrystalsColloidal Crystals

Murray & Sanders, Philos. Mag. A 42, 721 (1980).

Made in a laboratory:

Watching crystals form

The spheres attract one another when they come close. Water, salt, and surfactant (soap) are present too, but not seen in the images.

These crystals are composed of spheres that are vastly bigger than individual molecules, but the process by which they crystallize is very similar. (And it can be seen in a microscope!)

A crystal of atoms would move MUCH faster and this process would be completed in approximately 0.00000000001 seconds! (That’s 10 picoseconds.)

(John Savage and A. D.)

Experiments with the Bubble Model of a Metal Structure Sir Lawrence Bragg, W. M. Lomer, and J. F. Nye (1954)