A scanning-pipette electrostatic trap for small nanoparticles

01.01.2014, 00:00

Newsletter 7

Although many clever trapping methods have been devised to tame nanoparticles and macromolecules, new methods are still in great demand for hanling different materials and environment. In particular, it is important to achieve contact-free trapping of ever smaller particles down to single proteins or clusters for times beyond seconds. The most established trapping technique, the optical tweezer, loses its effectiveness in this regime because the dipole force scales as the third power of the particle size so that trapping a particle of 10nm diameter requires about a million times more intensity than the commonly trapped micron-sized particles. Last year we developed an electrostatic trap that is created in an aqueous medium between the aperture of a nanopipette and a substrate without any external potential. This is an extension of earlier on-chip work, which used polarization of glass surfaces in water to sculpt an electrostatic potential determined by the nanoscopic geometry. The scannable arrangement of a nanopipette allows us to trap, displace, or release various single particles such as gold nanoparticles and lipid vesicles at will. We plan to use this new technique for plasmonic applications and for trapping single proteins.

Contact: ji-tae.kim(at)mpl.mpg(dot)de
Group: Sandoghdar Division
Reference: J.-T. Kim et al., Nature Communications 5, 3380 (2014).