Modulated dynamics of single molecules under electrokinetically-driven confinement

Single molecule nanofluidic technologies would benefit greatly from increased capacity to gain in situ control of confined analytes and allow rapid time modulation of confinement. While lid deflection strategies introduce limited ability to vary vertical confinement (i.e., by using a piezo controlled lens-pusher or pneumatic pressure to depress the top confining device surface), lid deflection is fundamentally mechanical in nature, limiting the modulation times that can be achieved and inducing bulk flows during actuation. We recently demonstrated a new type of nanofluidic technology, electrokinetic confinement, that performs single molecule capture, confinement and manipulation using free energy landscapes derived from nanopatterned AC electric fields via the electrokinetic forces induced on charged analytes. This approach was achieved by placing an AC voltage bias between an upper electrode and a lower electrode coated with a nanopatterned dielectric layer. The electric field is concentrated at the nano-openings in the nanopatterned layer, giving rise to field funnels that form free-energy traps. The use of high frequency AC driving confers robustness against electrolysis. We find a simple “on/”off” modulation of the bias, can be used to capture and release a range of analytes (dsDNA, phospholipid vesicles, self-assembled nanotubes). More complex time-modulation manipulation such as stochastic and periodic forcing can be induced via amplitude modulation. We use these capabilities to study the non-equilibrium dynamics of dsDNA across arrays of modulated electrophoretic well traps.