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The D-trehalose/D-maltose-binding protein (TMBP), a monomeric protein of 48 kDa, is one component of the trehalose and maltose (Mal) uptake system. In the hyperthermophilic archaeon Thermococcus litoralis, this is mediated by a protein-dependent ATP-binding cassette system transporter. The gene coding for a thermostable TMBP from the archaeon T. litoralis has been cloned, and the recombinant protein has been expressed in E. coli. The recombinant TMBP has been purified to homogeneity and characterized. It exhibits the same functional and structural properties as the native one. In fact, it is highly thermostable and binds sugars, such as maltose, trehalose and glucose, with high affinity. In this work, we have immobilized TMBP on a porous silicon wafer. The immobilization of TMBP to the chip was monitored by reflectivity and Fourier Transformed Infrared spectroscopy. Furthermore, we have tested the optical response of the protein-Chip complex to glucose binding. The obtained data suggest the use of this protein for the design of advanced optical non-consuming analyte biosensors for glucose detection.

La presente invenzione riguarda l’utilizzo di materiale organico nella fabbricazione di dispositivi optoelettronici a cristalli liquidi in grado di indurre l’allineamento desiderato delle molecole del mezzo liquido cristallino. Il materiale organico biologico, in particolare proteine purificate da micro-organismi, è depositato, quale substrato allineante, con tecniche adeguate su materiali di supporto di comune utilizzo nei dispositivi basati sui cristalli liquidi, quali vetro e materiali semiconduttori. L’invenzione descrive inoltre la realizzazione di alcuni dispositivi ottici che utilizzano gli strati molecolari considerati.

Biosensors have by far moved from laboratories benches to the point of use, and, in some cases, their represent technical standards and commercial successes in applications of social interest, such as medical diagnostic or environmental monitoring. Based on biological molecules, but also on their bio-inspired synthetic counterparts, biosensors employ different transducers (optical, potentiometric, volt-amperometric, colorimetric, and so on) converting the molecular interaction information into a measurable electric signal. As the result of a real multi-disciplinary field of science and technology, biosensors can take advantage from each improvement and progress coming from other disciplines: new features and better performances have been reached in the last year due to simplified fabrication methodologies, deep integration of optical or electrical transducers, and, last but not least, microfluidic circuits. More recently, nanostructured components dramatically increased biosensors reliability especially in public health and environmental monitoring. Nevertheless, there is still a pressing demand of innovations which could lead to smaller, faster, and cheaper biosensors systems with ability to provide not only accurate information but also feedback actions to the real world. The fabrication of a new generation of hybrid biodevices, where biological, or bio-inspired, molecules are fully integrated with a micro or a nano technological platform, strongly depends on the bio-compatibilization treatments of the devices surfaces. The design and the realization of bio/non-bio interfaces with specific properties, such as chemical stability, wettability, and biomolecules immobilization ability, are key features in the miniaturization and optimization processes of biosensors. In particular, protein immobilization is a hot topic in biotechnology since commercial solutions, as in the case of DNA microarrays, are not still available. Proteins are, due to their composition, a class of very heterogeneous macromolecules with variable properties. For these reasons, it is extremely difficult to find a common surface suitable for different proteins with a broad range in molecular weight and physical-chemical properties such as charge and hydrophobicity. A further aspect is the orientation of the bound proteins, that could be of crucial relevance for quantitative analysis, interaction studies, and enzymatic reactions. Many different surfaces, and chemical treatments of these surfaces, have been investigated in the last years, but an universal solution for all the applications aforementioned could not be identified. Following this very actual theme, our main focus in this chapter is to discuss different applications in biosensing of a special class of amphiphilic proteins: the hydrophobins. These proteins self-assemble in a nanometric biofilm at the interfaces between water and air, or on the surfaces covered by water solution. New functionalities can be added to the biosensors surfaces without using any chemical or physical treatment, just covering them by a self-assembled protein biofilm. The main topics covered in the following paragraphs are: origin and properties of the hydrophobins; deposition methods of the hydrophobins biofilm on different surfaces and the characterizations techniques we use to determine the physical properties of these bio-interfaces; the features exhibited by the hydrophobins covered surfaces, and finally, the biosensors systems based on hydrophobins biofilms. We outline in this chapter how the peculiarities of these proteins can be of interest in the technological field, beyond their large utilization in biotechnology, nowadays at industrial level. Moreover, the experience matured on this subject can be the paradigm of a new kind of approach in design and realization of the next generation of biosensors.

All-optical networking can be the sole approach to provide the huge bandwidth required for future networks. The essential elements in such an optical network are optical switches. A number of options have been proposed in order to implement them efficiently. We focus on thermo-optical switches. First, the physical principles of the thermo-optic effect are briefly introduced. A description of the most common technologies used for the fabrication of thermo-optic switches is provided along with the values of thermo-optic coefficient for a number of materials. The main steps useful in order to design thermo-optical switches are also briefly introduced. Finally, a bird's-eye view of the main and recent proposals of switches based on the thermo-optic effect is reported and their performances compared.

In this article, the realization and characterization of a new kind of resonant cavity enhanced photo-detector, fully compatible with silicon microelectronic technologies and working at 1.55 mu m, are reported. The detector is a resonant cavity enhanced structure incorporating a Schottky diode, and its working principle is based on the internal photo-emission effect. A comparison between a Schottky diode (Al/Si or Cu/Si) and the Schottky diode fed on a high-reflectivity Bragg mirror is carried out. Considering Al as Schottky metal, no difference in responsivity is obtained; considering Cu as Schottky metal, a three-fold responsivity improvement is experimentally demonstrated.

