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The response time of state-of-the-art humidity sensors is ≈8 s. A faster tracking of humidity change is especially required for health care devices. This research is focused on the direct nanostructuring of a humidity-sensitive polymer thin film and it is combined with an optical read-out method. The goal is to improve the response time by changing the surface-to-volume ratio of the thin film and to test a different measurement method compared to state-of-the-art sensors. Large and homogeneous nanostructured areas are fabricated by nanoimprint lithography on poly(2-hydroxyethyl methacrylate) thin films. Those thin films are made by initiated chemical vapor deposition (iCVD). To the author's knowledge, this is the first time nanoimprint lithography is applied on iCVD polymer thin films. With the imprinting process, a diffraction grating is developed in the visible wavelength regime. The optical and physicochemical behavior of the nanostructures is modeled with multi-physic simulations. After successful modeling and fabrication a first proof of concept shows that humidity dependency by using an optical detection of the first diffraction order peak is observable. The response time of the structured thin film results to be at least three times faster compared to commercial sensors.

On-surface chemistry holds the potential for ultimate miniaturization of functional devices. Porphyrins are promising building-blocks in exploring advanced nanoarchitecture concepts. More stable molecular materials of practical interest with improved charge transfer properties can be achieved by covalently interconnecting molecular units. On-surface synthesis allows to construct extended covalent nanostructures at interfaces not conventionally available. Here, we address the synthesis and properties of covalent molecular network composed of interconnected constituents derived from halogenated nickel tetraphenylporphyrin on Au(111). We report that the π-extended two-dimensional material exhibits dispersive electronic features. Concomitantly, the functional Ni cores retain the same single-active site character of their single-molecule counterparts. This opens new pathways when exploiting the high robustness of transition metal cores provided by bottom-up constructed covalent nanomeshes.

Since their first appearance, organic-inorganic perovskite absorbers have been capturing the attention of the scientific community. While high efficiency devices highlight the importance of band level alignment, very little is known on the origin of the strong n-doping character observed in the perovskite. Here, by means of a highly accurate photoemission study, we shed light on the energy alignment in perovskite-based devices. Our results suggest that the interaction with the substrate may be the driver for the observed doping in the perovskite samples.

The aim of the current work is to improve the response time of an optical readout based humidity sensor. Therefore, we present the application of nanoimprint lithography (NIL) on thin films which are deposited by initiated chemical vapor deposition (iCVD). Hydrogels are polymeric networks with the ability to swell after certain physical conditions change, which makes them very useful as sensing layers for optical devices. In the first step we used iCVD to deposit a humidity responsive hydrogel (here: pHEMA) as a planar thin film on sapphire substrates. To increase the effective surface area, we tried for the first time NIL on our hydrogel thin films with promising results: First, characterization with a SEM showed that NIL allows the design of large homogeneous areas of nanostructures without damaging the sensitive hydrogel thin film and having a great stability at ambient conditions. Second, NIL offers the benefit to build different geometries and sizes of nanostructures based on the requested application. For our first test we selected a simple line array structure, combined with an optical detection method as sensor principle. By choosing a specific structure to wavelength ratio the imprinted nanostructures act as a diffraction grating enabling a fast response time by increasing the effective sensing area. Since in our application the hydrogel works as the sensing element, we observed a humidity dependence behavior by measuring the intensity of the first order diffraction peak. Finally, the response time was a lot faster by using optical detection methods than commercial humidity sensors.

Nanoscience and nanotechnology are broad domains of research and innovation that represent a major fi eld of activity at global level. This originates from the outstanding demonstrations obtained in the last two decades of the possibility to control the organization of matter at the scale of few atoms and molecules, to address their properties and to obtain functional systems with potential exploitation in the fields of health, environment, energy and communication. Research in nanoscience requires direct sensitivity to the atomic scale and to the fundamental time scale of the processes ruling the assembly of matter and the interactions with light, electric current, and molecules at all levels of complexity, from the gases of the atmosphere to proteins and DNA. Nanoscience therefore necessitates special research infrastructures like “atomically clean environments” for the synthesis and the assembling of nanosystems on the one hand, and advanced radiation sources for the direct analysis of their properties (Large Scale Facilities for fine analysis of matter, LSFs) and for controlling the functionalities at the relevant space and time scale of the fundamental processes on the other hand. Both these infrastructures, which require substantial investment in terms of human and financial resources, are most often not co-located and not operated in close synergy. While the European offer of LSFs is adequate, the availability of open access nanoscience centres is overall undersized, and the link to LSF is weak. This is a severe limitation for the optimal development of nanoscience and the ensuing nanotechnologies, as well as a limiting factor for a scientifi c return from the LSFs. State of the art synthesis and characterization laboratories lack the direct use of numerical modelling, fine analysis, in-situ and in-operando experiments. Advanced beamlines on synchrotron radiation sources, free electron lasers and neutron sources generally lack adequate synthesis and sample preparation and delivery tools, or atomic resolution microscopy. Numerical simulations are most often performed on model systems and are not on-line with synthesis and experimental work. The Nanoscience Foundries & Fine Analysis project (NFFA) addresses the integration of all these competences and methods by setting up a European Distributed Research Infrastructure that will co-locate 3-6 Nanoscience Centres with LSFs and thus shall offer a unique environment for advanced research by providing open access to European and international scientists. NFFA intends to play a key role in the construction of the European Research Area by creating a unique environment for the support of leading research by users from academy and institutes, by offering advanced training to young researchers and engineers and by providing an effective support to innovation projects by diverse stakeholders. This booklet summarizes the outcomes of the NFFA Design Study and outlines the strategic needs and roadmap for the implementation of the NFFA Research Infrastructure.

