Here, interconnection technique to link digital microfluidic chips is proposed. Three kinds of digital microfluidic
modules with connecting interface, including flexible module and two types of connector modules, are designed and
fabricated. Since these modules are fabricated on a compliant polymer-based substrate (ITO PET), chip-to-chip droplet
transportation even at different planes can be achieved by the proposed technique. A low-temperature fabrication process
is developed for the polymer substrates, where the SU-8 acts as the insulator. Droplet transportation through
electrowetting on curved surface is confirmed by testing on the bended flexible modules with different curvatures from 0
to 0.06 mm<sup>-1 </sup>at around 70 V<sub>AC</sub>. Then the droplet transportations between flexible and connector modules are investigated.
It is found that the gap size between two modules and the sidewall profiles at interface affect the droplet transportation
directly. For the gap size around 50μm with a smooth perpendicular sidewall profile, 80 V<sub>AC</sub> is shown to actuate droplet
of 1.5 μl, 2.5 μl, or 3.5 μl to cross over the interface successfully.