(358g) Predicting the Disorder-Order Transition of Dielectrophoretic Colloidal Assembly With Dielectric Spectroscopy

The self-assembly of colloidal building blocks into ordered, periodic structures using directing electric fields is a rapid, highly scalable, and potentially low-cost route for manufacturing functional nanomaterials and devices. The dielectrophoretic assembly of colloidal suspensions into crystalline arrays follows a master scaling that collapses the disorder-order transition as a function of field strength, frequency and particle size.  This master scaling has been verified for particle diameters ranging from 2a = 200 nm to 3 mm by light scattering (Lumsdon et al., Langmuir 20, 2108-2116, 2004; McMullan and Wagner, Langmuir 28, 4123-4130, 2012), laser tweezer pair interaction measurements (Mittal et al., J. Chem. Phys. 129, 064513, 2008) and small-angle neutron scattering (McMullan and Wagner, Soft Matter 6, 5443-5450, 2010).   In this work, we reconcile the established empirical phase diagram with direct measurements of the colloid polarizability using dielectric spectroscopy.  By varying volume fraction, particle size and ionic strength, we confirm the disorder-to-crystal electric field assembly phase diagram.  This represents an alternative means to search for optimal self-assembly conditions that is not limited by particle size, shape, chemistry or solvent characteristics.