The present invention provides a dermal patch for selectively retaining one or more analyte(s) from a body of a subject comprising: a membrane layer (101) for retaining one or more analyte(s) from a body of a subject, with a first and a second side, wherein the first side is adapted to be in fluid communication with the skin of the subject optionally holding means for securing the membrane layer in place an adhesive layer (104) and a backing layer wherein between the backing layer and the membrane layer (101) there is an expandable layer (103) for applying pressure to the membrane layer.
