Mechanical characterization of 3C-SiC grown on Si micromachined cantilever

Resonating microcantilever (MCs) are extremely sensitive mass detectors that have been successfully proposed as chemical, biological and environmental sensors [1]. However, recent works have demonstrated that variation of flexural rigidity due to localization of molecule absorption can induce a positive frequency shift larger than the negative one due to the added mass effect [2]. Goal of our research is to grown and pattern thin 3C-SiC films on Si MC to obtain a huge local increment of beam stiffness, exploiting the outstanding mechanical properties of such material (in particular, its large Young modulus)

Evaluation of different conductive nanostructured particles as filler in smart piezoresistive composites

This work presents a comparison between three piezoresistive composite materials based on nanostructured conductive fillers in a polydimethylsiloxane insulating elastomeric matrix for sensing applications. Without any mechanical deformation upon an applied bias, the prepared composites present an insulating electric behavior, while, when subjected to mechanical load, the electric resistance is reduced exponentially. Three different metal fillers were tested: commercial nickel and copper spiky-particles and synthesized highly-pointed gold nanostars. These particles were chosen because of their high electrical conductivity and especially for the presence of nanosized sharp tips on their surface. These features generate an enhancement of the local electric field increasing the tunneling probability between the particles. Different figures of merit concerning the morphology of the fillers were evaluated and correlated with the corresponding functional response of the composite

Polymeric mask protection for alternative KOH silicon wet etching

A new cost-effective setup for silicon bulk micromachining is presented which makes use of a polymeric protective coating, ProTEKR B2 coating, instead of a conventional hardmask. Different concentrations of KOH and bath conditions (pure, with surfactant, with stirrer, with both surfactant and stirrer) have been considered. ProTEKR B2 coating exhibits good adhesion to Si substrates, no degradation, etching rates and surface roughness comparable to literature data, and etching times greater than 180 min without damaging front side microstructures. Microcantilevers have also been fabricated using two different process flows in order to demonstrate the suitability of such a protective coating in microelectromechanical system (MEMS) technology

A new method to integrate ZnO nano-tetrapods on MEMS micro-hotplates for large scale gas sensor production

A new method, which is easily scalable to large scale production, has been developed to obtain gas sensor devices based on zinc oxide (ZnO) nanostructures with a ‘tetrapod’ shape. The method can be easily extended to other kinds of nanostructures and is based on the deposition of ZnO nanostructures through polymeric masks by centrifugation, directly onto properly designed MEMS micro-hotplates. The micromachined devices, after the mask is peeled off, are ready for electrical bonding and sensing test. Sensor response has been successfully measured for some gases and volatile organic compounds with different chemical properties (ethanol, methane, nitrogen dioxide, hydrogen sulfide)