COLL 397 |
| A new scanning probe microscopy approach utilizing AC electrokinetic forces allows for real-time non-contact functional imaging of live cells with nanometer-scale spatial resolution. Dielectrophoresis (DEP) describes the mobility of particles in radio-frequency AC electric fields and is related to the frequency-dependent electric polarizability. Similar to the forces in optical trapping, DEP interactions are greatest for large field gradients, such as those adjacent to highly curved electrodes. These forces have been integrated for the first time into a scanning probe microscope, allowing for ultra-high resolution dielectric characterization of bacterial and mammalian cells. This technique has allowed for the first measurements of the variation in DEP forces across a single bacterial cell. Changing the AC frequency can significantly change the magnitude (and even sign) of the DEP force, allowing for dielectric spectroscopy ranging over a decade in AC frequency in only 1/8 of a second. Spatio-temporal changes in the dielectric spectrum reveal location-dependent and/or time-dependent changes in membrane capacitance and charge mobility. |
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Advances in Nanomedicine
8:30 AM-12:00 PM, Tuesday, 12 September 2006 Sir Francis Drake -- Monterey/Cypress Rooms, Oral
Division of Colloid & Surface Chemistry |