Since their first appearance, organic-inorganic perovskite absorbers have been capturing the attention of the scientific community. While high efficiency devices highlight the importance of band level alignment, very little is known on the origin of the strong n-doping character observed in the perovskite. Here, by means of a highly accurate photoemission study, we shed light on the energy alignment in perovskite-based devices. Our results suggest that the interaction with the substrate may be the driver for the observed doping in the perovskite samples.

Guiding of the phase separation of a block copolymer (BCP) by an electric field perpendicular to the substrate is investigated in order to obtain vertical structures that can provide a mask for subsequent etching. Because of practical aspects, the substrate is bare Si without any neutral brush and the process time is limited to 1 h. A polystyrene-block polymethylmethacrylate lamellar material is employed in the study. For a unique guiding of the lamellar phase, an ordering mechanism orthogonal to the electric field is introduced by the interaction with the stamp in a thermal nanoimprint process. The naturally low surface energy of the stamp shall induce the formation of lamellae along the sidewalls of linear cavities. In order to fully utilize these two ordering mechanisms, the stamp sidewalls and the electric field, the imprint process is conducted in such a way that no residual layer remains below the stamp structures and the whole BCP is accumulated inside the cavities which are just partly filled. The electrically-assisted imprint process is studied analytically, considering the capacitive effects due to the local electric field in the cavity and in particular in the BCP. In addition, a numerical simulation is performed for the actual experimental conditions to compute the electric vector field in the BCP. In this way, an extensive understanding of the situation is gained which is the basis for choosing optimal experimental conditions for electrically-assisted thermal nanoimprint. Furthermore, the ambiguity of the electric field in a thermal nanoimprint process with partly filled cavities is addressed. The field shall induce vertical phase separation but, due to instabilities, it also may induce capillary bridges that represent replication defects. An improvement of the vertical phase separation by applying an electric field as high as 25 V/mu m could be identified under specific experimental conditions. However, the guiding effect within the cavities and thus the long-range order of the lamellae remained limited. This may be due to a field strength too low in the BCP; in the present configuration, higher field strengths are prohibited by an electrical breakthrough. Published by the AVS.

Although it is well recognized that cell-matrix interactions are based on both molecular and geometrical characteristics, the relationship between specific cell types and the three-dimensional morphology of the surface to which they are attached is poorly understood. This is particularly true for glomerular podocytes - the gatekeepers of glomerular filtration - which completely enwrap the glomerular basement membrane with their primary and secondary ramifications. Nanotechnologies produce biocompatible materials which offer the possibility to build substrates which differ only by topology in order to mimic the spatial organization of diverse basement membranes. With this in mind, we produced and utilized rough and porous surfaces obtained from silicon to analyze the behavior of two diverse ramified cells: glomerular podocytes and a neuronal cell line used as a control. Proper differentiation and development of ramifications of both cell types was largely influenced by topographical characteristics. Confirming previous data, the neuronal cell line acquired features of maturation on rough nanosurfaces. In contrast, podocytes developed and matured preferentially on nanoporous surfaces provided with grooves, as shown by the organization of the actin cytoskeleton stress fibers and the proper development of vinculin-positive focal adhesions. On the basis of these findings, we suggest that in vitro studies regarding podocyte attachment to the glomerular basement membrane should take into account the geometrical properties of the surface on which the tests are conducted because physiological cellular activity depends on the three-dimensional microenvironment.

Here we present a new bonding protocol for SU-8 negative tone photoresist that exploits the chemical modifications induced in the resin by exposure to 254 nm (UVC) light. Fourier Transform Infrared microspectroscopy (mu-FTIR) was used to carry out a thorough study on the chemical processes and modifications occurring within the epoxy resin by exposure to 365 nm and 254 nm light. In particular, we established that UVC light promotes the opening of the epoxy rings bypassing the post-exposure bake. The possibility to promote a further activation of the resin, already patterned with standard UV lithography, was exploited to produce closed microfluidic devices. Specifically, we were able to fabricate fluidic chips, characterized by broadband transparency from mid-IR to UV and long term stability in continuous flow conditions. CaF2 was used as substrate, coated by sputtering with a nanometric silicon film, in order to make surface properties of this material more suitable for standard fabrication processes with respect to the original substrate. The fabricated microfluidic chips were used to study by mu-FTIR the biochemical response of live breast cancer MCF-7 cells to osmotic stress and their subsequent lysis induced by the injection of deionized water in the device. mu-FTIR analyses detected fast changes in protein, lipid and nucleic acid content as well as cytosol acidification.

