Microfluidic device with droplet pre-charge on input

1. An electrowetting on dielectric (EWOD) device comprising:

a first substrate and an opposing second substrate defining a gap between the first and second substrates, each substrate including an insulating surface facing the gap;

an array of elements comprising a plurality of individual elements that are actuatable for manipulation of a liquid droplet within the gap, each individual element including a plurality of electrode elements to which actuation voltages are applied; and

a pre-charging structure that includes a channel in fluid communication with the gap and that is configured to receive a fluid reservoir for generation of the liquid droplet, and the pre-charging structure includes an electrical element electrically exposed to the channel;

wherein the electrical element pre-charges the fluid reservoir within the channel, and a portion of the gap containing the liquid droplet spaced apart from the channel is electrically isolated from the electrical element such that the liquid droplet is at a floating electrical potential when located within said portion of the gap;

wherein the pre-charging structure comprises an input structure defining an input channel in fluid communication with the gap, wherein the input channel is the channel that is configured to receive the input of the fluid reservoir, and the electrical element comprises an electrode portion of the plurality of electrode elements that is exposed to the input channel;

wherein the plurality of electrode elements comprises an actuation electrode on the second substrate and a reference electrode on the first substrate, wherein the electrical element is a portion of the reference electrode that is exposed to the input channel; and

wherein the electrode portion and the insulating layer of the first substrate have a stepped configuration at the input channel such that multiple surfaces of the electrode portion are exposed to the input channel.

2. An electrowetting on dielectric (EWOD) device comprising:

a first substrate and an opposing second substrate defining a gap between the first and second substrates, each substrate including an insulating surface facing the pap;

an array of elements comprising a plurality of individual elements that are actuatable for manipulation of a liquid droplet within the gap, each individual element including a plurality of electrode elements to which actuation voltages are applied; and

a pre-charging structure that includes a channel in fluid communication with the gap and that is configured to receive a fluid reservoir for generation of the liquid droplet, and the pre-charging structure includes an electrical element electrically exposed to the channel;

wherein the electrical element pre-charges the fluid reservoir within the channel, and a portion of the gap containing the liquid droplet spaced apart from the channel is electrically isolated from the electrical element such that the liquid droplet is at a floating electrical potential when located within said portion of the gap;

wherein the pre-charging structure comprises an input structure defining an input channel in fluid communication with the gap, wherein the input channel is the channel that is configured to receive the input of the fluid reservoir; and

wherein the electrical element comprises an externally connected pre-charging element that is inserted into the input channel and is located within the input channel spaced apart from the plurality of electrodes.

3. The EWOD device of claim 2 , wherein the pre-charging element comprises an electrical conductor connected to ground.

4. The EWOD device of claim 2 , wherein the plurality of electrode elements includes a reference electrode on the first substrate, and the pre-charging element comprises an electrical conductor that is connected to a same electrical supply that is connected to the reference electrode.

5. The EWOD device of claim 2 , wherein the input channel is defined by an extension of the insulating layer on the first substrate such that no portion of the electrode elements is exposed to the input channel.

6. The EWOD device of claim 1 , wherein the channel comprises an opening cut away through the top substrate to the gap.

7. An electrowetting on dielectric (EWOD) device comprising:

a first substrate and an opposing second substrate defining a gap between the first and second substrates, each substrate including an insulating surface facing the gap;

an array of elements comprising a plurality of individual elements that are actuatable for manipulation of a liquid droplet within the gap, each individual element including a plurality of electrode elements to which actuation voltages are applied; and

a pre-charging structure that includes an input channel in fluid communication with the gap and that is configured to receive a fluid reservoir for generation of the liquid droplet within the gap, and the pre-charging structure includes an electrical element electrically exposed to the channel;

wherein the electrical element pre-charges the fluid reservoir within the channel, and a portion of the gap containing the liquid droplet spaced apart from the channel is electrically isolated from the electrical element such that the liquid droplet is at a floating electrical potential when located within said portion of the gap;

wherein the channel comprises a side opening between the first and second substrates that is in fluid communication with the gap;

wherein the EWOD device further includes a side support that defines a portion of the input channel leading to the side opening; and

wherein the side support is electrically conductive.

8. The EWOD device of claim 1 , further comprising a plurality of offset setting structures in which an electrical element is in electrical connection with the gap, wherein at least one of the offset setting structures is spaced apart from an input structure for inputting the fluid reservoir.