Figure 2.

Four basic droplet operations on a DMF device. (a) Droplet dispensing is a two-step process. Initially, a finger of liquid is pulled out from the reservoir. A voltage is then applied to both the reservoir and the electrode the liquid finger has reached; effectively pulling the liquid in opposing directions. (b) Droplet movement occurs by turning on an adjacent electrode to the one the droplet is on. (c) A peptide bond formation reaction occurs after droplet merging. Two droplets containing boc-glycine 4-nitrophenyl ester (right hand side droplet) and L-lysine (left hand side droplet), respectively, are brought together and mixed. The yellow side product seen upon formation of the peptide bond is caused by the 4-nitrophenol leaving group. Images for this experiment were adjusted to achieve good contrast and remove colour cast. (d) Droplet splitting is achieved by the step-wise and simultaneous charging of electrodes at opposite sides of a droplet, thereby stretching the droplet in opposite directions until it splits. The scale bars are 1 mm.