Search

Amino-terminated surfaces can be effectively obtained by means of silanizing agents, realizing surfaces suitable for the purification of biomarkers of several pathologies. Since the level of biomarkers, such as microRNAs and cell-free DNA, into circulation may be extremely low, new and ameliorated capturing molecules and protocols are highly required. In this work, a new silane, acetone-imine propyl trimethoxysilane (AIPTMS), is synthesized with a simple and elegant reaction, via the nucleophilic addition of the primary amino group to the carbonyl group of acetone. AIPTMS and APTMS were used to silanize silicon oxide surfaces, which were characterized chemically (XPS) and morphologically (AFM). The two types of surfaces were chemically similar, but behaved very differently both for surface morphology and functional properties. The AIPTMS-modified surface was indeed very smooth and homogeneous with respect to the APTMS-modified surface. Moreover, the AIPTMS surface captured larger amounts of nucleic acids almost immediately after preparation, while APTMS-based functional surfaces needed longer time to reach comparable efficiency. AIPTMS shows several advantages over standard aminosilanes, as it realizes a more homogeneous surface coverage that, in turn, produces an improved response towards the capture of nucleic acids. AIPTMS is a very promising reagent for the reliable and reproducible preparation of active biofunctional surfaces for the purification and analysis of circulating biomarkers.

With the purpose of designing active patches for photodynamic therapy of melanoma, transparent and soft hydrogel membranes (HMs) have been fabricated by cation-induced gelation of rod-like cellulose nanocrystals (CNCs) bearing negatively charged carboxylic groups. Na+ , Ca2+ , Mg2+ have been used as cross-linkers of cellulose nanocrystal (CNC). The biosafety of this material and of its precursors has been evaluated in vitro in cell cultures. Morphological changes, cell organelles integrity, and cell survival with the tetrazolium salt reduction (MTT) assay were utilized as tests of cytotoxicity. Preliminary investigation was performed by addition of the hydrogel components to the cell culture medium and by incubations of the CNC-HM in direct and indirect contact with a confluent monolayer of A375 melanoma cells. Direct contact assays suffered from interference of physical stress. Careful evaluation of cytotoxicity was obtained considering the overall picture provided by microscopy and biochemical tests performed with the CNC-HM in indirect contact with two melanoma cell lines (A375, M14) and human fibroblasts. CNCs have been demonstrated to be a safe precursor material and CNC-HMs have a good biocompatibility provided that the excess of cations, in particular of Ca2+ is removed. These results indicate that CNC and can be safely used to fabricate biomedical devices such as transparent hydrogel patches, although attention must be paid to the fabrication procedure.

The widely tunable physical and chemical characteristics of hydrogels make them advantageous in biomedical and pharmaceutical applications, yet their hydrophilic nature might discourage their use as drug delivery systems for poorly water soluble molecules. In this work we demonstrate the sustained release of a large amount of a lipophilic drug (clofazimine) from nanocellulose hydrogels. Hydrogels are formed via ionotropic gelation and loaded with up to 37 % w/w) of the hydrophobic molecule. The kinetic profile avoids the initial burst release and we demonstrate that the surfactant co-loading is a successful strategy to increase by about 50 times the drug solubility in water, without the need of complex fabrication steps.

The influence of the physical, rheological, and process parameters on the cellulose nanocrystal (CNC) drops before and after external gelation in a CaCl2 solution was investigated. The dominant role of the CNC’s colloidal suspension properties, such as the viscous force, inertial, and surface tension forces in the fluid dynamics was quantitatively evaluated in the formation of drops and jellified beads. The similarity and difference between the behavior of carbohydrate polymers and rod-like crystallites such as CNC were enlightened. Pump-driven and centrifugally-driven external gelation approaches were followed to obtain CNC hydrogel beads with tunable size and regular shape. A superior morphological control—that is, a more regular shape and smaller dimension of the beads—were obtained by centrifugal force-driven gelation. These results suggest that even by using a simple set-up and a low-speed centrifuge device, the extrusion of a colloidal solution through a small nozzle under a centrifugal field is an efficient approach for the production of CNC hydrogel beads with good reproducibility, control over the bead morphology and size monodispersion.

