|
Electrets
Electrets are materials that contain permanent charges or permanently induced dipoles. They have a permanent electric field, just as permanent magnets have a permanent magnetic field. Electrets have been used for decades in audio and video equipment, telephones and microphones, photocopiers, printers, spray painters, and other technologies that depend on charged materials. We are examining the fundamental properties of electrets as materials. We use these materials for self-assembly and to understand the fundamental processes involved with producing (and preventing) charge on materials.
Fluid Electrets
We are examining the mechanism of charging in pure protic and aprotic solvents. We systematically dope these solvents with various solutes; small changes in the concentration of these solutes affect the charging of the fluid as it flows through a capillary under an applied potential. It is easier to perform such a systematic study using fluids, rather than solids, because fluids can be doped in a readily well-controlled, quantitative manner. Understanding the mechanism of charging fluids is of fundamental importance for understanding electrochemical processes.
The motivation for this study originates from an attempt to understand the underlying mechanism for charging in a Kelvin electrostatic generator (Movie 1). In this movie, you can see the generator charge - dyed water droplets fly away from the collection (bottom) electrodes and coat the white backdrop - and discharge - the droplets fall straight into the collection electrodes.
Self-Assembly of Microspheres
We have shown that glass microspheres self-assemble on a patterned electrode under the influence of an applied electric field (Figure 2). This process occurs for ordered arrays and arbitrary patterns, over areas up to ~0.7 cm^2, with a defect rate (e.g., missing spheres, or extra spheres) of about 1%. These arrays of microspheres on the surface of the electrode can be transferred into polymeric matrices. This method employs reusable templates to guide components rapidly (less than 5 seconds) into ordered structures that cannot be made by traditional lithographic techniques.
Select Publications
1. Wiles, J. A., et al. "A Tool for Studying Contact Electrification in Systems Comprising Metals and Insulating Polymers." Analytical Chemistry 75, 4859-4867 (2003).
2. Grzybowski, B. A., et al. "Electrostatic Self-Assembly of Macroscopic Crystals using Contact Electrification." Nature Materials 2, 241-245 (2003).
|
