  Dielectrophoresis is a very promising technique for particle manipulation on
a chip. In this study, we demonstrate a controlled mannuvering of polystryrene
particles on a simple paper-and-pencil based device by exploiting the
underlying electrokinetics with primary contribution from dielectrophoretic
(DEP) forces. On contrary to other reported DEP devices, the present
configuration does not demand a shophitcated laboratory module for creating a
non-uniform electric field, which is essential requirement in DEP settings. We
demonstrate positive dielectrophoresis (pDEP) to trap 1 um size polystyrene
particle for low-conductivity suspending medium, at an applied field strength
of 100 V/cm. In addition, the switching of the trapping direction (positive to
negative dielectrophoresis) can be simply achieved by manipulating the
conductivity of the media. We further bring out an optimum range of pH for
effective particle trapping. These results have significant implications
towards designing cell-on-a-chip based point of care diagnostic devices for
resource limited settings.
