Marzia Quaglio

Guided Bloch Surface Waves on Ultrathin Polymeric Ridges

We present a direct evidence of Bloch surface waves (BSWs) waveguiding on ultrathin polymeric ridges, supported by near-field measurements. It is demonstrated that near-infrared BSWs sustained by a silicon-based multilayer can be locally coupled and guided through dielectric ridges of nanometric thickness with low propagation losses. Using a conventional prism-based configuration, we demonstrate a wavelength-selective BSW coupling inside and outside the ridge. Such a result can open interesting opportunities in surface wave-mediated sensing applications, where light could be selectively coupled in specific regions defined by nanometric reliefs.

Bloch surface waves in ultrathin waveguides: near-field investigation of mode polarization and propagation

In this work, we use a multi-heterodyne scanning near-field optical microscope to investigate the polarization and propagation of Bloch surface waves in an ultrathin (∼λ∕10) ridge waveguide. First, we show that the structure sustains three surface modes, and demonstrate selective excitation of each. Then, by numerically processing the experimental data, we retrieve the transverse and longitudinal components of each of the modes, in good agreement with the calculated fields. Finally, we provide an experimental estimation of the effective indices and the dispersion relations of the modes.

Toward Totally Flexible Dye-Sensitized Solar Cells Based on Titanium Grids and Polymeric Electrolyte

In this work, we present a novelty in the dye-sensitized solar cell scenario: a quasi-solid and completely flexible configuration based on plastic substrates and metallic meshes as support. The aim is to obtain a portable efficient device that can be competitive in the solar market due to the low cost and easy-to-prepare materials used for its fabrication. To fulfill this purpose, three different typologies of devices are proposed and tested in order to move from a rigid to a completely flexible setup in a gradual way. Materials and cells have been thoroughly characterized and tested by means of physicochemical, electrical, and electrochemical measurements to investigate the observed performances and the results that are reported in this paper.

Two-dimensional optics on silicon nitride multilayer: Refraction of Bloch surface waves

When properly designed, a dielectric multilayer can sustain Bloch surface waves (BSWs). Using a multiheterodyne scanning near-field optical microscope that resolves phase and polarization, we will show that a thin dielectric structure deposited on the multilayer deflects the BSW propagation according to Snell’s law. Moreover, the mechanism involved in this process is a transfer of energy from the BSW state in the bare multilayer to the new BSW state generated by the presence of the thin dielectric structure. No relevant radiative counterpart occurs. This characteristic validates the treatment of BSWs at the surface of dielectric multilayers as a two-dimensional phenomenon.

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, ProTEK® 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. ProTEK® 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.

Ultrafast room-temperature crystallization of TiO2 nanotubes exploiting water-vapor treatment.

In this manuscript a near-room temperature crystallization process of anodic nanotubes from amorphous TiO2 to anatase phase with a fast 30 minutes treatment is reported for the first time. This method involves the exposure of as-grown TiO2 nanotubes to water vapor flow in ambient atmosphere. The water vapor-crystallized samples are deeply investigated in order to gain a whole understanding of their structural, physical and chemical properties. The photocatalytic activity of the converted material is tested by dye degradation experiment and the obtained performance confirms the highly promising properties of this low-temperature processed material.

Evaluation of different PDMS interconnection solutions for silicon, Pyrex and COC microfluidic chips

One of the most crucial issues in the domain of microfluidics is the chip to world interface. This paper describes a characterization methodology of a quite common microfluidic interconnection scheme, based on polydimethylsiloxane (PDMS), applied to some of the most popular substrates (silicon, Pyrex and cyclic olefin copolymer) for microfluidic applications. Particular emphasis is given to the evaluation of leakage endurance as a function of the main geometrical parameters of the interconnections and the selected bonding technique. Oxygen plasma activation of the PDMS surface and the application of a thin PDMS interlayer demonstrated the most attractive solutions, due to the straightforward approach and limited cost. Maximum sustainable pressures in excess of 200 kPa have been achieved. Results obtained are critically discussed with the aim to outline PDMS interconnection guidelines for different microfluidic applications.

Microwave-Assisted Synthesis of Reduced Graphene Oxide/SnO2 Nanocomposite for Oxygen Reduction Reaction in Microbial Fuel Cells

We report on an easy, fast, eco-friendly, and reliable method for the synthesis of reduced graphene oxide/SnO2 nanocomposite as cathode material for application in microbial fuel cells (MFCs). The material was prepared starting from graphene oxide that has been reduced to graphene during the hydrothermal synthesis of the nanocomposite, carried out in a microwave system. Structural and morphological characterizations evidenced the formation of nanocomposite sheets, with SnO2 crystals of few nanometers integrated in the graphene matrix. Physico-chemical analysis revealed the formation of SnO2 nanoparticles, as well as the functionalization of the graphene by the presence of nitrogen atoms. Electrochemical characterizations put in evidence the ability of such composite to exploit a cocatalysis mechanism for the oxygen reduction reaction, provided by the presence of both SnO2 and nitrogen. In addition, the novel composite catalyst was successfully employed as cathode in seawater-based MFCs, giving electrical performances comparable to those of reference devices employing Pt as catalyst.

Direct Photolithography of Perfluoropolyethers for Solvent-Resistant Microfluidics

In this work, photocurable perfluoropolyethers (PFPEs) have been used for the fabrication of microfluidic devices by a direct photolithographic process. During this mask-assisted photopolymerization technique, the material is directly photopolymerized in the presence of a mask, avoiding the use of a master. We demonstrate the high level of control in transferring micropattern features with high density, a minimum transferred size of 15 μm, a high aspect ratio (at least up to 6.5), and complex shapes useful for microfluidic applications. Moreover, we successfully apply this technology to fabricate sealed devices; the fabrication time scale for the overall process is around 5 min. The devices are able to withstand a flow pressure of up to 3.8 bar, as required for most microfluidics. Finally, the devices are tested with a model reaction employing organic solvents.

A multilevel Lab on chip platform for DNA analysis

Lab-on-chips (LOCs) are critical systems that have been introduced to speed up and reduce the cost of traditional, laborious and extensive analyses in biological and biomedical fields. These ambitious and challenging issues ask for multi-disciplinary competences that range from engineering to biology. Starting from the aim to integrate microarray technology and microfluidic devices, a complex multilevel analysis platform has been designed, fabricated and tested (All rights reserved—IT Patent number TO2009A000915). This LOC successfully manages to interface microfluidic channels with standard DNA microarray glass slides, in order to implement a complete biological protocol. Typical Micro Electro Mechanical Systems (MEMS) materials and process technologies were employed. A silicon/glass microfluidic chip and a Polydimethylsiloxane (PDMS) reaction chamber were fabricated and interfaced with a standard microarray glass slide. In order to have a high disposable system all micro-elements were passive and an external apparatus provided fluidic driving and thermal control. The major microfluidic and handling problems were investigated and innovative solutions were found. Finally, an entirely automated DNA hybridization protocol was successfully tested with a significant reduction in analysis time and reagent consumption with respect to a conventional protocol.