Robotic pill for sampling body cavities. a) Scheme of robotic pill illustrating main components  including i) an absorbent material to capture biomarkers and biofluids, ii) a pH-sensitive  porous membrane and iii) a magnetic core that enables navigation and retention.  b) Scheme illustrating docking of the robotic pill within the intestines in the  presence of an external magnetic field. c) Photograph illustrating the actual size  of the robotic pill. (16 x 6 x 1.5 mm) d) Photograph illustrating sampling liquid  solution using a robotic pill, the top image illustrates dry robotic pill and  bottom the same robotic pill after 1-minute incubation in a blue dye solution.