Additive nanomanufacturing: a review

Additive manufacturing has provided a pathway for inexpensive and flexible manufacturing of specialized components and one-off parts. At the nanoscale, such techniques are less ubiquitous. Manufacturing at the nanoscale is dominated by lithography tools that are too expensive for small- and medium-sized enterprises (SMEs) to invest in. Additive nanomanufacturing (ANM) empowers smaller facilities to design, create, and manufacture on their own while providing a wider material selection and flexible design. This is especially important as nanomanufacturing thus far is largely constrained to 2-dimensional patterning techniques and being able to manufacture in 3-dimensions could open up new concepts. In this review, we outline the state-of-the-art within ANM technologies such as electrohydrodynamic jet printing, dip-pen lithography, direct laser writing, and several single particle placement methods such as optical tweezers and electrokinetic nanomanipulation. The ANM technologies are compared in terms of deposition speed, resolution, and material selection and finally the future prospects of ANM are discussed. This review is up-to-date until April 2014

Estudio de la interfase en los hormigones reforzados con fibras

In a composite material that uses fibers as reinforcement, the breakage of the matrix is produced jointly with the separation of the fiber from the matrix. The mechanical behavior of the interface describes how fibers can work stabilizing the cracking process. The interface is the medium that puts the fiber on load, being the mechanical behavior of the interface and the strength of the fiber two important parameters to consider to characterize the general behavior of the composite. The present work studies the effect of several parameters on the behavior of the interface. Those parameters are the type of fiber, its geometry and dimension and the modified matrix and loading rate. An experimental technique was designed to allow testing the same set-up for pull-out tests in a quasistatic machine and Charpy pendulum. Modifications of the matrix by adding a mineral admixture improve the behavior of the interface as much as a 100%. It has been observed that combining the two actions, an improved matrix with crimped fibers, the type of failure can be modified. In this new type of failure, the fiber breaks consequently toughness decreases. Other parameters, as the loading rate and inclination of the fiber also affect the behavior of the interface.En un material compuesto que utiliza fibras como refuerzo, la rotura de la matriz se produce conjuntamente con la separación de la fibra de la matriz, por lo que el comportamiento mecánico de la interfase describe hasta que punto las fibras pueden trabajar como estabilizadores en el proceso defisuración. La interfase es el medio que pone en carga a la fibra y, por ello, la resistencia mecánica de la interfase y de la fibra son dos parámetros importantes a considerar para caracterizar el comportamiento general del composite. Este trabajo investiga el efecto de la variación del tipo de fibra, geometría y dimensión de las mismas y las modificaciones de la matriz y la velocidad de desplazamiento en el comportamiento de la interfase. Se ha puesto a punto una técnica experimental que permita utilizar la misma configuración del ensayo de pull-out en una prensa universal quasi-estática y en un pendido Charpy. Si mejoramos la matriz con la incorporación de una adición mineral se consiguen aumentar las resistencias hasta en un 100%. Al mismo tiempo se observa que combinando las dos acciones, una matriz con humo de sílice y una fibra de acero ondulada a lo largo de la generatriz se puede modificar el tipo de fallo, produciéndose la rotura de la fibra y, por lo tanto, con menor tenacidad. Con el aumento de la inclinación de la fibra y la velocidad de carga también se modifican las fuerzas de adherencia

Enhancing skills in solving open-ended problems using game-based exercises

Some requirements for engineering programmes, such as an ability to use the techniques, skills and modern engineering tools necessary for engineering practice, as well as an understanding of professional and ethical responsibility or an ability to communicate effectively, need new activities designed for measuring students’ progress. Negotiations take place continuously at any stage of a project and, so, the ability of engineers and managers to effectively carry out a negotiation is crucial for the success or failure of projects and businesses. Since it involves communication between individuals motivated to come together in an agreement for mutual benefit, it can be used to enhance these personal abilities. The main objective of this study was to evaluate the adequacy of mixing playing sessions and theory to maximise the students’ strategic vision in combination with negotiating skills. Results show that the combination of playing with theoretical training teaches students to strategise through analysis and discussion of alternatives. The outcome is then more optimised

Evaluation of bone marrow and blood cultures for the recovery of mycobacteria in the diagnosis of disseminated mycobacterial infections

AbstractThis study evaluated the validity of bone marrow (BM) and blood specimens for the diagnosis of disseminated mycobacterial infections (DMIs). From 1990 to February 1997, all specimens were processed with the lysis-centrifugation procedure; thereafter (until December 2001), they were processed with the BACTEC Myco/F Lytic system. Twenty-three paired BM-blood specimens with mycobacteria in at least one specimen were studied from 23 patients. The strains isolated were 14 Mycobacterium avium complex (MAC) and nine M. tuberculosis complex (MTBC). Blood specimens had a statistically significant greater sensitivity for the isolation of MAC than BM (100% vs. 57.1%, respectively), whereas sensitivity for the isolation of MTBC was equal for the two specimen types (66.7%). Although not statistically significant, the times required to detect mycobacteria from blood specimens were lower than those from BM in the MycoF/Lytic system. Overall, blood cultures represented a more sensitive and less invasive alternative to BM cultures for the diagnosis of disseminated mycobacteriosis caused by MAC, especially when the MycoF/Lytic system was used, but provided no advantage for the diagnosis of DMI caused by MTBC

