Chicago Materials Research Center (MRSEC)

Skip to: main navigation | main content

Research Nuggets

Educational Outreach

Demo Team

The Demo Team presents cutting-edge research and contemporary science to the general public. We put together small interactive science demonstrations and present them at local science museums & schools.

The majority of our demonstrations have been presented at The Museum of Science and Industry on weekend afternoons. We engage museum visitors of all ages and all types of science backgrounds with hands-on demonstrations of current topics in science--from very young children to seasoned professionals.

In addition to regularly presenting demonstrations at local science museums we are also designing and building prototypes for exhibits which can be used as unmanned stations in science museums. Currently we are working on three such prototypes dealing with forcechains in granular materials, liquid drops, and coffee stains.

January/February 2005

Our Team

The demo team consists of MRSEC graduate students and post-docs in physics and chemistry, but we encourage anyone interested in bringing current science to the public to join. Send questions to Dr. Ward Lopes at walopes@uchicago.edu.

Below is a list of some activities of the MRSEC demo team in 2004/2005:

Back to Top

Granular Materials

Here we present demos about research on a class of materials that sometimes behave like solids, sometimes like liquids, sometimes like dense gases, and often like all of these at once. These granular materials are large assemblages of individual solids ("grains") and include such familiar items as coffee beans or grounds, gravel, powders, pharmaceutical pills, fertilizer, grain, seeds, ....., or sand. They are materials that are all around us and which are of tremendous importance for many industrial processes. Yet even though granular materials appear simple, they display an astounding range of complex behavior that has largely been unexplored.

Image: Forcechains in granular materials. Cutting-edge research sometimes results from simple experiments. The same Brazil nut effect that we demonstrate is also being studied at UofC. Prof. Jeager's group. This is the abstract from a paper (Nature 414, 270 (15 November 2001); doi:10.1038/35104697) : Granular media differ from other materials in their response to stirring or jostling — unlike two-fluid systems, bi-disperse granular mixtures will separate according to particle size when shaken, with large particles rising, a phenomenon termed the 'Brazil-nut effect'. Mounting evidence indicates that differences in particle density affect size separation in mixtures of granular particles. We show here that this density dependence does not follow a steady trend but is non-monotonic and sensitive to background air pressure. Our results indicate that particle density and interstitial air must both be considered in size segregation.

Back to Top

Fluids

Rheoscopic fluids are extremely effective in producing visual images of dynamic currents. Research laboratories and teaching institutions throughout the world use them for the study and demonstration of fluid flow. The fluids are suspensions of microscopic crystalline platelets. When they are put into motion, the suspended platelets orient so as to align their larger dimensions parallel to the planes of shear. In the presence of incident light, areas of varying orientation will reflect differing intensities of light, and their evolution and movement will produce striking visual images of the currents taking place.

Image: Rheoscopic Fluid. Prof Nagel at UofC studies the singularities in free-surface flows. A drop falling from a faucet is a common example of a liquid fissioning into two or more pieces. The cascade of structure that is produced in this process is of uncommon beauty. As the drop falls, a long neck, connecting two masses of fluid, stretches out and then breaks. What is the shape of the drop at the instant of breaking apart?

Back to Top

New Materials

The Chicago Materials Research Center addresses fundamental scientific problems of technological significance. MRSEC develops, describes and improves materials. The purpose of this demo is to show new materials and their possible applications in every day life.

Image: Ferrofluids - Liquid magnets. Ferrofluids are an amazing spin-off of the US Space Program. They were invented by NASA as a way to control the flow of liquid fuels in space. A ferrofluid is a special solution of magnetic particles in a colloidal suspension whose flow can be controlled by magnets or magnetic fields. Ferrofluids have 3 unique properties:

Back to Top

Total Internal Reflection

Image: Fiber optics.

When light is incident upon a medium of lesser index of refraction, the ray is bent away from the normal, so the exit angle is greater than the incident angle. Such reflection is commonly called "internal reflection". The exit angle will then approach 90° for some critical incident angle , and for incident angles greater than the critical angle there will be total internal reflection.

Back to Top

Fluorescence

Fluorescence is a member of the ubiquitous luminescence family of processes in which susceptible molecules emit light from electronically excited states created by either a physical (for example, absorption of light), mechanical (friction), or chemical mechanism. Generation of luminescence through excitation of a molecule by ultraviolet or visible light photons is a phenomenon termed photoluminescence, which is formally divided into two categories, fluorescence and phosphorescence, depending upon the electronic configuration of the excited state and the emission pathway. Fluorescence is the property of some atoms and molecules to absorb light at a particular wavelength and to subsequently emit light of longer wavelength after a brief interval, termed the fluorescence lifetime. The process of phosphorescence occurs in a manner similar to fluorescence, but with a much longer excited state lifetime.

Image: Chemical Fluorescence - Glow sticks. A multicolor labeling experiment entails the deliberate introduction of two or more probes to simultaneously monitor different biochemical functions. This technique has major applications in flow cytometry, DNA sequencing, fluorescence in situ hybridization and fluorescence microscopy. Example of research that uses fluorescence properties: Prof. Ka Yee Lee at the University of Chicago utilizes fluorescence microscopy as a probe to study lipid-protein interactions.

Back to Top

Image: Plasma Ball.

Forces

We decided to demonstrate the properties of forces.

Our demos of the nature of forces include:

Back to Top