(394j) Dielectrophoretic Response of Polystyrene Particles and Perfluorocarbon Oil-Core, Chitosan/Poly-L-Lysine/CaPO4 Shell Nanoparticles

Chungja Yang¹, Chun-Jen Wu², Agnes E. Ostafin², and Adrienne Minerick¹

¹Chemical Engineering Department, MTU

²Materials Science and Engineering Department, University of Utah

Dynamic (dis)assembly of nanoparticles into three-dimensional, packed structures would be useful for drug delivery, nanoparticle films and diagnostics.  Dielectrophoretic (DEP) microdevices can rapidly assemble, discriminate, and manipulate particles based on a polarizability and medium interactions within non-uniform electric fields. DEP has been used to discern micrometer scale cells and particles, but the manipulation of nanometer scale objects such as viruses, proteins, and nanoparticles has seen less exploration due to the lower forces on these smaller particles. In this work, we examine dielectrophoretic behaviors of spherical core-shell nanoparticles (CSnp) in 2D and 3D particle-assemblies in order to determine dielectric properties (permittivity and conductivity) of the core and shell. Three types of CSnp were custom synthesized with a perfluorocarbon oil liquid core within a phospholipid micelle templating for three shell materials (chitosan, poly-L-lysine, and CaPO₄).  The synthesis procedures for all three biocompatible shell materials are established and demonstrate a range of permittivities (chitosan= 7.1*10^-10-4.4*10^-9 F/m, poly-L-lysine= 6.2*10^-10-8.0*10^-10 F/m, CaPO₄= Unknown) and conductivities (chitosan= 3.0*10^-4- 3.5*10^-1 S/m, poly-L-lysine, CaPO₄= Unknown) based on concentrations and frequencies. We report the frequency-dependent and medium conductivity-dependent responses of ~250 nm CSnps with ~10 nm shells for all three shell types. Experiments were conducted within a 100 nl chamber housing 100 um wide Ti/Au quadrupole electrodes spaced 25 um apart. Frequencies from 100kHz to 80MHz at a fixed local field of 10V_pp were tested and the frequency-dependent DEP responses of the nanoparticles were quantified by tracking optical intensity profiles via video microscopy.  Average velocity of particles inferred from intensity profiles moving up the electric field gradient (positive DEP) and down the electric field gradient (negative DEP) were compiled as a function of frequency and medium conductivity, then compared with spherical core-shell models for DEP polarization in order to calculate core and shell dielectric permittivity and conductivity for comparison with the literature.  This data is useful for dynamic assembly applications for these biocompatible nanoparticles.