The focus of this research is to characterize the assembly and interactions of biological cells and synthetic particles in AC electric fields using impedance spectroscopy. We have earlier demonstrated how IgG-functionalized latex particles agglutinated with an IgG-specific antigen exhibit a distinguishable impedance spectroscopy response, which can be used for sensing. We are currently investigating the effects of changing media environment parameters on the impedance spectroscopy of yeast/latex particle and yeast/gold nanoparticle suspensions. The yeast/particle suspensions are injected into a 150 micron chamber over interdigitated electrodes of varying gap widths (Figure 1). The impedance and phase angle of the AC field are measured over time at varying frequencies from 1Hz to 1MHz. Preliminary results suggest the agglutination of yeast and particles has a distinct effect on the impedance spectra. In the future, we plan to examine the effects of changing the interdigitated electrode gap geometry on the repeatability of the impedance spectroscopy measurements. The bio-chip impedance spectroscopy technique will then be extended to study the impedance dependence on analyte concentration at higher frequencies (above 1MHz), the effect of using functionalized particles in suspension with yeast cells, and mammalian cell / particle suspensions. The results could be of potential use in new advanced materials, biosensors, and microdevices. Figure 1. Top view and side view of gold nanoparticle / yeast and latex particle / yeast impedance electrode chip. Acknowledgements: NSF-STC for funding.