• cantilever
• graphene
• polymer
• rGO
• spiropyran

The idea at the base of this Thesis is to exploit the micromovements induced by light in photochromic-doped polymers for strain engineering of two-dimensional materials (2DMs). Due to to their low dimensionality, 2DMs have peculiar mechanical properties, including stretchability. Thus, it is possible to induce large mechanical strain to such crystals, strongly perturbing the band structure of these materials and modifying their electronic and photonic properties without breaking the lattice. Before a direct application of photochromic-doped polymers for strain engineering of graphene, however, an extensive characterization of how the light response of photochromic-based polymers changes when interacting with graphene is needed. In this Thesis work, variations induced by light on a cantilever structure made of doped-polymer and two different 2DMs are investigated. As dopant, a photochromic molecule that belongs to the family of spiropyrans is used, together with PMMA as polymer matrix. Light-responsivity of the spiropyran-doped PMMA is investigated when put in contact with CVD monolayer graphene or reduced Graphene Oxide (rGO). Using rGO, bilayer rGO/doped-polymer cantilevers with different rGO coverages have been successfully realized and characterized. Light wavelength and intensity dependences of the bending behaviour have been investigated and discussed in the work. A linear dependence between cantilever temperature and light intensity has been observed, evidencing a photo-thermal actuation mechanism. A light-induced displacement of tens of microns of a 10-mm bilayered cantilever system has been measured, varying wavelength and laser intensity. A bending as large as 100 μm has been observed using a UV light (380-405 nm). For its dependence on light intensity and wavelength, bilayer rGO/spiropyran-doped PMMA could find relevant applications in microrobotics and biomimetics systems.