The OpenDrop device has four electrodes that can be heated to potentially control the temperature of the liquid drop. On the bottom side of the circuit board a resistor can be placed a cross the through hole of the electrode.
To test I soldered in place two 10 Ohm resisters with a bit of conductive paste underneath and connected them with wires to an external power supply.
To measure the temperature I placed a Open Source Thermal Imager with TFT Display on top. The device uses the MLX90621 array sensor. This sensor could be integrated in a future OpenDrop version to control the temperature contact less.
First measurements showed I quite narrow heating of the electrodes and the liquid placed on top.
The maximum temperature tested was about 80°C on the hottest spot.
The heat distribution was similar with or without liquid drop. Only topless configurations were tested. As a cover glass a ITO coated plastic might be used to prevent temperature spread.