Abstract: The application relates to a device for collecting a sample of intestinal fluid comprising a polymeric inner material having an at least partially compressed open cell structure, having a volume Vi and being suitable for swelling to a volume greater than or equal to 1.1×Vi by absorbing intestinal fluid, said material being encased with an elastic polymeric casing impervious to digestive fluid, said casing comprising at least one opening allowing the intake of intestinal fluid into the inner material, a gastro-resistant material suitable for dissolving in intestinal fluid at 37° C. being disposed on top of each opening, and at least one mechanism for closing the opening(s).