A ceramic composite was produced by mixing cubic zirconia with graphene nano-platelets. The samples were consolidated by flash sintering in argon atmosphere to avoid the oxidation of graphene at high temperature. The applied electrical field ranged between 50 V cm and 500 V cm, while the current density limit was set between 35 mA mm and 175 mA mm. The presence of the conductor filler reduced the onset flash temperature, and a good densification of the composite was obtained. Remarkably, the same level of densification was not possible on pure cubic zirconia samples (possessing the same geometry) as they got physically damaged at the flash ignition (likely due to internal temperature gradients). After sintering, part of the conductive filler was still partially present within the ceramic matrix although some zirconium carbide was also formed., V.M. Sglavo and M. Biesuz kindly acknowledge the support from the Italian Ministry of University and Research (MIUR) within the programs PRIN2017 - 2017FCFYHK“DIRECTBIOPOWER” and Departments of Excellence 2018–2022 (DII-UNITN). M. Biesuz kindly acknowledge thesupport from MIUR within the programs PRIN2017 - 2017PMR932 “Nanostructured Porous Ceramics for Environmental and EnergyApplications”

Here were report a study of picene nano-cristalline thin films doped with pentacene molecules. The thin films were grown by supersonic molecular beam deposition with a doping concentration that ranges between less than one molecules of pentacene every 104 picene molecules up to about one molecule of pentacene every 102 of picene. Morphology and opto-electronic properties of the films were studied as a function of the concentration of dopants. The optical response of the picene films, characterized by absorption, steady-state and time-resolved photoluminescence measurements, changes dramatically after the doping with pentacene. An efficient energy transfer from the picene host matrix to the pentacene guest molecules was observed giving rise to an intense photoluminescence coming out from pentacene. This efficient mechanism opens the possibility to exploit applications where the excitonic states of the guest component, pentacene, are of major interest such as MASER. The observed mechanism could also serve as prototypical system for the study of the photophysics of host guest systems based on different phenacenes and acenes., Comment: 15 pages, 6 figures

Bilayer membranes for food packaging applications were prepared by depositing on polylactic acid (PLA) substrates pure cellulose nanofibers' (CNF) coatings and nanocomposite coatings made of CNF with dispersed TiO2 nanoparticles. The gas barrier properties of the bilayer membranes were studied by gas phase permeation technique using CO2, N2, D2, He and ambient air as test gases. Few micrometer thick pure and nanocomposite CNF coatings act as effective gas permeation barriers impeding the CO2, N2 and O2 transport and reducing the He and D2 transport rates by 3 orders of magnitude when compared with the PLA substrate. Gas transport through the coatings obeys the solution-diffusion mechanism: D2 permeation process shows activation energy values of 44 ± 6 kJ/mol and 40 ± 6 kJ/mol in the pure and nanocomposite CNF coating, respectively. The addition of the TiO2 nanoparticles reduces the penetrant diffusivity by increasing the tortuosity of the penetrant migration path but does not affect the gas barrier performances. UV–Vis spectroscopy analyses show that the optical transparency of the PLA support is slightly decreased by the CNF coating: at 600 nm the optical transmittance decreases, in fact, from 95% to 91%. TiO2 nanoparticles strongly absorb UV radiation and slightly reduce the PLA transparency in the optical range due to light scattering effects.

