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DY: Fachverband Dynamik und Statistische Physik
DY 38: Wetting, Micro and Nanofluidics (joint session CPP/ DY)
DY 38.8: Talk
Wednesday, March 18, 2015, 17:00–17:15, C 243
High-throughput and passive trapping of nano-objects using electrostatic forces — •Michael Adrian Gerspach1,2,3, Nassir Mojarad2, Yasin Ekinci2, and Thomas Pfohl1,3 — 1Swiss Nanoscience Institute, Basel, 4056, Switzerland — 2Paul Scherrer Institute, Villigen, 5323, Switzerland — 3Department of Chemistry, University of Basel, Basel, 4056, Switzerland
Contact free trapping of nano-objects in solution is of broad interest. Although several methods have been developed, like optical tweezers, stable and high throughput trapping of nanometer-sized particles remains challenging. Our approach of trapping charged nano-objects is geometry induced electrostatic trapping [1], a method based on altering the surface topology of nano-channels that are negatively charged when exposed to water. Here we present the on chip contact free trapping of single 40 to 80 nm gold particles in nanometer-sized pockets without the use of any externally applied forces. The particles in the solution are pushed into the pockets and trapped only because of the difference in electrostatic potential between the nanofluidic channel walls and the finer pocket structures. Increasing the salt concentration of the solution leads to screening of the surface charges by free counter ions and therefore, weakens the trap strength and shortens the average time a particle dwell in a trap. Thus by chancing the concentration of the solution or the height of the nanofluidic channels, the particles can be trapped from microseconds to several minutes. In future we plan to extend this method to trap and investigate the dynamics of biological entities such as DNA or large proteins. [1] Nature 457 (2010), 692-695