(222c) Size, Shell Material and Medium Conductivity Dependence on Dielectrophoretic Behaviors of Air Core, Chitosan/Poly-l-Lysine Shell Nanoparticles: Experimental Results

Dynamic (dis)assembly of biocompatible nanoparticles into 3D, packed structures would benefit drug delivery, films and diagnostics.  Dielectrophoretic (DEP) microdevices can rapidly assemble, discriminate, and manipulate polarizable particles within non-uniform electric fields. DEP has primarily discerned micrometer particles; nanoparticles are less explored due to smaller forces that are only an order of magnitude or two larger than Brownian motion. In this work, we examine size and shell material dependencies via DEP of spherical core-shell nanoparticles (CSnp) into 3D particle-assemblies. Two types of CSnp shell materials (chitosan and poly-L-lysine) were custom synthesized around a phospholipid micelle core containing perfluorooctyl bromide oil. For DEP experiments, frequencies from 100kHz to 80MHz at fixed 5Vpp and medium conductivities of 10^-5 and 10^-3 S/m were tested.  The DEP responses of ~220 and 340(or ~400) nm chitosan/poly-L-lysine CSnp were quantified via video intensity densitometry at the microdevice’s quadrupole electrode center, translated into a time averaged relative DEP force, then compared to a spherical core-shell model. The core-shell particles experienced negative DEP across all frequencies, medium conductivities, shell materials and sizes tested. This is attributed to shell and core conductivity and permittivity values less than the medium. Frequency dependent DEP responses revealed a resonance peak between 55MHz-62MHz, which was size and shell material dependent.  This data provides insight into organic shell material properties and is concurrently useful for dynamic assembly applications.