Graphene laminated (GL) coatings formed by stacked few layer graphene (FLG) nanocrystals were deposited on low-density polyethylene (PE) films by the mechanical rubbing technique. Molecular transport through the bilayer membrane was studied by the gas phase permeation technique by monitoring the CO2, N-2 and H-2(2) transport fluxes in transient conditions. The results evidenced that the transport exhibited anomalous character. The experimental data could be reproduced assuming that the penetrant concentration in the GL coating, c(int)(t), reached a saturation value c(s) following compressed exponential kinetics c(int)(t) = c(s)[1 - e(-(lambda relt)beta)]. The relaxation time tau(rel) = 1/lambda(rel) showed thermally activated behavior, and its value increased with the kinetic diameter of the penetrant molecules. The critical exponent beta = 1.5 +/- 0.1 for CO2 and N-2 and beta = 2.0 +/- 0.1 for H-2(2) did not change with temperature. Positron annihilation lifetime spectroscopy (PALS) analysis indicated that the average cross-section (h(g)) of the cavities in the GL coating exhibited comparable size to the kinetic diameter (sigma(k)) of the penetrant molecules. The results could be explained by assuming that the molecular infiltration in the GL structure occurred in nano-channels having distributed path lengths where the penetrant transport obeyed a configurational diffusion mechanism.

The interest towards aptamer-based surfaces in the field of bioaffinity assays is constantly growing. A crucial aspect is related to the ability of maintaining the high specificity of these molecules once immobilized on the surface. In this article we compare the immobilization of aptamers on a silanized silicon nitride surface as well as on a soft polymeric layer. An innovative immobilization approach, based on a copolymer, N-dimethylacrylamide-N-acryloyloxysuccinimide-3-(trimethoxysilyl)propylmethacrylate (DMA-NAS-MAPS) coating, able to crosslink itself to the substrate and to bind amino-modified biomolecules is proposed. Comparing this coating with a more classical functionalization process based on silane chemistry, we propose that the better results obtained on the polymeric layer are due to an increased binding efficiency of the aptamers bound to a soft material. The high specificity of immobilized DNA-aptamers is demonstrated using two sequences specific for thrombin detection and a non-sense sequence as negative control. The coating provides higher sensitivity compared to classical self-assembled silane coatings, probably due to a better mobility of bound aptamers. The aptamer immobilization on both surfaces was characterized and optimized using atomic force microscopy, X-ray photoelectron spectroscopy, contact angle and fluorescence microscopy. The comparison between the two different functionalizations highlights the better performances of the copolymer coating in terms of protein recognition, demonstrating thrombin detection down to 0.011 nM in buffer solution and 4.9 nM in complete human serum. Moreover, the localized immobilization of the aptameric sequences, utilized in this work, suggests the possibility of employing this platform also for multianalyte detection.

We have studied the kinetics of gas transport through films made of self-assembled cellulose nanofibrils (CNF) by a time-resolved mass spectroscopy technique. Few micrometers thick films deposited on polylactic acid (PLA) substrates act as impermeable barriers for CO2, O2, and N2 and reduce the 2H2 (deuterium) and He permeation flux by a factor of ∼103 with respect to the uncoated substrate. Penetrant transport is controlled by the solution-diffusion mechanism and the coating acts as a diffusive barrier. 2H2 and He diffusivity values are in the 10–10 and 10–9 cm2 s–1 range, respectively, and their migration occurs by thermally activated process with 39 ± 1 and 33 ± 2 kJ mol–1 activation energy. Positron annihilation lifetime spectroscopy analysis indicates that the diffusive path between the packed nanofibrils consists of elongated cavities with cross-sectional size ∼ 0.31 nm. Results evidence that the selective transport of the small size penetrants is due to sieving effects and that small penetrant tran...

Selective functionalization of the external/internal pore surface of porous silicon is of interest for the numerous potential applications of this material, in particular in pharmacology. With the aim of obtaining porous silicon platforms compatible with the aqueous environment and providing hydrophobic pores to load poorly water soluble molecules, we set-up a three step functionalization procedure consisting in two hydrosilylation reactions separated by the selective etching of the external surface. This procedure was applied both, to porous layers and porous microparticles. The characterization of the functionalized material by conventional techniques such as contact angle and FTIR showed a change of the properties of porous structures in line with the expected surface modifications. However, these techniques do not permit to clearly distinguish between internally and externally grafted functional groups. For this reason, an innovative procedure based on angle-resolved XPS was set-up and applied to differently functionalized pSi layers. By this technique, we obtained indications of prevalent grafting of hydrophilic moieties on the external surface and hydrophobic ones inside the pores.