This paper is focused on the understanding of the effect of the nanoimprint lithography process on the elastic modulus of thin, thermoplastic films. In particular, we present the comparison between the standard and an ultrafast thermal NIL technology as well as the way both processes affect the top surface of poly(methyl methacrylate) (PMMA). The PeakForce QNMź (Quantitative Nanomechanical Property Mapping) scanning probe technique was used to determine the Young's modulus of PMMA by comparison with a polystyrene standard. We demonstrate that imprinted PMMA, regardless of the used method, shows a 9-fold increase of Young's modulus compared to non-imprinted PMMA at least in the top 3-5nm thick surface layer. This important finding proves that the ultrafast process with much higher temperatures, but also with much shorter process times, leads to elastic surface properties that are comparable to those of PMMA imprinted with the standard process. We have confirmed that annealing alone does not significantly influence the Young's modulus. Display Omitted PeakForce QNM analysis of Young's modulus of imprinted PMMA by thermal and Pulsed NILPMMA undergoes 9-fold increase of Young's modulus upon imprinting.Thermal NIL and Pulsed-NIL affect similarly the mechanical properties of PMMA.

In this contribution we present the first example of a microfiuidic chip based on BaF2 for Infrared Microspectroscopy (IBMS) of living cells. The advantage in using barium fluoride as platform relies on its high IR transparency, especially in the spectral region below 1300 cm(-1), where the absorption bands of nucleic acids and carbohydrates are located. Barium fluoride is slightly soluble in water (0.12 g/100 g water) and it is potentially harmful for living cells. To overcome these problems, here we exploit an approach whose feasibility has been demonstrated previously on CaF2: the surface modification obtained by sputtering a thin Si layer on the surface. The Surface Modified Microfluidic Devices (SM-MD) hence obtained not only solve the BaF2 drawbacks, but also provide a silicon-like substrate fully compatible with standard micro-fabrication processes. These potentialities are here further explored in the direction of chemical or topographical nano-patterning of the silicon-like surface. The silicon thin layer was structured in the shape of 300 nm wide grooves (500 nm pitch) with a thickness of 35 nm by using standard NIL and etching processes; chemical patterning was achieved by exploiting silane chemistry. Finally, we tested the performances of these devices at SISSI beamline@Elettra, collecting IR spectra of single MDA-MB-231 living cells maintained either in physiological solution or complete medium. A comparison of the spectra of a single cell obtained in BaF2 and CaF2 MDs is reported. (C) 2013 Elsevier B.V. All rights reserved.

Presently, no resist material has suitable properties to satisfy simultaneously all requirements on lateral resolution and plasma etching resistance for pattern transfer of high aspect ratio nano-structures. Herein, a recent innovative alumina spin-on material for use as both positive and negative high resolution resist for electron beam lithography (EBL) is presented. This system turns into an almost completely inorganic alumina system when exposed to the electron beam, showing exceptional selectivity (100:1), compared to even the most robust polymeric resist, when used as mask for dry etching of silicon in fluorinated plasmas, obviating the need for a hardmask layer deposition. A full characterization of the resist selective removal under different processing conditions, such as electrons acceleration voltage and post-exposure bake temperature and time, is presented. Owing to the high selectivity and high resolution, silicon nano-structures of size down to 11 nm and high aspect ratio (up to 20) have been obtained for the first time in a one-step process.

We report the nanopatterning of the methylammonium lead iodide (MAPbI3) perovskite, a polycrystalline hybrid organic-inorganic semiconductor with very promising perspectives for photovoltaic and optoelectronic applications. Nanopatterning of MAI is obtained via Pulsed-NIL technology, an ultrafast version of the thermal nanoimprint lithography (NIL) based on stamps with integrated heaters. By Pulsed-NIL we were able to replicate onto the hybrid perovskite structures with details at the sub-100nm scale, in spite of its crystalline nature. This work shows a new possibility for the exploitation of organo-metal halide perovskites in optoelectronic devices with more complex architectures than just planar films. Display Omitted Methylammonium lead iodide thin film nanoimprinting approach is proposed.V-groove nanostructures are transferred to the photoactive material via Pulsed-NIL.The technique allows to perform the step in less than 1s.The preliminary trials show the possibility to scale up the process.

In this paper, we investigate conjugated polymer layers structured by nanoimprint lithography toward their suitability for the fabrication of nanostructured polymer/metal sulfide hybrid solar cells. Consequently, we first study the thermal stability of the nanoimprinted conjugated polymer layers by means of scanning electron microscopy and grazing incidence small-angle X-ray scattering, which reveals a reasonable thermal stability up to 145 degrees C and sufficient robustness against the solvent mixture used in the subsequent fabrication process. In the second part, we demonstrate the preparation of nanostructured polymer/copper indium sulfide hybrid solar cells via the infiltration and thermal decomposition of a mixture of copper and indium xanthates. Although this step needs temperatures of more than 160 degrees C, the nanostructures are retained in the final polymer/copper indium sulfide layers. The nanostructured solar cells show significantly improved power conversion efficiencies compared to similarly prepared flat bilayer devices, which is based on a distinct improvement of the short circuit current in the nanostructured solar cells.

