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Micro and nanomechanical resonators represent a promising platform for proteins label-free detection because of their extreme sensitivity, fast response and low cost. Micro-pillars are columnar resonators that can be easily arranged in dense arrays of several thousand sensors in a squared mm. To exploit such a large density, however, a method for tracking independently micropillars resonance frequency is required. Here we present a detection method based on CCD imaging and software image analysis, which can measure the resonance frequency of tens of pillars in parallel. Acquiring simultaneously the frequency shift of up to 40 sensors and applying a proper statistical analysis, we were able to overcome the variability of the single measures improving the device sensitivity at low analyte concentration range. As a proof of concept, this method has been tested for the detection of a tumor marker, the Prostate Specific Membrane Antigen (PSMA). Pillars have been functionalized with an antibody against PSMA. The tumor marker (PSMA) has been detected in a range of concentrations between 300 pM and 100 nM, in buffer and in diluted bovine serum. The sensitivity of our method was limited only by the affinity constant of the antigen–antibody recognition. Moreover, this detection technique demonstrated to be effective in the 1–6 nM range, which is the window of PSMA concentration of clinical interest.

Micro- and nano-mechanical resonators such as cantilevers and pillars are more and more used as molecular sensors, due to their high sensitivity, ease of fabrication and high throughput. In order to modify their wetting properties and to prepare them for the selective adsorption of the molecules of interest, the sensor active surface has to be properly functionalized. This can significantly affect their mechanical performances. In this paper we report on the effect on a micropillar array of different hydrophobic treatments, based on plasma deposition of a fluorocarbon film (FCF) and on the formation of an alkanosilane coating, to obtain a superhydrophobic state. Each treatment was characterized by measuring the change of the quality factor in vacuum, the static contact angle and evaluating the compatibility with gold deposition, to create a bio-functional layer. As case study, DNA self assembled monolayer (SAM) formation and hybridization efficiency were measured. Finally, the superhydrophobicity was tested with diluted human plasma, as preliminary step toward the use of micropillars for biomolecular detection in human samples. (C) 2014 Elsevier B.V. All rights reserved.

Hot spots are defined as nanostructures of noble metal able to locally enhance the electromagnetic field of several orders of magnitude and to confine this effect to a region for several orders of magnitude smaller than the light wavelength. Hot spots are particularly important for the surface enhanced Raman spectroscopy applications, in which the field enhancement is used to amplify the usually weak Raman scattering signal. The hot spots are mostly generated between two or more plasmonic nanostructures separated by nanometric gaps. Several strategies are used to design and realize the hot spots, both in solution, using the noble metal nanoparticles, and on surfaces, using nanolithography and evaporation. In this paper, we demonstrated the fabrication of a nanomechanical plasmonic device for Raman spectroscopy, in which the hot spots are switched on when biased at the resonant frequency and switched off when the actuation signal is removed. Published by AIP Publishing.

In this paper, we present a novel approach toward the fabrication of mechanical oscillators with a local chemical functionalization with subnanometric control. Our method exploits the reactivity of the freshly cleaved surfaces that form when a monocrystalline silicon microstructure is cleaved. The surfaces that form after the cleave expose an atomically smooth Si(111) surface which, if a suitable chemical environment is provided, could undergo to a cycloaddition process that create stable, local and specific chemical bonds. Here, we demonstrated the feasibility of such a scheme on a twin cantilevers geometry, we prove the effective selectivity and stability of the cycloaddition process and we provide experimental evidence that below a critical size, the cleavage procedure creates step free atomically flat silicon surfaces.

The design and characteristics of a micro-system for thermogravimetric analysis (TGA) in which heater, temperature sensor and mass sensor are integrated into a single device are presented. The system consists of a suspended cantilever that incorporates a microfabricated resistor, used as both heater and thermometer. A three-dimensional finite element analysis was used to define the structure parameters. TGA sensors were fabricated by standard microlithographic techniques and tested using milli-Q water and polyurethane microcapsule. The results demonstrated that our approach provides a faster and more sensitive TGA with respect to commercial systems.

Pillars resonators arrays are emerging as powerful sensors for their peculiar characteristics, namely high mass sensitivity, high active areas density and operation in liquid. On the other hand, their characteristic vertical geometry and fabrication strategy hinders a direct integration within integrated circuits. So far, the examples reported in literature are based on a bulk piezoelectric actuation and optical lever detection, which are not suitable for further integration. In this paper we report on the design, fabrication and characterization of Kelvin polarization force actuated pillar resonator. This work represents the first step toward a full integration of pillars with on-chip electronic actuation and detection. (C) 2013 Elsevier B.V. All rights reserved.

Mechanical oscillators became a main focus of research in recent years for potential applications in biomolecule detectors. We recently demonstrated the feasibility of a scheme based on twin cantilevers with a sensitivity down to the single molecule. This approach is extremely promising under the condition that the two terminals of the device can be functionalized with high selectivity and nanometric accuracy by linker molecules. Here we demonstrate a chemo-mechanical method to achieve the intrinsically aligned functionalization of two silicon surfaces, which can be separated by a gap controllable with nanometric precision. The chemical binding of the target molecules in the selected position is obtained through a cycloaddition reaction which exploits the reactivity of the freshly cleaved surfaces that form when the cantilever gap is created. The general validity of this approach is shown by the use in different chemical environments of two compounds with different reactive functional groups.