A functionalization strategy, consisting of a silylation reaction by acrylic acid followed by diamine coupling, preserves and stabilizes the photoluminescence (PL) of porous silicon (pSi) microparticles suspended in ethanol. We found that under the condition of efficient amine coupling, besides the orange emission typical of the native pSi, an emission band in the blue region appears. The investigation of the interaction between pSi and diamine shows that diamine quenches and shifts the orange band meanwhile it induces an increase of the intensity of the blue one. PL lifetimes of the orange and blue bands are in the micro and nano second range, respectively. These values and their wavelength dependence clearly prove that the two bands have different origin: quantum confinement and nitrogen impurities introduced at silicon/silicon oxide interface, respectively. Thus, they can be used to discriminate between the pSi microparticles obtained by silylation, which expose carboxylic groups and the pSi microparticles after the diamine coupling, which bear amine functionalities at the surface. The increase in the stability of the PL emission of pSi in aqueous solution after functionalization, with quantum yields of the order of 1–2%, supports the use in biological systems of these brightly emitting, largely porous microparticles, bearing positive or negative surface charge.

In this study we investigated the fabrication of small hydrogel objects by the coordination-driven assembly of supramolecular rod-like crystallites of nanocellulose, using ionotropic gelation as a methodological approach and Ca2+ as a gelling agent. We proved that the gelation process is diffusion-mediated and fitting the equations modelling this process to the profile of the Ca2+ front, a Ca2+ diffusion coefficient in the incipient hydrogel of (4.5 ± 1.1) × 10−6 cm2 s−1 was calculated. At the steady-state a spatially homogeneous distribution of Ca2+-crosslinked sites in the hydrogel network was observed. External ionotropic gelation produced beads, wires or disks, while core–shell capsules were obtained by inverse ionotropic gelation. We demonstrated that equilibrium and dynamics of the distribution of Ca2+ offer the opportunity to design precisely the size and shape of these small hydrogel objects. In particular, the core size and the shell thickness of the capsules can be tailored under kinetic controlled conditions. The proposed approach, with supramolecular structures of the natural source as assembling components and the water-in-water fabrication process, is fast, simple, and requires only sustainable chemistry and is easily implementable in automatic microfluidic platforms.

International audience; We report the first synthesis of silicon nanocrystals embedded in a silicon nitride matrix through a direct pyrolysis of a preceramic polymer (perhydropolysilazane). Structural analysis carried out by XRD, XPS, Raman and TEM reveals the formation of silicon quantum dots and correlates the microstructures with the annealing temperature. The photoluminescence of the nanocomposites was investigated by both linear and nonlinear measurements. Furthermore we demonstrate an enhanced chemical resistance of the nitride matrix, compared to the typical oxide one, in both strongly acidic and basic environments. The proposed synthesis via polymer pyrolysis is a striking innovation potentially allowing a mass-scale production nitride embedded Si nanocrystals.

A quantum random number generator (QRNG) based on a silicon nanocrystals (Si-NCs) light emitting device (LED) coupled with a silicon single photon avalanche photodiode (Si-SPAD) is presented. A simple setup is used for the generation of random bits. The modeled approach assures a negligible bias on datasets of ∼100 Mbits length. The raw data pass all the statistical tests in the National Institute of Standards and Technology (NIST) suite without any post-processing operations. The bit-rate of 0.6 Mbps is achieved. The information-theoretically provable randomness extractor of Toeplitz-hashing function is applied to longer datasets (∼1 Gbits) to extract the randomness, to minimize the bias, and consequently pass all the NIST tests. Stabilizing the temperature, resetting the applied current to the LED, or a feedback system can also be used as parameter control solutions to generate good quality, long datasets of random numbers suitable for cryptographic applications.

