  A droplet position sensing scheme for monitoring multiple droplets has been
proposed, which gives a direct voltage output linearly proportional to droplet
position in electrowetting-on-dielectric (EWOD) based devices. An extra
dielectric and metal layers are required in the bottom substrate for physical
realization of the scheme which provides better isolation between actuation and
sensing line. The capacitors formed due to the extra dielectric and metal
layers facilitate direct voltage output proportional to droplet position during
transport. Energy-based model has been used for analysis purpose. Results show
that the additional dielectric and metal layer in the bottom substrate does not
significantly change the driving electrostatic force profile. This makes the
proposed scheme compatible for digital microfluidic operations.
