Manipulating and characterizing individual bio-particles in nanochannels*

Manipulation of matter at the nanoscale and at the single entity level is of utmost importance in a large variety of fields ranging from basic sciences to biology and medicine. It is particularly appealing in order to develop an understanding of complex entities such as viruses, characterize them and assert their biological/chemical function when interacting with other entities in biological fluids. Modern and successful approaches mostly exploit configurations where a strong gradient of field provides a stable attracting potential in space, generated by tightly focused propagating fields or in the near field of antennas. However, due to the volume dependence of their polarizability, sub-100 nm nano-objects require strong and potentially harmful field intensities.

In this work, we transport individual nano-objects in biological level ionic solutions to select locations in on-chip nanochannels using electrokinetic nanovalves. In-between two such nanovalves the nano-object is confined and we study its judiciously restricted thermal motion. The confined particle dynamics is analyzed and provides important properties at the individual nano-object level such as the diffusion coefficient, hydrodynamic diameter, trap stiffness and electrical conductivity of the individual particles. We show the versatility of our system by assessing the properties of polystyrene nanospheres, conjugated polymer nanoparticles and adenoviruses.

The collaborative effect of the applied alternating current (AC) electric field between nanoelectrodes and a designed and fabricated nanochannel topography locally amplifies the near-field gradient, forming together a harmonic trap between a nanovalves system with no-moving-parts effective for various dielectric nanoparticles. This work is an important advancement in manipulating and characterizing individual nano-objects in biologically relevant ionic solutions, including novel medical nanomaterials, or specific viruses.