Development of non-volatile memories based on organic soft materials is one of two main trends in industry for flash-memories. The electrical bistability of such materials makes them ideal candidates for cost-effective, fast programming switching devices. SiO2-Rose Bengal (bis-triethylammonium) hybrid thin films are reported here together with their characterizations. The technology yields well reproducible films with good current-voltage switching characteristics. Owing to their physical and chemical stability the films are suited to standard micro-photolitography technology, rendering their fabrication cost-effective.

The study and development of Structural Health Monitoring (SHM) systems for aerospace applications is one of the best challenges for the research in the field of fiber optic (FO) sensors. The harsh environments in which these aerospace structures have to work are the major limit for the employment of standard fiber optic sensors for the thermo-mechanical monitoring processes. Thermal loads which act on these structures do not allow using standard fiber optic sensors used for classic avionics application. In fact, many aerospace structures can be exposed to temperatures up to 1000°C, higher than the operation temperature of the standard fiber optic sensors.

Light passing through a photonic crystal can undergo a negative or a positive refraction. The two refraction states can be functions of the contrast index, the incident angle and the slab thickness. By suitably using these properties it is possible to realize very simple and very efficient optical components to route the light. As example we present two devices: a passive device acting as a polarizing beam splitter and a tunable switch. In the first device TM polarization is refracted in positive direction whereas TE component is negatively refracted, in the second device the light is positively refracted at room temperature and negatively refracted varying the local temperature of the device.

In this work, we have compared the optical characteristic of two different photonic dielectric multilayers based on the porous silicon technology. We designed and realized two models devices: a Bragg mirror and the S6 Thue-Morse sequence. Both the structures have the same thickness, the same porosity, and even the same number of the layers but differently spatially ordered. We demonstrate that the two arrangements of the layers influence not only the optical features of these interferometric devices but also their sensitivity when used as optical sensors. We have measured the change of the reflectivity spectra of the devices on exposure to several organic compounds. The experimental results demonstrated that the Thue-Morse aperiodic structure is more sensitive than the Bragg device due to a higher filling capability.

The interaction between an analyte and a biological recognition system is normally detected in biosensors by the transducer element which converts the molecular event into a measurable effect, such as an electrical or optical signal. Porous silicon microstructures have unique optical and morphological properties that can be exploited in biosensing. The large specific surface area (even greater than 500 m2/cm3) and the resonant optical response allow detecting the effect of a change in refractive index of liquid solutions, which interact with the porous matrix, with very high sensitivity. Moreover, the porous silicon surface can be chemically modified to link the bioprobe which recognize the target analytes, in order to enhance the selectivity and specificity of the sensor device. The molecular probe we used was purified by an extremophile organism, Thermococcus litoralis: the protein is very stable in a wide range of temperatures even if with different behavior respect to the interaction with the ligand.

Porous silicon multilayered microstructures have unique optical and morphological properties that can be exploited in chemical and biological sensing. The large specific surface of nanostructured porous silicon can be chemically modified to link different molecular probes (DNA strands, enzymes, proteins and so on), which recognize the target analytes, in order to enhance the selectivity and specificity of the sensor device. We designed fabricated and characterized several photonic porous silicon-based structures, which were used in sensing some specific molecular interactions. The next step is the integration of the porous silicon-based optical transducer in biochip devices: at this aim, we have tested an innovative anodic bonding process between porous silicon and glass, and its compatibility with the biological probes.

Development of memories based on organic soft materials is a current industrial niche aimed at the upper contacts flash memories. The electrical bistability of such materials makes them ideal candidates for cost-effective, fast-programming switching devices. Hybrid thin films Of SiO2 with Rose Bengal (bis-triethylammonium) dopant are here reported for the first time, together with their characterisations. Technology-wise the main advantage of the films is the possibility to cast photolithographically, which is also cost-effective. The physical and chemical stability of the films yields reproducible devices, from both the micro technological and electrical point of view.

The compatibility of porous silicon and anodic bonding technologies for the realization of sensing micro-components in lab-on-chip applications is demonstrated. In particular, we have developed and tested an innovative anodic bonding process: voltage, time and temperature. have been properly matched in order not to affect the properties of the transducing material, which can be strongly modified by thermal treatments through oxidation. Two devices for chemical and biological sensing have been designed, fabricated and tested. The results obtained are very promising, especially regarding further integration of porous silicon and glass with optical and microelectromechanical instruments.

Small analytes such as glucose, L-glutamine (Gln), and ammonium nitrate are detected by means of optical biosensors based on a very common nanostructured material, porous silicon (PSi). Specific recognition elements, such as protein receptors and enzymes, were immobilized on hydrogenated PSi wafers and used as probes in optical sensing systems. The binding events were optically transduced as wavelength shifts of the porous silicon reflectivity spectrum or were monitored via changes of the fluorescence emission. The biosensors described in this article suggest a general approach for the development of new sensing systems for a wide range of analytes of high social interest.

In this paper, the design of a resonant cavity enhanced photodetector, working at 1.55 mu m and based on silicon technology, is reported. The photon absorption is due to the internal photoemission effect over the Schottky barrier at the metal-silicon interface. The photodetector is composed of a silicon layer in between multiple layers of Si-SiO2, as a bottom mirror, and a thin Au film and dielectric coating, as a top mirror. In order to estimate the quantum efficiency, we take advantage of the analytical formulation of the internal photoemission effect (Fowler theory) and its extension for thin films, while for the optical analysis of the device, used to calculate mirror reflectivities and active layer absorptance, a numerical method based on the transfer matrix method has been implemented. Our numerical results prove a significant enhancement of the efficiency obtained at resonant wavelengths by a very thin absorbing layer.