User:Rsh5932/sandbox

 ** underlined parts are not my work** 

Droplet formation

From an existing droplet (to be added under the original paragraph)

Although the conventional method of creating new droplets through splitting an existing droplet by simply turning the electrodes on and off resulting in droplets of relatively equal volume, the new droplets formed by the conventional method show considerable difference in volume. This difference is caused by local perturbations due to the rapid mass transport. Even though the difference is rather minute and negligible in some applications, it can still pose a problem in applications that are highly sensitive to variations in volume, such as immunoassays and DNA amplification. To overcome the limitation of the conventional method, an existing droplet can be split by gradually changing the potential of the electrodes at the splitting region instead of simply switching them on and off. Using this method, a noticeable improvement in droplet volume variation, from around 10% variation in volume to less than 1% variation in volume, has been reported.

From a reservoir (Just wanted to revise the original paragraph to follow the structure above (conventional method-improvement) and add one more reference to this part. The bold part will be added to the original paragraph. This one doesn't count as my paragraph as I'm merely adding one more reference I found that fits this part.)

Creating a new droplet from a reservoir of liquid can be done in a similar fashion to splitting a droplet. In this case, the reservoir remains stationary while a sequence of electrodes are used to draw liquid out of the reservoir. This drawn liquid and the reservoir form a neck of liquid, akin to the neck of a splitting droplet but longer, and the collapsing of this neck forms a dispensed droplet from the drawn liquid. In contrast to splitting, though, dispensing droplets in this manner is inconsistent in scale and results. There is no reliable distance liquid will need to be pulled from the reservoir for the neck to collapse, if it even collapses at all. Because this distance varies, the volumes of dispensed droplets will also vary within the same device.

Due to these inconsistencies, alternative techniques for dispensing droplets have been used and proposed, including drawing liquid out of reservoirs in geometries that force a thinner neck[16][22], using a continuous and replenishable electrowetting channel , and moving reservoirs into corners so as to cut the reservoir down the middle.[19][22] Multiple iterations of the latter can produce droplets of more manageable sizes.

Droplet Manipulation

Droplet merging

As an existing droplet can be split to form discrete droplets using electrodes, droplets can be merged into one droplet by electrodes as well. Utilizing the same concept applied for creating new droplets through splitting an existing droplet with electrodes, an aqueous droplet resting on an uncharged electrode can move towards a charged electrode where droplets will join and merge into one droplet. However, the merged droplet might not always form a circular shape even after the merging process is over due to surface tension. This problem can be solved by implementing a superhydrophobic surface between the droplets and the electrodes. Oil droplets can be merged in the same way as well, but oil droplets will move towards uncharged electrodes unlike aqueous droplets.

Droplet transportation

Discrete droplets can be transported in a highly controlled way using an array of electrodes. In the same way droplets move from an uncharged electrode to a charged electrode, or vice versa, droplets can be continuously transported along the electrodes by sequentially energizing the electrodes. Since droplet transportation involves an array of electrodes, multiple electrodes can be programmed to selectively apply a voltage to each electrode for a better control over transporting multiple droplets.