  In this work, we present an automated platform for trapping and stretching
individual micro- and nanoscale objects in solution using electrokinetic
forces. The platform can trap objects at the stagnation point of a planar
elongational electrokinetic field for long time scales, as demonstrated by the
trapping of ~100 nanometer polystyrene beads and DNA molecules for minutes,
with a standard deviation in displacement from the trap center < 1 micrometer.
This capability enables the stretching of deformable nanoscale objects in a
high-throughput fashion, as illustrated by the stretching of more than 400 DNA
molecules within ~4 hours. The flexibility of the electrokinetic stretcher
opens up numerous possibilities for contact-free manipulation, with size-based
sorting of DNA molecules performed as an example. The platform described
provides an automated, high-throughput method to track and manipulate objects
for real-time studies of micro- and nanoscale systems.