Catalyst nanoparticles are required in most established synthetic routes for the growth of carbon nano-tubes (CNTs) and semiconductor nanowires (NWs). A simple and widespread method to coat a substrate with metal nanoparticles is based on the dewetting of a thin metal film, often induced by a process of thermal annealing, and resulting in the formation of fine droplets. However, the control of the sole thermodynamic parameters affecting the dewetting results in a rather broad size distribution and random positioning of the catalyst. Efforts aiming at a better control of size and position of the catalytic seeds by top-down and bottom-up patterning techniques are well documented. However, patterning the catalyst may be a useless process step if, once approaching the temperatures at which the growth of nanowires and CNTs is catalyzed, nanoparticles become mobile on the substrates, displacing from their position and altering the initial size distribution due to coalescence. Moving from this observation, we propose a simple and general method to prevent the diffusion of the catalyst during annealing steps or the initial stage of the synthesis of NWs and CNTs. Its principle consists of confining the catalyst nanoparticles on top of vertical columnar structures. This can be achieved by etching the substrate all around the nanoparticles by dry anisotropic etching using the nanoparticles themselves as etch masks. Nanopartides thus sitting on top of nanopillars result effectively confined, even at temperature at which they are found highly mobile on flat substrates of the same material, due to surface tension effects. Experimentally, we demonstrate this principle with iron nanodots obtained on silicon by lift-off starting from a P(MMA-b-S) diblock-copolymer template. The iron nanodots isolated on top of columnar nanostructures, were found to be stable at 600 degrees C, temperature suitable for the growth of CNTs. (C) 2013 Elsevier B.V. All rights reserved.

Nanoelectrode arrays (NEAs) are increasingly applied for a variety of electroanalytical applications; however, very few studies dealt with the use of NEAs as an electrochemical generator of electrogenerated chemiluminescence (ECL). In the present study, arrays of nanodisc and nanoband electrodes with different dimensions and inter-electrode distances were fabricated by e-beam lithography on a polycarbonate layer deposited on boron-doped diamond (BDD) substrates. In particular, NEAs with 16 different geometries were fabricated on the same BDD sample substrate obtaining a multiple nanoelectrode and ultramicroelectrode array platform (MNEAP). After electrochemical and morphological characterization, the MNEAP was used to capture simultaneously with a single image the characteristic behaviour of ECL emission from all the 16 arrays. Experiments were performed using Ru(bpy)(3) (2+) as the ECL luminophore and tri-n-propylamine (TPrA) as the co-reactant. With a relatively limited number of experiments, such an imaging procedure allowed to study the role that geometrical and mechanistic parameters play on ECL generation at NEAs. In particular, at high concentrations of TPrA, well-separated individual ECL spots or bands revealed an ECL signal which forms a pattern matching the nanofabricated structure. The analysis of the imaging data indicated that the thickness of the ECL-emitting zone at each nanoelectrode scales inversely with the co-reactant concentration, while significantly stronger ECL signals were detected for NEAs operating under overlap conditions. Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/3566]

Site-controlled epitaxial growth of InAs quantum dots on GaAs substrates patterned with periodic nanohole arrays relies on the deterministic nucleation of dots into the holes. In the ideal situation, each hole should be occupied exactly by one single dot, with no nucleation onto planar areas. However, the single-dot occupancy per hole is often made difficult by the fact that lithographically-defined holes are generally much larger than the dots, thus providing several nucleation sites per hole. In addition, deposition of a thin GaAs buffer before the dots tends to further widen the holes in the [110] direction. We have explored a method of native surface oxide removal by using indium beams, which effectively prevents hole elongation along [110] and greatly helps single-dot occupancy per hole. Furthermore, as compared to Ga-assisted deoxidation, In-assisted deoxidation is efficient in completely removing surface contaminants, and any excess In can be easily re-desorbed thermally, thus leaving a clean, smooth GaAs surface. Low temperature photoluminescence showed that inhomogeneous broadening is substantially reduced for QDs grown on In-deoxidized patterns, with respect to planar self-assembled dots.

We have successfully grown regular arrays of InAs/GaAs quantum dots on patterned Si substrates. Thanks to the capability of nanoimprint lithography, we were able to obtain uniform patterns extended over some cm(2) areas, with periods of 300 nm. Ex-situ and in-situ treatments of the surface allowed us to completely remove any residual oxides prior to growth without the use of hydrogen beams, at temperatures compatible with standard III-V molecular beam epitaxy. The growth protocol was optimized in order to obtain a perfect selectivity of InAs/GaAs nanostructures in the holes, without any deposition on the planar areas. (C) 2015 Elsevier B.V. All rights reserved.

