Gate Electrodes Enable Tunable Nanofluidic Particle Traps

The ability to control the location of nanoscale objects
in liquids
is essential for fundamental and applied research from nanofluidics
to molecular biology. To overcome their random Brownian motion, the
electrostatic fluid trap creates local minima in potential energy
by shaping electrostatic interactions with a tailored wall topography.
However, this strategy is inherently static; once fabricated, the
potential wells cannot be modulated. Here, we propose and experimentally
demonstrate that such a trap can be controlled through a buried gate
electrode. We measure changes in the average escape times of nanoparticles
from the traps to quantify the induced modulations of 0.7 kBT in potential energy and
50 mV in surface potential. Finally, we summarize the mechanism
in a parameter-free predictive model, including surface chemistry
and electrostatic fringing, that reproduces the experimental results.
Our findings open a route toward real-time controllable nanoparticle
traps.