Predicting the disorderorder transition of dielectrophoretic colloidal assembly with dielectric spectroscopy

The dielectrophoretic assembly of colloidal suspensions into crystalline arrays is described by a master scaling that collapses the disorderorder 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 m by light scattering (Lumsdon et al., Langmuir 2004, 20, 21082116; McMullan and Wagner, Langmuir 2012, 28, 41234130), optical laser tweezer measurements (Mittal et al., J. Chem. Phys. 2008, 129, 064513), and small-angle neutron scattering (McMullan and Wagner, Soft Matter 2010, 6, 54435450). In this work, we reconcile the empirical phase diagram with direct measurements of the colloid polarizability using dielectric spectroscopy. Dielectric spectroscopy confirms the origin of the orderdisorder transition frequency dependence, including its quadratic scaling with particle radius, a2, and provides an alternative method to search for optimal self-assembly conditions.