A device for processing a sample in a liquid droplet containing a hydrophilic liquid is described. The device includes: a circumferential wall and a base including an immobilisation member. The circumferential wall and the base define a reservoir adapted to accommodate a hydrophobic medium immiscible with the liquid droplet. The medium is of a lower surface energy than a liquid of the liquid droplet. The immobilisation member includes a surface with a plurality of hydrophilic immobilisation areas and a hydrophobic area. The plurality of hydrophilic immobilisation areas is: (a) of a higher surface energy than the medium, (b) of a higher surface energy than the hydrophobic area, and (c) of a sufficient surface energy and a sufficient width to allow, in the medium, immobilisation of liquid droplets on the hydrophilic immobilisation areas via interfacial interactions. Methods of using and rinsing the device are also described.