Natively porous hybrid organic-inorganic sol-gel systems have been engineered to be used as functional positive photoresists, aimed to the realization of microsensors in a single-step process. Interesting results have been obtained combing three main sol-gel system features: the direct pattern-ability through X-ray lithography, being processable without the addition of a photocatalyst; the functionalizability, properly designing the organic component of the hybrid network or incorporating active species; the open micro or mesoporosity, tailored by the synthesis process and precursor choice. The photoprocessable porous films have been synthesized starting from a Bridged Polysilsesquioxane (BPS) precursor, 1,4-bis(triethoxysilyl)benzene. The correlation between chemical properties of the solgel material and its patternability is described in detail. X-ray exposure leads to a progressive alkyl and aromatic compound elimination and promotes inorganic condensation in the system, allowing the selective dissolution of irradiated cross-linked films in suitable etchants. Patterns of final resolution lower than 100 nm have been realized on BPS-based films synthesized in acid conditions, a procedure that allows to take advantage of a straightforward embedding protocol for active species in the sol-gel matrix. The BPS-based system has been doped with a covalently linked quinolinium dye, obtaining thin sensing films patternable by X-ray lithography. A feasibility test for the fabrication of optical microdevices, where fluorescence properties are obtained directly on the patterned coatings, has been provided. (C) 2010 Elsevier B.V. All rights reserved.

A nanofabrication process for high resolution X-ray optics and X-ray lithography masks was developed. The process is based on the plasma etching of a sacrificial hard inorganic interlayer (Si, Si(3)N(4), SiO(x) or HSQ) used for pattern transfer and aspect ratio amplification. The structures are first defined on a top thin metal film by electron beam lithography and lift-off; a thin nickel layer at the bottom of the hard interlayer is used as etch stop. A base plating (Cr/Au) under the nickel serves as seed layer for the electroplating of an X-ray absorber or phase shifting material. The fabrication is completed by the stripping of the hard template by wet or dry etching. Compared to methods based on analogous process schemes, in which the aspect ratio of nanostructures is instead amplified by pattern transfer into a sacrificial polymer interlayer by oxygen plasma, the investigated method is advantageous for the higher mechanical stability of the nanostructured hard templates with respect to the polymer ones, thus enabling the realization of higher aspect ratio features. (C) 2011 Elsevier B.V. All rights reserved.

Hybrid sol-gel materials are suitable dielectric materials for a range of optical applications, due to the versatility by which their optical and mechanical properties can be adjusted and the easy patterning by various lithographic techniques. We report on the synthesis of engineered epoxy based hybrid organic-inorganic sol-gel materials and on their lithographic processing, specifically applied to the fabrication of microlens arrays. The investigated sol-gel systems exhibit enhanced transparency in the near UV region with respect to most commercial thermoplastic polymers and sol-gel materials, used in embossing and nanoimprinting technology; in addition, they offer a better shape stability and superior mechanical properties, such as higher elastic modulus and hardness, improving the perspectives of the introduction of microstructured and nanostructured surfaces in applications where resistance to environmental mechanical-chemical degradation mechanisms is highly desirable, in particular for outdoor applications.

Engineering of the cellular microenvironment has become an attractive strategy to guide cellular activities such as spreading, motility, proliferation and differentiation. From a technological perspective, the physical crosstalk between a cell and its surrounding represents a design parameter that may be modulated to achieve desired osseointegration in orthopedic and dental implants. In this study we use a surface engineering approach to tap into the interaction between the cell and its surroundings in order to modulate osteogenic adhesion-dependent differentiation and bone tissue formation. The effectiveness of this approach was studied by observing the in vitro cellular behavior of human osteoblastic cells (SaOs-2) seeded on silicon substrates with different nano-scale surface patterns. Our findings suggest that substrate nanopattern geometry can differentially control early cell differentiation decisions. Interestingly, rescue of the differentiation process by supplementation of growth medium with soluble differentiation factors did not appear to compensate for the differences in the early cellular fate decisions observed on the different patterns. Critically, combining surface topography and soluble differentiation factors appeared to modulate the speed of the differentiation process and its shut down at the end of terminal differentiation. Taken together, our findings suggest that cells recognize physical nano-scale topography as an instructive signal that is integrated to fine-tune the multimodal control and guidance of cell behavior and cell fate. This information may find utility in the design of orthopedic and dental implants or innovative bio-materials for regenerative medicine.

A relevant increase in the electroanalytical application of sub-micrometer sized electrodes came with the development of arrays of nanoelectrodes. In the nanoelectrode ensembles (NEEs), the spatial distribution of the nanoelectrodes is random, while in the nanoelectrode arrays (NEAs) it is ordered. NEAs are typically fabricated by top-down microfabrication techniques, such as electron-beam lithography or nano-imprinting, while bottom-up technologies, such as the template methods and self-assembly are more often used for NEEs. NEEs/NEAs can exhibit three distinct response regimes depending on the scan rate or distance between the nanoelectrode elements: Total Overlap, Pure Radial and Linear Active. In the present work, NEAs are prepared by e-beam lithography and used for voltammetric measurements.