Topology affects physical and biological properties of DNA and impacts fundamental cellular processes, such as gene expression, genome replication, chromosome structure and segregation. In all organisms DNA topology is carefully modulated and the supercoiling degree of defined genome regions may change according to physiological and environmental conditions. Elucidation of structural properties of DNA molecules with different topology may thus help to better understand genome functions. Whereas a number of structural studies have been published on highly negatively supercoiled DNA molecules, only preliminary observations of highly positively supercoiled are available, and a description of DNA structural properties over the full range of supercoiling degree is lacking. Atomic Force Microscopy (AFM) is a powerful tool to study DNA structure at single molecule level. We here report a comprehensive analysis by AFM of DNA plasmid molecules with defined supercoiling degree, covering the full spectrum of biologically relevant topologies, under different observation conditions. Our data, supported by statistical and biochemical analyses, revealed striking differences in the behavior of positive and negative plasmid molecules.

Matrix Assisted Laser Desorption Ionization (MALDI) is a soft ionization method with widespread analytical applications. One of its limits is the spurious signal in the low mass region, due to the required use of matrices to desorb and ionize the analytes. The possibility to avoid their use will ease both sample preparation and mass spectrum interpretation because the low mass region will not be crowded by peaks of the matrix. In recent years, nanostructured materials have been proposed as matrix-free substrates, but their use is limited to specific combination of nanostructures and analytes, while no general matrix-free approach has yet been demonstrated. Here we propose a radically new type of transducer and we demonstrate that fluorosilanized bulk surfaces achieve similar detection limit of nanostructured substrates. The results of our work suggest that desorption/ionization (D/I) is a purely interfacial effect, with negligible contribution from the chemical nature of the underlying substrate, provided that the substrate contains fluorine species, is an electrical conductor and a good UV absorber.

Sol-gel transition of carboxylated cellulose nanocrystals has been investigated using rheology, SAXS, NMR and optical spectroscopies to unveil the distinctive roles of ultrasound treatments and addition of various cations. Besides cellulose fiber fragmentation, sonication treatment induces fast gelling of the solution. The gelation is independent of the addition of cations, while the final rheological properties are highly influenced by the type, concentration and sequence of the operations since the cations must be added prior to sonication to produce stiff gels. The gel elastic modulus was found to increase proportionally to the ionic charge rather than the cationic size. In cases where ions were added after sonication, SAXS analysis of the Na+ hydrogel and Ca2+ hydrogel indicated the presence of structurally ordered domains in which water is confined, and 1H-NMR investigation showed the dynamics of water exchange within the hydrogels. Conversely, separated phases containing essentially free water were characteristic of the hydrogels obtained by sonication after Ca2+ addition, confirming that this ion induces irreversible fiber aggregation. The rheological properties of the hydrogels depend on the duration of the ultrasound treatments, enabling the design of programmed materials with tailored energy dissipation response.

In this article we describe a reliable etching method to fabricate porous silicon free-standing membranes (FSMs) based on a self detachment of the porous layer in moderately doped n-type silicon substrates. We found that stable growth of smooth and straight pores is restricted to a narrow range of etching conditions and, unlike p-type substrates, the lift-off of the membrane is a self-limited process that does not require a large burst of current. The detachment of the porous membrane is independent of the structure of the already porosified layer, meaning that the average pore diameter can be tuned from nano to macro size within the same membrane. We also demonstrate that, despite their limited thickness, FSMs are quite robust and can sustained further processing. Thus, the etching receipt we are proposing here extends the range of sensors and filters that can be fabricated using porous silicon technology.

