a refill droplet facilitates the extraction of a droplet laterally from a channel in a microfluidic apparatus . such extraction allows a discrete band of separated particles or solute molecules to be excised from a fluid stream and processed and analyzed separately . an extraction point is located along the length of the channel and includes an ewod surface or similar microfluidic technology to extract a droplet . an opening in the channel opposite the extraction means is equipped with microfluidic technology to transport a refill droplet to the opening . the refill droplet is moved into the channel or column to occupy the area previously occupied by the extracted droplet . this prevents distortion or mixing of the bands of particles or molecules within the channel and prevents the draining of any portion of the fluidic system .