1,721,005 research outputs found
Fast formation of ripples induced by AFM. A new method for patterning polymers on nanoscale
No full textThe possibility to control the assembly of molecules on a given substrate is particularly important for polymeric systems. Self-assembly of polymer chains on a substrate can be controlled by modifying selectively the chemistry of the substrate surface and/or the polymer itself in order to create patterned polymer films with tailored length scales. A novel tool to change the polymer morphology in order to achieve the requested superficial structures and textures is the atomic force microscopy (AFM). In this paper, we shall demonstrate how to obtain ordered ripple structures induced by an AFM tip on a polymer thin film. It is well known that a polymer surface scanned by a probe tip can change its morphology assuming typical ripple structures. These structures however are expected to be formed for high applied loads (> 10 nN) and after many scanning cycles (> 10). On the contrary, we shall show how to obtain the ripple formation just by a single AFM scan and for relatively low applied loads. Such ripple structures can be modulated and modified by changing the applied load, scanning velocity and angle. In this way, it is possible to obtain sinusoidal structures with suitable amplitude, periodicity and orientation. Beyond the general contribution to the development of nanolithography, the patterns obtained by this method can find many applications in biomaterial polymer science (such as scaffolds for cell proliferation in tissue engineering). (c) 2006 Elsevier B.V. All rights reserved
Novel Ultrathin Films Based on a Blend of PEG- b-PCL and PLLA and Doped with ZnO Nanoparticles
No full textIn this paper, a novel nanofilm type is proposed based on a blend of poly(ethylene glycol)-block-poly(ε-caprolactone) methyl ether (PEG-b-PCL) and poly(l-lactic acid), doped with zinc oxide nanoparticles (ZnO NPs) at different concentrations (0.1, 1, and 10 mg/mL). All nanofilm types were featured by a thickness value of ∼500 nm. Increasing ZnO NP concentrations implied larger roughness values (∼22 nm for the bare nanofilm and ∼67 nm for the films with 10 mg/mL of NPs), larger piezoelectricity (average d33 coefficient for the film up to ∼1.98 pm/V), and elastic modulus: the nanofilms doped with 1 and 10 mg/mL of NPs were much stiffer than the nondoped controls and nanofilms doped with 0.1 mg/mL of NPs. The ZnO NP content was also directly proportional to the material melting point and crystallinity and inversely proportional to the material degradation rate, thus highlighting the stabilization role of ZnO particles. In vitro tests were carried out with cells of the musculoskeletal apparatus (fibroblasts, osteoblasts, chondrocytes, and myoblasts). All cell types showed good adhesion and viability on all substrate formulations. Interestingly, a higher content of ZnO NPs in the matrix demonstrated higher bioactivity, boosting the metabolic activity of fibroblasts, myoblasts, and chondrocytes and enhancing the osteogenic and myogenic differentiation. These findings demonstrated the potential of these nanocomposite matrices for regenerative medicine applications, such as tissue engineering
Investigation of structural relaxation and surface modification of ultrathin films of poly(ethylene terephthalate)
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Mapping the mechanical properties of a graphene drum at the nanoscale
Full text linkThe operation of graphene-based nanoelectromechanical systems (NEMS) crucially depends on the local mechanical characteristics of the graphene drum resonator. In particular, inhomogeneity in the residual strain (pre-strain) of the graphene membrane may affect the vibration dynamics as well as the energy dissipation. Despite its importance, achieving a precise local mapping of the pre-strain of a graphene membrane remains challenging. Here, we correlate scanning-probe force microscopy and Raman spectroscopy to map the local mechanical properties of circular monolayer-graphene drums. At odds with other techniques, we obtain maps of the membrane pre-strain with nanometric resolution and measure the effective Young's modulus in a non invasive way. Moreover, we show that the common topographic artefacts stemming from tip-induced deformations can be precisely corrected using the information derived from force-spectroscopy data. As a result, the local map of the pre-strain can be correlated with the true morphology of the graphene drum. Our analysis demonstrates that graphene resonators can be characterized by a non-flat morphology and a non-uniform pre-strain distribution, as a consequence of complex boundary conditions at the edge of the membrane and in correlation with local material defects. Since these non-ideal features are strictly related to the growth and the fabrication procedures, our method can provide a useful screening tool for the development of 2D materials-based NEMSs
Nano-sized optical devices for applications in proteomics and biomolecular electronics: engineered green fluorescence proteins
No full textFunctional Nanomaterials is the first and unique compilation of the state-of-the-art review chapters covering all aspects of functional nanomaterials and their applications. Nanotechnology has led to a profound paradigm shift after the developments in recent years and after being classified as one of the most important areas of impending technology by the U.S. government. Novel functional nanomaterials are the basis of newly emerging nanotechnologies for various device applications. This book with 30 chapters reflects the tremendous world-wide interest in functional nanostructured materials. The wide variety of topics covered in this book is interesting for professionals working in the fundamental and applied research. The book covers major classes of nanomaterials such as carbon nanotubes, carbon and polymer nanofibers, nanoparticles, nanocomposites, nanosheets, fullerenes, supramolecular and self-assembled nanostructures, and many other types of nanomaterials. In addition, thi..
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
THz differential near-field scanning optical microscopy for biological applications
No full textThe work describes a differential near-field scanning optical microscopy (DNSOM) mechanism, which represents a valuable tool for imaging with sub-wavelength resolution. In this approach the acquisition is carried out using squared apertures with dimensions comparable with the wavelength. The aperture, mounted on a xy translational stage driven with piezo-actuators, is scanned in the near field of the object of interest, illuminated by a laser source. In the measurements, a THz quantum cascade laser (QCL) laser is employed emitting at 2.9 THz.The resolution is presently limited by the numerical aperture of the light collection system and by the relative aperture-sample distance. Next steps consist in further improvements of the system in order to reach a resolution of ~ 1 mum and in the spectroscopic analysis of biological samples
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Evidence of diffusive fractal aggregation of TiO2 nanoparticles by femtosecond laser ablation at ambient conditions
No full textThe specific mechanisms which lead tothe formation of fractal nanostructuresbypulsed laser deposition remain elusive despite intense research efforts, motivated mainly by the technological interest in obtaining tailored nanostructures with simple and scalable production methods. Here we focus on fractal nanostructures of titanium dioxide, TiO2, a strategic material for many applications, obtainedby femtosecond laser ablation atambient conditions.We compare a theoretical model of fractal formation with experimental data. The comparison of theory and experiment confirms that fractal aggregates are formed after landing of the ablated material on the substrate surface by a simple diffusive mechanism. Wemodel the fractal formation through extensive Monte Carlo simulations based ona set of minimal assumptions: TiO2 nanoparticles arrive already formed onthe substrate, then they diffuseinasize/mass independent way and stick irreversibly upon touching, thus forming fractal clusters. Despite its simplicity, our model explains the main features of the fractal structures arising from the complex interaction of large TiO2 nanoparticles with different substrates. Indeed our model is able to reproduce both the fractal dimensions and the area distributions of the nanostructures for different densities of the ablated material. Finally we discuss the role of the thermal conductivity of the substrate and the laser fluence on the properties of the fractal nanostructures. Our results represent an advancement towards controlling the production of fractal nanostructures by pulsed laser deposition
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