HYDROPHOBIC AFM TIPS BY TWO-PHOTON POLYMERIZATION Carmela De Marcoa, Raffaella Surianoa, Tommaso Zandrinib, Francesca Bragherib, Roberto Osellameb, Marinella Levia and Stefano Turria a Dipartimento di Chimica Materiali e Ingegneria Chimica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan, Italy b Istituto di Fotonica e Nanotecnologie CNR, Piazza Leonardo da Vinci 32, 20133 Milan, Italy Two-photon polymerization (2PP) is an innovative technology for 3D sub-micrometric structuring of photopolymers. A very promising application is the fabrication of polymeric tips for Atomic Force Microscopy (AFM). Currently AFM tips are manufactured with standard microfabrication technologies, employing inorganic materials and requiring expensive facilities. The main advantages of producing polymer AFM tips by 2PP rely on a cheaper manufacturing process along with the appealing capacity to customize AFM tips, in terms of geometry and materials. A recent work describes the synthesis and processing of a new PFPE-based hydrophobic and chemically resistant photoresist, successfully structured by 2PP.[1] Hydrophobic AFM tipsare particularly needed for studying mechanical properties of hydrophilic samples such as hydrogels by means of AFM indentations, in order to reduce capillary forces which produce high tip-sample adhesion.[2] In figure a tip fabricated in PFPE photoresist by 2PP (b) with a contact radius comparable to a commercial colloidal tip (a) is showed. ____ [1] C. De Marco, A. Gaidukeviciute, R. Kiyan, S.M. Eaton, M. Levi, R. Osellame, B.N. Chichkov, S. Turri, Langmuir (2013), 29, 426-431 [2] R. Suriano, C. Credi, M. Levi, http://dx.doi.org/10.1016/j.apsusc.2014.05.108 S. Turri, Applied Surface Science (2014),