Control of evaporation in digital microfluidics

A digital microfluidic (DMF) method comprising:

• coating an aqueous reaction droplet with a liquid wax material within an air gap formed between a first hydrophobic layer of a first plate and a second hydrophobic layer of a second plate of a DMF apparatus;
• pinning the liquid wax coating of the aqueous reaction droplet to at least two protrusions within a sub-region of the air gap, thereby distributing the liquid wax around the reaction droplet;
• and
• heating at least the sub-region of the air gap including the coated aqueous reaction droplet, whereby the liquid wax coating limits or prevents evaporation from the aqueous reaction droplet.