(216x) Assembly of Two-Directionally Percolated Particle Networks Using Orthogonal Electric and Magnetic Fields

Bharti, B., North Carolina State University
Zhu, S., North Carolina State University
Velev, O. D., North Carolina State University

External field assisted assembly of colloidal particles is the most widely used method to obtain highly ordered one- two and three dimensional structures. However, only one type of external trigger viz., electric or magnetic or light is typically implemented to organize the particles into ordered arrays. We present a novel approach towards the formation of highly cross-linked, low density, two dimensional orthogonally percolated networks of microparticles under the action of conjugated electric and magnetic fields.  A mixture of magnetic and non-magnetic spherical latex particles when subjected to orthogonal electric and magnetic fields assemble in a range of two-dimensional interconnected structures. The properties of such multidirectionally-gelled fluids are dependent on the extent of percolation in a given direction which in turn can be tuned by modulating the directionally oriented electric or magnetic field intensity. In addition, it was established that the order of application of fields governs the equilibrium morphology of 2D structure. The role of the number density of the biparticle dispersion in controlling the interconnectivity of the assembled structure was investigated and correlated to the field intensity and duration. This method for obtaining low density gelation is rapid, robust and reversible and the cross-linked structures exist as long as the external combination of electric and magnetic fields is applied. This experimental technique for the biparticle assembly offers a potential way for fabricating smart gels and biresponsive functional materials that can find electronics and biomedical applications.