Exosomes, which are membranous nanovesicles, are actively released by cells and have been attributed to roles in cell-cell communication, cancer metastasis, and early disease diagnostics. The small size (30–100 nm) along with low refractive index contrast of exosomes makes direct characterization and phenotypical classification very difficult. In this work we present a method based on Single Particle Interferometric Reflectance Imaging Sensor (SP-IRIS) that allows multiplexed phenotyping and digital counting of various populations of individual exosomes (>50 nm) captured on a microarray-based solid phase chip. We demonstrate these characterization concepts using purified exosomes from a HEK 293 cell culture. As a demonstration of clinical utility, we characterize exosomes directly from human cerebrospinal fluid (hCSF). Our interferometric imaging method could capture, from a very small hCSF volume (20 uL), nanoparticles that have a size compatible with exosomes, using antibodies directed against tetraspanins. With this unprecedented capability, we foresee revolutionary implications in the clinical field with improvements in diagnosis and stratification of patients affected by different disorders.

Flexible optoelectronics has emerged as an outstanding platform to pave the road toward vanguard technology advancements. As compared to conventional rigid substrates, a flexible technology enables mechanical deformation while maintaining stable performance. The advantages include not only the development to novel applications, but also the implementation of a wearable technology directly in contact with a curved surface. Here the monolithic integration of a perovskite‐based optical waveguide amplifier together with a photodetector on a nanocellulose substrate is shown to demonstrate the feasibility of a stretchable signal manipulation and receptor system fabricated on a biodegradable material. An integrated optical amplifier–photodetector is developed in which the photocurrent is exploited that is generated in the organic–inorganic lead halide perovskite under an applied bias. Such photocurrent does not minimally perturb the amplifier operation and is used to monitor the light signal propagating along the waveguide, opening a broad range of applications for example to regulate the operation temperature.

Here we report an investigation of the growth of picene by supersonic molecular beam deposition on thermal silicon oxide and on a self-assembled monolayer of hexamethyldisiloxane (HMDS). In both cases film morphology shows a structure with very sharp island edges and well-separated islands which size and height depend on the deposition conditions. Picene films growth on bare silicon covered with hydrophobic HDMS shows islands characterized by large regular crystallites of several micrometers; on the other hand, films growth on silicon oxide shows smaller and thicker islands. We analyzed the details of the growth model and describe it as a balancing mechanism involving the weak interaction between molecules and surface and the strong picene-picene interaction that leads to a different Schwoebel-Ehrlich barrier in the first layer with respect to the successive one. Finally, we study the charge transport properties of these films by fabricating field-effect transistors devices in both top and bottom contact configuration. We notice that substrate influences the electrical properties of the device and we obtained a maximum mobility value of 1.2 cm2 V-1 s-1 measured on top contact devices in air. © 2012 American Chemical Society.

Porous materials are ideal hosts to fabricate high sensitivity devices. Their large specific area and the possibility to modify the type and the strength of the matrix–analyte interactions allow the realization of sensors with finely tailored characteristics. In this article, we investigate how mass transport across the nanoporous structure influences the response due to the non-specific signal by comparing flow-through versus flow-over geometries. We observed a systematic overestimation of the sensitivity for porous substrate devices made of closed-ended pores compared with open-ended pore ones. Our analysis shows that such an effect is due to (unbound) analytes or contaminants that remain trapped within the pores and are not removed by rinsing of the sample. This result was verified by measuring similar samples in both flow through and flow over configurations, as well as their residual response after blockage of all their active sites. We also notice that sensors based on free-standing membranes show similar results independent of the fact that mass transport is induced by either an external pressure source or simply by Brownian motions.

The effect of surface roughness on the optical absorption of a porous material is numerically investigated. We performed a comparative study among different porous geometries and we demonstrate that the presence of the roughness significantly increases the optical absorption of light. This effect is optimized by using a proper matching layer that minimizes losses and maximizes absorption. Enhanced absorption is achieved over a broad range of wavelengths in these simple bilayered structures. The results of this work can be used to design more effective light trapping devices, e.g., third-generation photovoltaic backreflector exploiting the bandgap incident radiation.

