The present invention provides a vapor-permeable flexible sensing platform unit comprising: a first porous membrane, wherein said membrane is substantially flexible and hydrophobic; and a volatile organic compounds (VOCs) sensor disposed on said membrane, the VOCs sensor comprising an electrode array and a conducting polymer porous film being in electric contact with said electrode array, wherein the VOCs sensor is insensitive to lateral strain. Further provided are a method of preparation of said platform unit and a lift-off, float-on (LOFO) method for the preparation of protonically doped polyaniline (PANI) thin films.