The Flanders group fabricates nano-electronic devices for measuring electro-mechanical properties at selected sites on living cells.  The directed electrochemical nanowire assembly (DENA) technique allows us to grow both crystalline metallic and amorphous polymeric nanowires at specific locations and along user-chosen growth paths on micro-electrode arrays.   Nature employs dendritic solidification to grow precisely structured crystals (e.g. snowflakes). DENA harnesses this process to fabricate near single crystalline metallic (Co, Ni, Pd, Pt, Au, Ag, In, or Pb) nanowires.  Lacking crystallinity, polymeric (polypyrrole and polythiophene) wires cannot grow via dendritic solidification, but DENA creates an effective channel through which the wire grows.  The channel is defined by the applied electric field in the solution-filled electrode gaps on the array, so the user controls the wire-growth path by controlling the electric field.   We use the DENA-grown wires as nanoelectrodes for probing the electro-mechanical properties of living cells.  Non-invasive contact between the wire-tips and the cells is accomplished by inducing the cells to attach themselves to the wires rather than the user forcing the electrode into contact with the cells.  This process is called voltage induced cellular adhesion.  Current projects focus on measuring the force exerted at single adhesion points by migrating Dictyostelium cells; identification of the adhesion molecules on the surface of the cells; determining the role of ion flux through channels at the adhesion site; developing nanoscale thermometers to map the thermal landscape within single cells.  Additionally, we are working to produce new types of synthetic nanowires, particularly biological materials like actin filaments.  Summer research projects will involve hands-on training in the microscopy, cell culturing, electronics fabrication, nanoscale polymer synthesis, and electron imaging aspects of these projects.    

Dr. Bruce Law:  Polarizable Ions at Interfaces

Email: bmlaw@phys.ksu.edu

The behavior of ions at surfaces (eg. the water/air surface) has remained a mystery for over one hundred years. It has been found from experiment and computer simulations that larger more polarizable anions (eg. bromide and iodine) are attracted to the interface while the smaller less polarizable anions (eg. fluoride) are repelled from the interface. In this project, we will investigate this effect using the surface sensitive optical technique of ellipsometry to see what effect ion concentration, cation type, anion type and solvent have on the ellipsometric signal.

Dr. Chris Sorensen:  Nanoparticle Solutions

Email: sor@phys.ksu.edu

We have developed chemical methods to create nanoparticles (NP) of gold, silver, CdS, etc that are essentially all the same size (3 to 8 nm). Because of this size uniformity and the fact that the NPs are coated with a surface ligand, suspensions of these NPs act like solutions with temperature reversible aggregation. The summer project would involve measuring the saturated solution concentration versus temperature for a variety of NPs. We would ask how this solubility depends on NP size, surface ligand, solvent, etc. This is a good project at the interface between physics and chemistry.