We present low temperature transfer bonding of porous silicon membranes to polymeric microfluidic devices, using neither adhesives nor bond surface treatment. The transfer is enabled by a novel dual cure ternary monomer system containing thiolene and epoxy. The ability of the epoxy to react with almost any dry substrate provides a very versatile fabrication method. We characterize the two stage curing mechanism, describe the device fabrication, and evaluate the bond strength.

Silicon photonics has produced the first all-optical components intergrated into systems available already on the market. Nanosilicon, where low dimensional silicon allows new phenomena and devices, is a way to expand the

Integrated silicon photonics is nowadays a mature technology and it is considered one of the most likely solution to overcome crucial limits of electronics systems. In fact photonics will enables the realization of integrated devices with greater data transmission capacity, reduced power consumption and smaller latency[1].

Here, we report on the design, fabrication and characterization of single-channel (SC-) and dual-channel (DC-) side-coupled integrated spaced sequences of optical resonators (SCISSOR) with a finite number (eight) of microring resonators using submicron silicon photonic wires on a silicon-on-insulator (SOI) wafer. We present results on the observation of multiple resonances in the through and the drop port signals of DC-SCISSOR. These result from the coupled resonator induced transparency (CRIT) which appears when the resonator band (RB) and the Bragg band (BB) are nearly coincident. We also observe the formation of high-Q (> 23000) quasi-localized modes in the RB of the drop transmission which appear when the RB and BB are well separated from each other. These multiple resonances and quasi-localized modes are induced by nanometer-scale structural disorders in the dimension of one or more rings. Finally, we demonstrate the tunability of RB (and BB) and localized modes in the DC-SCISSOR by thermo-optical or free-carrier refraction.

A novel wavelength routing device for optical on-chip network applications is presented. It is based on the constructive and destructive interferences that occur when two side-coupled integrated spaced sequences of resonators (SCISSORs) are coupled in parallel to a single common waveguide. Its potential application for coarse wavelength division multiplexing, i.e., band routing functionalities, and its robustness against fabrication tolerances and signal imbalances are analyzed. Design, simulation, fabrication, and experimental characterizations are described. We compare measurements of the fabricated device with simulations for the ideal and the actual device, where random variations in the geometrical parameters inherent in the fabrication process are considered. This allows demonstrating the concept of interferometric SCISSOR routing and to discuss the limits and advantages of coupled resonator-based design for routing.

The design of materials capable of mechanical responses to physical and chemical stimuli represents one of the most exciting and challenging areas of scientific research because of the huge number of their potential applications. This article is focused on the molecular events occurring in thin films of carboxylated nanocellulose fibers, which are capable of converting water gradients into mechanical movements at the macroscopic scale. The analysis of the mechano-actuation, and of the conditions to obtain it, shows that the film movement is fast and reproducible, the gradient intensity is transduced into rate of displacement, and the response is observed at vapor pressures as low as 1.2 mm Hg. The actuation mechanism is associated to an efficient and reversible water sorption process by the hydrophilic nanocellulose fibers at the film interface. Conversely, water desorption is slow and follows a kinetic behavior supporting the presence of two binding sites for water molecules. The adsorbed water induces swelling of the surface nanocellulose layers and local structural rearrangement, however transitions between ordered and random coil conformations are not observed. The understanding of the actuation mechanisms of nanocellulose offers exciting opportunities to design macroscopic structures responding to chemical gradients by the assembly of simple molecular components.

