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Department of Engineering, ICT and Technologies for Energy and Transport Patent Title Method of fabricating structures, starting from material rods. Ref. CNR 10277 Assignee (s): CNR, Centro Fermi Museo della Fisica CNR Institute: IFAC Main Inventor: Andrea Barucci Countries: EP, US Priority date: 15/10/2013 Abstract The present invention refers to a method for the fabrication of optical nanotips for sensing applications. The tips are produced by mechanically rotating and dipping a silica optical fibre in a chemical etching solution (aqueous hydrofluoric acid) with a protection cover layer. Typical tip feature short taper length (~200 μm), tuneable cone angle (up to 40°), and small probe tip dimension (<50 nm). When metal coating is necessary, optical probes with well­defined apertures are obtained. Thanks to the small nanometric roughness of the surface, the metal coating is virtually free of pinholes and presents high adhesion. The probe may be ideal for near field optical imaging and sensing, especially intracellular, applications. Background The improvement of the fabrication technique of nanoprobes originally developed for scanning near­field optical microscopy (SNOM) also harnessed optical fibre nanotip biochemical sensing. The small size of the optical silica nanotips enables intracellular non destructive sensing of physiological and biological processes in the nano­environment, once e.g. proper chemical functionalisation of the tip has been developed. Further increase in the sensitivity of such structures can be obtained by surface enhanced Raman scattering (SERS) or tip enhanced Raman scattering (TERS) measurements. Technology Static etching, owing to its ease of operation, has been widely employed. This technique is however passively driven by the etching solution and the environment, whereas, with the mechanical­chemical technique we developed, the characteristics of the fabricated nanotips can be controlled effectively by changing the rotation parameters of the cuvette and the fibre. Advantages and Applications The mechanical­chemical etching technique has been developed to overcome the problems related to the control of the shape of the meniscus at the interface between the etching liquid and the fibre, which affects directly the symmetry and roughness of the nanotip. By the perfected control of the process, also the surface quality is greatly improved and controlled (e.g. roughness), thus allowing the nanotips to better suit advanced applications. Furthermore, this technology has low cost and is easy to set­up. Applications: SNOM tips, intracellular sensing (pharmaceutical development and cellular physiology), and in general any applications where the surface roughness of material rods must be controlled. Development stage The invention has already been fabricated and tested for the fabrication of nanotips used subsequently in sensing experiments. A functioning prototype is at our laboratories. 31