Organic thin film transistors were fabricated by vacuum evaporation of pentacene using different growth conditions in order to tune the pentacene layer morphology. We have performed in situ transport measurements on completed samples, and ex situ morphological characterization by atomic force microscopy. Electric properties of the microscopic interface environment at the drain/pentacene and source/pentacene interfaces were probed by Kelvin force microscopy. From the observed voltage drops at the metallic contacts we have calculated contact resistances that may be decomposed into contributions due to structural defects in the channel, due to structural defects at the metal/pentacene interface, and due to charge carrier injection at the source/pentacene interface. We observe that samples fabricated by different growth conditions exhibit different contact resistances. The most important variable contribution to the contact resistance is due to the charge carrier injection at the source/pentacene interface.

Organic photovoltaic cells (OPV) are among the most promising systems for energy extraction and conversion from renewable energy sources. However, major problem to be solved before industrial production could become economically viable is represented by their still low conversion efficiency. The organic solar cell architectures are presently the result of a compromise between achieving complete light absorption using active layers that are thicker than the optical absorption length and achieving efficient charge collection at the electrodes which is favoured in thinner layers. We present a concept and its experimental demonstration that would solve efficiently the above trade-off problem by making use of a new type of light trapping elements. The simple fabrication scheme, based on a self-aligned UV exposure process, suggests its potential up-scalability to large systems, at low production cost.

We have developed a fabrication methodology that relies on nanoimprint lithography (NIL), wet etching (Buffered Oxide Etch solution) and plasma etching in an Inductively Coupled Plasma (ICP); with our process we are able to pattern extended surface areas of about 1cm^2 with an array of rectangular channels or hemispherical holes of nanometric size. The fabricated samples are used in adsorption experiments to test recent theoretical predictions concerning the capillary condensation in capped capillaries.

We present the first results of microstructure replica with re-usable masters in poly vinyl alcohol (PVA). Microneedles of heights ranging from 500 to 1100@mm were fabricated through double-exposure deep X-ray lithography (DXRL) process and successfully replicated. A single PVA master was used as a template to successfully replicate up to 10 PMMA microneedle arrays, suggesting that this method might be a possible alternative to PDMS processes. A preliminary characterization of the relationship between the surface roughness of the substrates and the force required for demoulding was also performed.

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.

Islet transplantation has great potential in restoring normoglycemia in diabetic patients. However, current clinical islet transplantation is associated with high graft failure the reasons of which still remain obscure. It is noteworthy that the process of islet isolation exposes the islet to a variety of cellular stresses, including disruption of the cell-matrix relationship, an event associated with induction of apoptotic pathways. This may adversely affect islet viability and function leading to the observed failure of islet transplantation. The cell-matrix relationship, characterised by adhesion interactions between membrane integrin receptors and the extracellular matrix molecules at the nanoscale, is known to modulate cell survival and growth. The aim of this study is to present a unique method of fabricating large area artificial substrates with biomimetic nanoscale surface topography. The substrates were realised by thermal evaporation of tin on silicon wafers to form randomly assembled nano-islands. Using the nano-islands as masks, the wafers were plasma etched to transfer the pattern onto silicon. We then examined the hypothesis of whether beta-cell function and survival can be enhanced by optimized restoration of cell-matrix adhesion. The results of in vitro cell cultures show that insulinoma cells significantly adhered and enhanced insulin secretion when cultured on these nano-structured substrates compared to planar controls. With this unique fabrication process we propose a simple, robust and accessible technology for fabricating platforms for potential use in the investigation and modulation of early pancreatic beta-cell behaviour which may find utility in the development of strategies for pancreatic islet engineering and transplantation.

A major limitation in the translation of stem cells technology to clinical applications is the lack of efficient control over their proliferation and differentiation. Recent in vitro research findings suggest that biomaterials with nanoscale surface topography can influence cell behaviour like adhesion, proliferation and differentiation. Therefore, the identification of biomaterials that support appropriate ES cell attachment, proliferation and differentiation into cells of interest is an attractive strategy worth investigation. In this study we present the design and fabrication of thin films of gold with surface topography of varying roughness using a combination of microfabrication techniques. We then explored their biomimetic potential to direct differentiation of ES cell-derived neural precursors. Standard glass coverslips and tissue culture plastic were used as reference materials. Our preliminary results show that ES-derived neural precursors best adhered on gold and underwent the highest differentiation on gold films with root mean square surface roughness (Rq) of 21 nm (72 ± 6%) after five days of culture in the absence of traditional soluble neurotrophic factors. Moreover, when cells were seeded on a combination of micro-scale grooves with nanoscale surface roughness, axonal outgrowth orientation was observed to be influenced by the grating axis. This data identifies gold as a potential biomaterial candidate with suitable cytocompatibility for ES cell research. It further lends support to the hypothesis that biomaterial design may optimize ES cell-derived neural differentiation and organisation. This may find utility as a tool to synergically complement soluble chemical factors currently used in in vitro protocols for the stimulation and modelling of ES differentiation. Ultimately, substrate patterning may hold special utility in the design of neural prostheses because repair of neurological injuries requires directional guidance.