Morphology of phase separated blends of poly(cyclohexyl methacrylate) with poly(vinyl acetate)

Blends of poly(vinyl acetate) (PVAc) and poly(cyclohexyl methacrylate) (PCHMA) labeled by copolymerization with 4-methacryloylamine-4′-nitrostilbene (Sb), with (1-pyrenylmethyl)methacrylate (Py) or with 3-(methacryloylamine)propyl-N-carbazole (Cbz), were prepared by casting dilute solutions in tetrahydrofurane (THF) or chloroform onto silanized glass plates. The resulting films were studied by epifluorescence microscopy, microfluorescence spectroscopy, DSC and optical microscopy. Epifluorescence micrography probes the chemical composition of the different regions in phase separated blends, with black areas corresponding to PVAc rich regions and colored areas corresponding to labeled PCHMA rich regions. The technique also visualizes primary and secondary morphologies, which depend on the composition of the polymer blend and on the casting solvent. Mixtures containing 80 wt % PCHMA show, in general, a bicontinuous primary morphology suggesting a spinodal demixing mechanism. Solvent effects are particularly relevant for 50% and 20% PCHMA samples showing morphologies composed of PCHMA rich domains, in a matrix of solvent-dependent compositions. Samples cast from chloroform are more homogeneous and the matrix is always highly fluorescent. In contrast, the domains of samples cast from THF are heterogeneous in size and shape and the matrix is non-fluorescent, being thus formed by nearly pure PVAc. Small voids are formed in the polymer-air interface. They are submicrometric for THF cast films and disappear with annealing at 122°C. For chloroform cast samples they are much less frequent and appear well ordered, forming a mostly hexatic two dimensional network.This work was supported by DCI (Spain) and EU (Brite-Euram) under grants BQU2000-0251 and BE-97-4672, respectively

Electronic transport and vibrational modes in the smallest molecular bridge: H2 in Pt nanocontacts

We present a state-of-the-art first-principles analysis of electronic transport in a Pt nanocontact in the presence of H2 which has been recently reported by Smit et al. in Nature 419, 906 (2002). Our results indicate that at the last stages of the breaking of the Pt nanocontact two basic forms of bridge involving H can appear. Our claim is, in contrast to Smit et al.'s, that the main conductance histogram peak at G approx 2e^2/h is not due to molecular H2, but to a complex Pt2H2 where the H2 molecule dissociates. A first-principles vibrational analysis that compares favorably with the experimental one also supports our claim .Comment: 5 pages, 3 figure

Detection system of magnetic nanoparticles in biological tissues by Magnetoencephalography

Magnetic nanoparticles are useful for a wide range of applications from data storage to medical imaging. Their unique features (controllable size in the nanoscale range, possibility to be coated with biological molecules, response to the application of a magnetic field...) make the development of a variety of medical applications possible, both for diagnosis and therapy [1-3]. On the other hand, Magnetoencephalography (MEG) is a non-invasive functional imaging technique that enables the description of the temporal and spatial patterns of brain activity in resting conditions or related to different basic cognitive processes, by detecting the weak magnetic fields generated by currents in the neurons [4,5]. The detection of the weak magnetic fields depends on gradiometer detection coils coupled to a superconducting quantum interference device (SQUID). However, MEG systems are not currently being used for the detection of MNPs in biological tissues. A system to newly detect Magnetic Nanoparticles (MNPs) in the brain and in biological tissues will be described. The method uses a commercial Magnetoencephalograph (MEG) and opens new possibilities to extend the use of MEG systems to new applications for both diagnosis and therapy of medical diseases, different from its common use in neurological diagnosis. To test the validity of the system, in this work, we will show its ability to detect MNPs in biological tissues and their possible use in diagnosis of cerebral brain microinjurie

Model Systems of Precursor Cellular Membranes: Long-Chain Alcohols Stabilize Spontaneously Formed Oleic Acid Vesicles

AbstractOleic acid vesicles have been used as model systems to study the properties of membranes that could be the evolutionary precursors of more complex, stable, and impermeable phospholipid biomembranes. Pure fatty acid vesicles in general show high sensitivity to ionic strength and pH variation, but there is growing evidence that this lack of stability can be counterbalanced through mixtures with other amphiphilic or surfactant compounds. Here, we present a systematic experimental analysis of the oleic acid system and explore the spontaneous formation of vesicles under different conditions, as well as the effects that alcohols and alkanes may have in the process. Our results support the hypothesis that alcohols (in particular 10- to 14-C-atom alcohols) contribute to the stability of oleic acid vesicles under a wider range of experimental conditions. Moreover, studies of mixed oleic-acid-alkane and oleic-acid-alcohol systems using infrared spectroscopy and Langmuir trough measurements indicate that precisely those alcohols that increased vesicle stability also decreased the mobility of oleic acid polar headgroups, as well as the area/molecule of lipid

Chemical Synthesis of PEDOT–Au Nanocomposite

In this work, gold-incorporated polyethylenedioxythiophene nanocomposite material has been synthesized chemically, employing reverse emulsion polymerization method. Infrared and Raman spectroscopic studies revealed that the polymerization of ethylenedioxythiophene leads to the formation of polymer polyethylenedioxythiophene incorporating gold nanoparticles. Scanning electron microscope studies showed the formation of polymer nanorods of 50–100 nm diameter and the X-ray diffraction analysis clearly indicates the presence of gold nanoparticles of 50 nm in size