Micro/nano electro-mechanical systems (MEMS/NEMS) are constantly attracting an increasing attention for their relevant technological applications in fields ranging from biology, medicine, ecology, energy to industry. Most of the performances of micro-nanostructured devices rely on both the design and the intrinsic properties of the constituent materials that are processed at such dimensional scale. For this reason, spatial precision, resolution and reproducibility are crucial factors in the micro-fabrication procedure. 3D direct laser lithography (DLL), based on multiphoton absorption, allows to realize outstanding three-dimensional structures with nanoscale features. This technique has recently emerged as a powerful tool for fabricating 3D micro-patterned surfaces for optics, photonics, as well as for bioinspired cell culture scaffold. We propose a method for a two-step fabrication of micro/nanostructured multicomponent systems to be employed as transductors, by means of the integration of 3D DLL and shadowing effects in metal deposition. A z-axis accelerometer is the proof-of-concept for the validation of the proposed transductor. The former is composed of a cantilever patterned with conductive paths which act as a strain gauge. Mechanical stimulation deforms the cantilever and, accordingly, varies its conductive properties. The fabrication of the conductive components is performed using the vacuum evaporation of gold, a traditional microfabrication technique, and exploiting the shadowing effect due to peculiar microstructures on the cantilever.
A tuning of the light transmission properties of 1D photonic structures employing an external stimulus is very attracting and opens the way to the fabrication of optical switches for colour manipulation in sensing, lighting, and display technology. We present the electric field-induced tuning of the light transmission in a photonic crystal device, made by alternating layers of silver nanoparticles and titanium dioxide nanoparticles. We show a shift of around 10 nm for an applied voltage of 10 V. We ascribe the shift to an accumulation of charges at the silver/TiO2 interface due to electric field, resulting in an increase of the number of charges contributing to the plasma frequency in silver, giving rise to a blue shift of the silver plasmon band, with concomitant blue shift of the photonic band gap. The employment of a relatively low applied voltage gives the possibility to build a compact and low-cost device 1 . We also propose the fabrication of 1D photonic crystal and microcavities employing a magneto-optical material as TGG (Tb3Ga5O12). With these structures we can observe a shift of 22 nm with a magnetic field of 5 T, at low temperature (8 K). The option to tune the colour of a photonic crystal with magnetic field is interesting because of the possibility to realize contactless optical switches 2 . We also discuss the possibility to achieve the tuning of the photonic band gap with UV light in photonic crystals made with indium tin oxide (ITO).
We present the electric field-induced tuning of the light transmission in a photonic crystal device. The device, with alternating layers of Silver and Titanium dioxide nanoparticles, shows a shift of around 10 nm for an applied voltage of 10 V. An accumulation of charges at the Silver/TiO2 interface due to electric field leads to an increase of the number of charges contributing to the plasma frequency in Silver. This results in a blue shift of the Silver plasmon band, with concomitant blue shift of the photonic band gap as a result of the decrease in the Silver dielectric function.
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