Maintaining the correct folding of cellular proteins is essential for preserving cellular homeostasis. Protein dishomeostasis, aberrant protein folding, and protein aggrega- tion are indeed involved in several diseases including cancer, aging-associated, and neurodegenerative disorders. Accumu- lation of protein aggregates can also be induced from a variety of stressful conditions, such as temperature increase or oxidative stress. In this work, we monitored by Fourier transform-infrared (FT-IR) microspectroscopy the response of live breast cancer MCF-7 and mammary breast adenocarcino- ma MDA-MB 231 cell lines to severe heat-shock (HS), caused by the rise of the cellular medium temperature from 37 ± 0.5 °C to 42 ± 0.5 °C. Through the study of the time-evolution of the second derivatives of the spectra and by the 2D correlation analysis of FT-IR absorbance data, we were able to identify a common sudden heat-shock response (HSR) among the two cell lines. The hyperfluidization of mammalian cell membranes, the transient increment of the signal lipids, as well as the alteration of proteome profile were all monitored within the first 40 min of stress application, while the persistent intracellular accumulation of extended β-folded protein aggregates was detected after 40 min up to 2 h. As a whole, this paper offers a further prove of the diagnostic capabilities of FT-IR microspectroscopy for monitoring in real-time the biochemical rearrangements undergone by live cells upon external stimulation.

Display Omitted A full 4¿ wafer is nanopatterned by an ultrafast thermal NIL process in 100µs.Stamps with integrated heater enable ultrafast cycles at very high temperature.The thermal cycle is implemented with a single short very intense current pulse.A new tool for the ultrafast NIL (or pulsed-NIL) process has been developed.The process applies to a wide range of thermoplastic materials. We present here an ultrafast thermal NIL technology, which enables the patterning of full wafers on the 100µs time-scale. This technique makes use of stamps with a heating layer integrated beneath their nanostructured surfaces. Injecting a single, short (

The fabrication of single electron transistors and/or highly sensitive biosensors is still a challenging task on account of the tight control required to get proper shapes and size of the electrodes. The nanosized tips and the separation of a few nanometers between electrode pairs are critical features. Conventional lithography is not suited to obtain these features because of the resolution limits, so that previous alternative approaches have involved the use of electron beam lithography, focused ion beam lithography or scanning probe nanolithography. The novel approach presented in this letter is the exploitation of X-ray lithography in the Elettra synchrotron to fabricate arrays of nanocontacts spaced a few nanometers, devoted to the design of a new class of nanodevices based on nanoparticles and/or single molecules, including single electron transistors and highly sensitive biosensors. The method to fabricate such devices is illustrated and discussed. Experimental details of the fabrication process are given and preliminary results are presented through SEM and AFM images. It is worth noting that this paper presents a viable method to produce nanocontacts by using the X-ray lithography by synchrotron radiation source, that has not yet been reported together with experimental, though preliminary, data. (c) 2006 Elsevier B.V. All rights reserved.

This paper describes a fabrication process of hollow microneedle arrays with a sharp beveled tip for transdermal drug delivery. A master is fabricated through a double deep x-ray lithography process. First, a polymethylmethacrylate (PMMA) sheet is exposed to produce single PMMA parts with a sawtooth profile. The tip angle of each tooth determines the final tip angle of the rnicroneedles. The PMMA parts are assembled and glued on a conductive substrate and then exposed through a second x-ray mask containing an array of hollow triangles as absorbing structures. A metal layer is then electrodeposited around the needles in order to form the future base of the array. A polyvinyl alcohol (PVA) solution is cast on top of the master to form a negative mold of the microneedle array after a low temperature curing and peel-off steps. A liquid PMMA solution is cast on top of the PVA negative mold and after the full PMMA polymerization the PVA is dissolved in water. This fabrication method can be performed in a non-clean room environment and requires little instrumentation. It is therefore compatible with a low-cost mass-fabrication scheme.

Pyramid wavefront sensors are the key components of new multiconjugate adaptive optics systems used for wavefront correction of terrestrial telescopes. The sensor consists of a very flat four faces pyramid made in a transparent material that requires an accurate control of the quality of its turned edges, its surfaces and the size of its pyramid tip. Moreover identical copies of these optical elements are needed to fulfil the requirements of the multiconjugate adaptive optics systems. This paper presents the fabrication method of Pyramid wavefront sensors using the LIGA process. Results are described and discussed.

