Evaporation management in digital microfluidic devices

A method of replenishing a reaction droplet in an air gap region of a microfluidic apparatus to correct for evaporation, the method comprising:

• optically monitoring the reaction droplet by using a camera to image the droplet in the air gap region of the microfluidic apparatus;
• determining a volume of the reaction droplet by from the image of the droplet;
• determining when the volume of the reaction droplet falls below a threshold, wherein the reaction droplet comprises a solvent and reaction reagents;
• introducing a replenishing droplet into the air gap region of the microfluidic apparatus, wherein the replenishing droplet consists of solvent;
• and
• combining the replenishing droplet with the reaction droplet after the volume of the reaction droplet falls beneath the threshold.

A method of replenishing a reaction droplet within an air gap region of a microfluidic apparatus to correct for evaporation, the method comprising:

• monitoring, with a camera, a size of a reaction droplet in the air gap of the microfluidic apparatus;
• determining when the size of the reaction droplet falls below a threshold, wherein the reaction droplet comprises a solvent and reaction reagents;
• introducing a replenishing droplet into the air gap of the microfluidic apparatus, wherein the replenishing droplet consists of solvent;
• and
• combining the replenishing droplet with the reaction droplet after the size of the reaction droplet falls beneath the threshold by applying electrical energy to move the replenishing droplet into contact with the reaction droplet by electrowetting.