This work is aimed to conceive, study and implement advanced configurations of Lab-on-Fiber, to provide valuable technological platforms for novel sensor applications. The basic idea is the integration of fiber optic technology with advanced micro-and nano-fabrication technologies to obtain a large set of unique and unconventional functionalities for novel photonic, thermal, mechanical, acoustic, chemical and biological devices, components and systems. The application of optical fibers to the sensing field have been already demonstrated through the so-called Long-Period Fiber Gratings (LPFG), which represent a well assessed in-fiber technology [1, 2]. In this work an on-fiber technology was developed in order to exploit the application of a new generation of LPFG based on the interaction of an evanescent wave of the propagating light with a periodically patterned overlay. To this aim, D-shaped optical fibers were adopted as fiber substrate, and the Focused Ion Beam technology was used for the on-fiber nanopatterning. The flexibility of the adopted fabrication method could allow the realization of innovative LPFGs to be adopted as technological platform for a multitude of chemical sensing applications, depending on the nature of the material deposited onto the flat surface of the etched D-fiber. In contrast to standard single-mode fibers, a D-fiber (Fig. 1) is composed of a germania-doped core, a fluorine-doped cladding, and an undoped supercladding. The core is elliptical in shape, about 4× 2 µm2 in size, and is located approximately 13 µm below the flat surface. The D-fiber is a well-suited platform, as it provides: i) a flat surface to facilitate …