Droplet Actuator Loading and Target Concentration

A droplet actuator comprising a substrate comprising:

• (a) a discrete flow section comprising electrodes arranged for conducting droplet operations on a substrate surface;
• (b) a continuous flow section comprising a fluid path arranged for flowing a fluid therethrough, and separated from the discrete flow section by a barrier;
• (c) an opening in the barrier arranged relative to the electrodes such that fluid in the fluid path is in proximity to one or more of the electrodes;
• and
• (d) a capture surface comprising a component having an affinity for the target substance.

A method of conducting a chemical or biochemical reaction or interaction, the method comprising:

• (a) providing a droplet actuator comprising a substrate comprising:
• (i) a discrete flow section comprising electrodes arranged for conducting droplet operations on a substrate surface;
• (ii) a continuous flow section comprising a fluid path arranged for flowing a fluid therethrough, and separated from the discrete flow section by a barrier;
• (iii) an opening in the barrier arranged relative to the electrodes such that fluid in the fluid path is in proximity to one or more of the electrodes;
• (iv) a capture surface comprising a component having an affinity for the target substance;
• (b) flowing a fluid comprising the target substance through the fluid path;
• (c) capturing the target substance on the capture surface;
• and
• (d) conducting one or more droplet operations using the electrodes to transport a reagent into contact with the target substance and thereby conduct a chemical or biochemical reaction or interaction.

A method of providing a droplet on a droplet actuator, the method comprising:

• (a) providing a droplet actuator comprising a substrate comprising:
• (i) a discrete flow section comprising electrodes arranged for conducting droplet operations on a substrate surface;
• (ii) a continuous flow section comprising a fluid path arranged for flowing a fluid therethrough, and separated from the discrete flow section by a barrier;
• (iii) an opening in the barrier arranged relative to the electrodes such that a droplet from the fluid path passing through the opening comes into proximity to one or more of the electrodes;
• (b) flowing a filler fluid comprising the droplet through the fluid path;
• (c) causing the droplet to pass through the opening into proximity with one or more of the electrodes to permit one or more electrode mediated droplet operations to be performed on the droplet.