We present two transfer bonding schemes for incorporating fragile nanoporous inorganic membranes into microdevices. Such membranes are finding increasing use in microfluidics, due to their precisely controllable nanostructure. Both schemes rely on a novel dual-cure dry adhesive bonding method, enabled by a new polymer formulation: OSTE(+), which can form bonds at room temperature. OSTE(+) is a novel dual-cure ternary monomer system containing epoxy. After the first cure, the OSTE(+) is soft and suitable for bonding, while during the second cure it stiffens and obtains a Young's modulus of 1.2 GPa. The ability of the epoxy to react with almost any dry surface provides a very versatile fabrication method. We demonstrate the transfer bonding of porous silicon and porous alumina membranes to polymeric microfluidic chips molded into OSTE(+), and of porous alumina membranes to microstructured silicon wafers, by using the OSTE(+) as a thin bonding layer. We discuss the OSTE(+) dual-cure mechanism, describe the device fabrication and evaluate the bond strength and membrane flow properties after bonding. The membranes bonded to OSTE(+) chips delaminate at 520 kPa, and the membranes bonded to silicon delaminate at 750 kPa, well above typical maximum pressures applied to microfluidic circuits. Furthermore, no change in the membrane flow resistance was observed after bonding. QC 20130125 Positive

Silicon photonics is the emerging optical interconnect technology where integrated nanophotonic components allow reaching high device density and improved optical functional- ities. One key component is the optical microresonator. A particular kind of microresonator is the racetrack resonator where straight waveguide sections are used to achieve a large value of the coupling coefficient with a bus waveguide for any light polarization state. It is our aim to study the performances of racetrack resonators fabricated on silicon on insulator via CMOS pro- cessing. We experimentally investigated different multiple resonator designs where box-shaped filter characteristic, Vernier effect, and coupled resonator induced transparency effects are ob- tained. We demonstrate that racetrack resonators are instrumental to several different functions in nanophotonics and that the actual lithographic process is fully capable of building these

The microring resonator is a ubiquitous building block of optical integrated circuits. Owing to its unique non-linear properties, it appears well-suited as a node in the realization of photonic networks, such as spiking neural networks. However, experimental investigation requires complex setups, incurring considerable device fabrication times and costs. Inherent physical constraints limit the ranges of the parameters determining the timescales and strengths of the non-linear behaviors. Moreover, on-the-fly changes to these parameters and node couplings are not easily realizable. On the other hand, numerical simulations are computationally heavy, particularly for large networks, and do not entirely replace measurement on a physical apparatus. To mitigate this problem, we introduce and realize an analog electronic emulator that implements dynamics, attempting to reproduce the self-pulsing phenomenon in an optical microresonator. It can be readily constructed with off-the-shelf components, and is well-suited for building complex networks. The circuit is explicitly based on a mathematical model of the microresonator, subject to some approximations, parameter adjustments and rescalings. Initial results comparing experimental data from the emulator and a representative silicon photonic device plus numerical simulations suggest a satisfactory level of agreement in the temporal dynamics and response to parametric sweeps when scaled for the different response times. This work exemplifies the relevance of explicitly establishing correspondences between physical systems having widely different features but governed by similar dynamics.

Thermal transport in nano-Porous material has drawn the attention of several research groups during the last decade due to the ability of such structures to tailor efficiently the thermal properties of materials and more specifically to lower drastically the thermal conductivity of semiconductors. The present chapter recalls the basics of thermal transport in porous media from different standpoints. After a short introduction and review of the literature, analytic models that characterize heat propagation in porous media are given. Their limitations, especially in what concerns heat carriers scattering with pores when characteristic sizes become very small is pointed out and alternatives are suggested. In a second time, Monte Carlo modeling techniques, which are well designed for mesoscopic length-scales, are introduced and their use for thermal conductivity appraisal of nano-porous media is discussed. Improvement of such technique to reduce computation time and to model thin films with high porosity is then exposed with Effective Monte Carlo model. Simulation results for silicon and germanium support this part. The last section of the chapter is devoted to Molecular Dynamic (MD) modeling of nano-porous structures. Again, practical details on Equilibrium MD are proposed with a specific attention paid to crystalline and amorphous phases modeling. Then simulation results for various kinds of a-Si and c-Si nano-porous structures are discussed before concluding on all these methods and models.