An apparatus for processing a biological and/or chemical sample in an aqueous liquid droplet, the apparatus comprising: a processing compartment and a liquid medium disposed in said processing compartment; wherein said processing compartment is defined by a reservoir and an immobilisation member (4, 7), wherein said reservoir is defined by a circumferential wall and a base; wherein said liquid medium is (i) immiscible with said liquid droplet, and (ii) of a lower surface energy than the liquid of the liquid droplet; wherein said immobilisation member is (i) arranged within said reservoir, and (ii) comprises a surface; wherein the surface is patterned in such a way that it comprises at least one predefined immobilisation area; and wherein the liquid medium entirely covers the patterned surface of the immobilisation member (4, 7); (a) the at least one predefined immobilisation area within said surface is (i) of a higher surface energy than said liquid medium, (ii) of a higher surface energy than the remaining surface, and (iii) of a sufficient surface energy and a sufficient width in the plane of the surface to allow, in said liquid medium, the immobilisation of the liquid droplet on the at least one predefined immobilisation area via interfacial interactions; and (b) the remaining surface is of at most the same surface energy as said liquid medium, wherein said predefined immobilisation area within said patterned surface is characterised by an advancing contact angle for water that is at least 5 ° lower than the advancing contact angle for water of the remaining surface; and wherein said predefined immobilisation area within said patterned surface is characterised by an advancing contact angle for water that is at least 5 ° lower than the advancing contact angle for water of the said liquid medium. a processing compartment and a liquid medium disposed in said processing compartment; wherein said processing compartment is defined by a reservoir and an immobilisation member (4, 7), wherein said reservoir is defined by a circumferential wall and a base; wherein said liquid medium is (i) immiscible with said liquid droplet, and (ii) of a lower surface energy than the liquid of the liquid droplet; wherein said immobilisation member is (i) arranged within said reservoir, and (ii) comprises a surface; wherein the surface is patterned in such a way that it comprises at least one predefined immobilisation area; and wherein the liquid medium entirely covers the patterned surface of the immobilisation member (4, 7); (a) the at least one predefined immobilisation area within said surface is (i) of a higher surface energy than said liquid medium, (ii) of a higher surface energy than the remaining surface, and (iii) of a sufficient surface energy and a sufficient width in the plane of the surface to allow, in said liquid medium, the immobilisation of the liquid droplet on the at least one predefined immobilisation area via interfacial interactions; and (b) the remaining surface is of at most the same surface energy as said liquid medium, (a) the at least one predefined immobilisation area within said surface is (i) of a higher surface energy than said liquid medium, (ii) of a higher surface energy than the remaining surface, and (iii) of a sufficient surface energy and a sufficient width in the plane of the surface to allow, in said liquid medium, the immobilisation of the liquid droplet on the at least one predefined immobilisation area via interfacial interactions; and (b) the remaining surface is of at most the same surface energy as said liquid medium, wherein said predefined immobilisation area within said patterned surface is characterised by an advancing contact angle for water that is at least 5 ° lower than the advancing contact angle for water of the remaining surface; and wherein said predefined immobilisation area within said patterned surface is characterised by an advancing contact angle for water that is at least 5 ° lower than the advancing contact angle for water of the said liquid medium.