Evaporation management in digital microfluidic devices

A microfluidic apparatus comprising:

• a first plate comprising a first hydrophobic layer;
• a second plate comprising a second hydrophobic layer;
• an air gap formed between the first hydrophobic layer and the second hydrophobic layer;
• a sensor configured to detect a change in an optical intensity of a reaction droplet within the air gap;
• a controller configured to:
• determine when a volume of the reaction droplet falls below a threshold based on the change in the optical intensity, wherein the reaction droplet comprises a solvent and reaction reagents;
• introduce a replenishing droplet into the air gap of the microfluidic apparatus, wherein the replenishing droplet comprises a solvent;
• and
• combine the replenishing droplet with the reaction droplet after the volume of the reaction droplet falls beneath the threshold.

A microfluidic apparatus configured to replenish in a reaction droplet to correct for evaporation within an air gap formed between a pair of hydrophobic layers, the apparatus comprising:

• a camera configured to monitor a size of a reaction droplet in the air gap;
• and
• a controller coupled to the camera and configured to:
• determine when the size of the reaction droplet falls below a threshold, wherein the reaction droplet comprises a solvent and reaction reagents;
• introduce a replenishing droplet into the air gap of the microfluidic apparatus, wherein the replenishing droplet consists of solvent;
• and
• move the replenishing droplet to combine the replenishing droplet with the reaction droplet after the size of the reaction droplet falls below the threshold.