Erika Zanchetta

Stereolithography of SiOC Ceramic Microcomponents

The first example of the fabrication of complex 3D polymer-derived-ceramic structures is presented with micrometer-scale features by a 3D additive manufacturing (AM) technology, starting with a photosensitive preceramic precursor. Dense and crack-free silicon-oxycarbide-based microparts with features down to 200 μm are obtained after pyrolysis at 1000 °C in a nitrogen atmosphere.

Novel hybrid organic-inorganic spin-on resist for electron- or photon-based nanolithography with outstanding resistance to dry etching.

A new spin-on alumina-based resist exhibits excellent performance in terms of both achievable lateral resolution and etch resistance in fluorine-based non-cryo-cooled dry etching processes. The resist has selectivity greater than 100:1 with respect to the underlying silicon during the etching process, patternability with various lithographic tools (UV, X-rays, electron beam, and nanoimprint lithography), and positive and negative tone behavior depending only on the developer chemistry.

Injection molded polymeric micropatterns for bone regeneration study.

An industrially feasible process for the fast mass-production of molded polymeric micro-patterned substrates is here presented. Microstructured polystyrene (PS) surfaces were obtained through micro injection molding (μIM) technique on directly patterned stamps realized with a new zirconia-based hybrid spin-on system able to withstand 300 cycles at 90 °C. The use of directly patterned stamps entails a great advantage on the overall manufacturing process as it allows a fast, flexible, and simple one-step process with respect to the use of milling, laser machining, electroforming techniques, or conventional lithographic processes for stamp fabrication. Among the different obtainable geometries, we focused our attention on PS replicas reporting 2, 3, and 4 μm diameter pillars with 8, 9, 10 μm center-to-center distance, respectively. This enabled us to study the effect of the substrate topography on human mesenchymal stem cells behavior without any osteogenic growth factors. Our data show that microtopography affected cell behavior. In particular, calcium deposition and osteocalcin expression enhanced as diameter and interpillar distance size increases, and the 4-10 surface was the most effective to induce osteogenic differentiation.

Active diffraction gratings: Development and tests

We present the realization and characterization of an active spherical diffraction grating with variable radius of curvature to be used in grazing-incidence monochromators. The device consists of a bimorph deformable mirror on the top of which a diffraction grating with laminar profile is realized by UV lithography. The experimental results show that the active grating can optimize the beam focalization of visible wavelengths through its rotation and focus accommodation.

Active-grating monochromator for the spectral selection of ultrashort pulses

Active gratings have been used to realize a grazing-incidence double-grating monochromator for the spectral selection of ultrashort pulses while preserving the temporal duration by compensating for the pulse-front tilt. The active grating consists of a bimorph deformable mirror on the top of which a diffraction grating with laminar profile is realized by UV lithography. The time-delay compensated configuration has been tested with ultrashort pulses at 800 nm. The feasibility of this configuration for the extreme-ultraviolet spectral region has been demonstrated by ray tracing studies.

Hybrid materials: a bottom-up approach for nanotechnology applications

Engineered organic-inorganic hybrid materials, HyMat, offer new opportunities for the easy, fast and cheap development of miniaturized functional devices. The integration of inorganic oxide networks, organic functional groups and optically active molecules or nanoparticles allows to obtain combinations of properties and structures otherwise impossible with traditional materials. In particular, a simple and highly versatile synthesis platform enabling preparation of HyMat is presented, which is built up by a bottom-up sol-gel approach at low processing temperatures. A few types of key building blocks pave the way for accessing HyMat and make up their formulation, providing a means to synthesize innovative materials enabling to get: - optically active micro and nanostructures; - miniaturized sensors for analytes in gaseous or liquid media; - direct patternability with a range of lithographic techniques; - variable inorganic and organic compositions, and controlled porosity. Examples of micro and nanostructures based on these spin-on materials with ceramic (i.e. SiO2, GeO2, Al2O3, ZrO2, TiO2,) and hybrid compositions will be presented for different applications including plasmonic or fluorescent sensors, dry-etching masks with outstanding resistance, optically active micro and nanostructured platforms and high resolution patterns.

Resins Materials as Alternative Insert for the Fabrication of Micro Structured Surfaces by Micro Injection Moulding

Micro injection moulding is a key technology for mass-production of micro structured surfaces, such as optical and microfluidic devices. The manufacturing of a microstructured master mould with traditional technologies poses challenges about durability, accuracy and high - volume production. This paper introduces a new approach to realize micro mould inserts in a fast and economical way. Suitable engineered materials as alternative inserts to the metallic one are proposed exploiting the following new strategy: a thermosetting epoxy resin from renewable sources was synthesized and used to realize the mould insert via casting. The initial low viscosity of the liquid epoxy resin precursors allows the achievement of a high fidelity replica of different micro structures and provides an inexpensive and convenient route for rapidly duplicate master mould. A staggered harringbone (SHM) micro-mixer geometry was replicated and the epoxy based resin insert withstood 900 moulding cycles showing good features replication and durability.

Development of active gratings for the spectral selection of ultrafast pulses

We present the design, realization and characterization of active deformable gratings for extreme-ultraviolet monochromators for ultrashort pulses. The core device consists of a bimorph deformable mirror on the top of which a diffraction grating with laminar profile is realized by UV lithography. The curvature radius of the grating substrate can be varied changing the voltage applied to an underlying piezo-actuator. The advantage of this technology is to provide gratings with high optical quality, robust, compatible with any coating deposition and realized with only vacuumcompatible materials. We present the characterization of a time-delay compensated monochromator realized with these devices, showing that the active grating can optimize the beam focusing through its rotation and deformation. Two equal active gratings have been mounted in a compensated configuration to realize a grazing-incidence double-grating monochromator for the spectral selection of ultrashort pulses and the simultaneous compensation of the pulse front-tilt given by the diffraction. The wavelength scanning is performed by the first grating through rotation. The radiation is focused on the intermediate plane, where a slit carries out the spectral selection. Finally, the second grating compensates for the pulse front-tilt given by the first one. The spectral focusing of both gratings is maintained at the different wavelengths through the variation of the radii of curvature. The instrument has been tested with a Ti:Sa laser operated at 800 nm. We have been able to demonstrate that the double-grating configuration with active gratings compensates for the pulse front-tilt, that is reduced from 1 ps at the intermediate plane to 100 fs at the output. The final value is limited by the group delay dispersion of the monochromator within the 10-nm bandwidth of the laser. A configuration for the selection on XUV ultrashort pulses has been theoretically studied and the expected performances presented. Active gratings may be considered as a cheaper and more flexible alternative to standard gratings for the realization of extremeultraviolet monochromators for ultrafast pulses, such as free-electron lasers and high-order laser harmonics.