Microcontact printing (μCP) is very attractive as a low cost, high throughput, and sub-100-nm resolution lithography. However, macroscopic distortions (thermal expansion, swelling by the solvent-assisted procedure of inking, externally induced strain) as well as microscopic distortions (membrane relaxation in wide unsupported areas and merging of close features) compromise the quality of pattern transfer. We show that ultrathin (

We present a new water-vapour-assisted nanoimprint lithography (NIL) process for the patterning of the conducting poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS). The process was optimized with respect to relative humidity, applied pressure and temperature (RH, p, T). The control of environmental humidity was found to be crucial. High quality nanostructures were reproducibly obtained at high relative humidity values (RH >= 75%), with sub-100 nm resolution features attaining aspect ratios as high as similar to 6 at similar to 95% RH. The developed process of water-vapour-assisted NIL (WVA-NIL) strongly affects the electronic properties of PEDOT: PSS. By current-voltage measurements and ultraviolet photoemission spectroscopy we demonstrate that the process parameters p, T and RH are correlated with changes of PEDOT: PSS conductivity, work function and states of the valence band. In particular, an increase in the films conductivity by factors as high as 105 and a large decrease in the work function, up to 1.5 eV, upon WVA-NIL processing were observed. Employed as an anode buffer layer in P3HT: ICBA bulk heterojunction solar cells, PEDOT: PSS processing was found to affect significantly the device performance.

This work focuses on the development of electrochemical impedance biosensors based on capacitance readout, for the detection of biomolecules in small sample volumes. We performed electrochemical impedance spectroscopy (EIS) measurements of DNA hybridization in electrochemical cells with microfabricated gold electrodes. The time stability of the device was tested in two different configurations: two microelectrodes in a microfluidic channel; two microelectrodes plus a reference electrode in an electrochemical cell. Our results demonstrate that the three-electrode setup is more stable, more reproducible, and suitable for real-time measurements. In the last part of the work we perform a test study of DNA hybridization in real time, and we show that the three-electrode configuration can measure the process in situ and in real time. (C) 2013 Elsevier B.V. All rights reserved.

To fabricate long lifetime polymer solar cells, understanding the fundamental aspects controlling the performances, stability and degradation of the devices is essential. In this study, we compare the chemical and electrical degradation behaviors of polymer solar cells based on active layers of semi-crystalline p-type polymer poly(3hexylthiophene) (P3HT) and different fullerene derivatives as acceptors. Photodegradation study by UV-visible and Fourier transform infrared (FTIR) spectroscopy and photovoltaic performance study by current-voltage measurement were done to understand and compare air stability of P3HT blended with different fullerenes. The used acceptors are indene-C(60) bisadduct (ICBA) and phenyl-C61-butyric acid methyl ester (PCBM). The obtained results show that solar cells fabricated from PCBM as acceptor are more stable than those based on ICBA. Based on the spectroscopic and electrical measurement results, it is safe to conclude that PCBM contributes more to stability of P3HT than ICBA, and that the degradation behavior is compatible with recently proposed mechanisms. Chemical properties of ICBA such as the low electron affinity could be responsible for the relative low stability of the device. (C) 2014 Elsevier B.V. All rights reserved.

We describe a scheme for the fabrication of sharp blazed gratings involving two cascaded steps of X-ray lithography (XRL) with electroplating (EP) steps interposed. The adopted iterative scheme enables the amplification by two orders of magnitude of the height of high-resolution structures of an original X-ray mask produced by Electron Beam Lithography (EBL), while minimizing the loss of lateral resolution. Nickel structures of up to 200 μm in height with blazed grating profile were obtained with The described approach is suitable for the fabrication of nickel structures, to be used in particular as master tools in hot embossing processes, in a broad range of optical applications requiring non-binary microstructures.

A technological scheme for the fabrication of metallic point contacts is presented. Nanoimprint lithography (NIL) (J. Vac. Sci. Technol. B, 14(6) (1996) 4129–4133) plays a key role in the process determining the critical dimension of the point contact. The pattern obtained by imprint has been studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The masking properties of the polymer film which also serves as an insulating layer in our device, separating the electrodes between which the point contact is located, have been controlled. Our study confirms that the imprint step involved in the process and the chosen thermoplastic polymer meet the requirements for fabricating nm-scale metallic point contacts.

The quest for efficient harvesting of solar radiation is one of the major areas of research in the renewable energy field. Through different photonic architectures it is possible to augment the optical absorption by trapping light within thin and ultra-thin films, the latter being desirable to decrease costs and efficiently extract the photogenerated charge carriers. Engineering the absorbing material at the nanoscale indeed leads to interferences that can significantly increase light absorption [1].

Guidance molecules, such as Sema3A or Netrin-1, can induce growth cone repulsion or attraction in the presence of a flat surface, but very little is known of the action of guidance molecules in the presence of obstacles. In order to address this issue, we analysed the action of Netrin-1 molecules in the presence of patterned polydimethylsiloxane (PDMS) surfaces with lines with a height varying from 100 to 600 nm. Filopodia can crawl over these lines easily, but not neurites. Indeed axons and thick dendrites are able to cross lines with a height of 100 nm, but progressively less when the line height is increased. When neurons are grown for 3 days over patterned surfaces it was possible to label selectively axons with axonal neurofilament marker SMI 312 and dendrites with microtubule associated protein 2 (MAP2): axons and dendrites do not differ in their ability to cross lines with a height varying from 100 to 600 nm. When axons and dendrites grow along lines, a clear staining for the adhesion marker paxillin was observed, but not when neurites cross the lines.