Research Highlight: Forces in Electrorheological (ER) Fluids An ER fluid is a material whose viscosity (resistance to flow) can be changed by an electric field (e. g. with a battery). They usually consist of suspensions of dielectric spheres in a host made of another insulator. If an electric field is applied, the spheres line up, making the suspension more viscous (instead of behaving like water, it becomes more like honey). In our method, we connect the forces to the optical properties of the spheres. Theory of Superconducting and Electromagnetic Properties of Some Nanostructured MaterialsDavid Stroud, Ohio State UniversityNSF DMR04-13395 E SrTi03 Silicone oil Two strontium titanate spheres (diameter 6.3 mm) in silicone oil are strongly attracted when electric field E = 71 volts/mm is applied. Force is strongly attractive and depends on frequency. Spheres separated by only 0.1-0.3mm
Contributions to Education: Six grad students (Kwangmoo Kim, Daniel Valdez-Balderas, Ivan Tornes, Kohjiro Kobayashi, Vishwesha Guttal, Rakesh Tiwari), one postdoc (Sung Yong Park), one undergrad REU student (Bryan Chen) and another undergrad (Stefan Natu) have contributed to work on this grant. Ivan Tornes is now a staff scientist at Battelle; Park has a postdoc at Northwestern. I have discussed ER fluids in my graduate electromagnetism course, including research findings from this work. Theory of Superconducting and Electromagnetic Properties of Some Nanostructured MaterialsDavid Stroud, Ohio State UniversityNSF DMR04-13395 • Some potential applications: • Change in viscosity with applied electric field gives a motoroilwithcontrollablethickness (already used in car brakes). • 2. At optical frequencies, if the spheres are small and metallic, rather than large and non-metallic, the same principle can be used to calculate the force between the spheres induced by a strong light beam. • Publications: • Kwangmoo Kim, David Stroud, • X. Li, D. J. Bergman, Phys. Rev. • E71, 031503 (2005); Li, Bergman and Stroud, Europhys. Lett. 69, 1010 (2005).