  In the recent years, there has been a growing interest in droplet-based
(digital) microfluidics for which, reliable means of droplet manipulation are
required. In this study we demonstrate thermal actuation of droplets on liquid
platforms, which is ideal for biochemical microsystems and lab-on-chip
applications because droplets can be transported with high speed, good control
and minimal thermal loading as compared to using conventional solid substrates.
In addition, other disadvantages of using solid surfaces such as evaporation,
contamination, pinning, hysteresis and irreversibility of droplet motion are
avoided.
  Based on the theoretical development and measurements, a silicon-based
droplet transportation platform was developed with embedded Titanium micro
heaters. A shallow liquid pool of inert liquid (FC-43) served as the carrier
liquid. Heaters were interfaced with control electronics and driven through a
computer graphical user interface. By creating appropriate spatio-temporal
thermal gradient maps, transport of droplets on predetermined pathways was
successfully demonstrated with high level of robustness, speed and reliability.
  The video shows normal imaging of droplet manipulation accompanied by the
corresponding infrared thermal imaging showing the spatio-temporal temperature
maps and the outline of the drop as it moves towards hot spots.
