  Free-surface electrokinetic flows have been attracting increasing attention
from the research community over recent times, as attributable to their diverse
fields of applications ranging from fluid mixing, particle manipulation to
bio-chemical processing on a chip. Traditional electrokinetic processes
governing free surface flows are mostly effective in manipulating fluids having
characteristically low values of the electrical conductivity (lower than 0.085
S/m). Biological and biochemical processes, on the other hand, typically aim to
manipulate fluids having higher electrical conductivities. To circumvent the
problem of traditional electrokinetic processes in manipulating highly
conductive fluids mediated by free surface flows, here we demonstrate a novel
on-chip methodology for the same by exploiting the interaction between an
alternating electric current and a thermal field. The consequent local
gradients in electrical properties can be tuned to direct the flow towards a
specific direction on the interface, opening up a new realm of on-chip process
control without necessitating the creation of a geometric confinement. Similar
concept of free-surface flow can be used to trigger the fluid along a
open-channel flow
