Tunable Electric Field Processing of Composite Materials

Using the dielectrophoretic effect, it is possible to fabricate polymer/ceramic composite materials in which the filler phase can be manipulated to form a desired microstructure. This is performed via the application of an electric field to a colloidal suspension consisting of a filler material dispersed in a fluid polymer medium. Field induced dipole-dipole interactions cause particles to experience a mutual interaction resulting in distinct particle chains which align parallel to the applied electric field direction. This chained microstructure can then be "frozen in" by crosslinking the polymer matrix. The chaining phenomena is dependent on both the magnitude and the frequency of the applied field. Optimum assembly conditions for this process are determined via optical microscopy and electrorheological measurements. The dielectrophoretic assembly process also has the advantage of in-situ quality control through dielectric measurements. Both the degree of alignment and the batch uniformity can be confirmed via dielectric measurements. By varying the applied field and frequency, chain coarseness can be manipulated giving rise to the ability to "tune" the properties of the composite. The dielectrophoretic assembly process is projected to be utilized for electrical, structural and thermal composite applications.