Abstract: In modern biomaterial design the generation of an environment mimicking some of the extracellular matrix
features is envisaged to support molecular cross-talk between cells and scaffolds during tissue formation/
remodeling. In bone substitutes chemical biomimesis has been particularly exploited; conversely, the
relevance of pre-determined scaffold architecture for regenerated bone outputs is still unclear. Thus we
aimed to demonstrate that a different organization of collagen fibers within newly formed bone under
unloading conditions can be generated by differently architectured scaffolds. An ordered and confined
geometry of hydroxyapatite foams concentrated collagen fibers within the pores, and triggered their
self-assembly in a cholesteric-banded pattern, resulting in compact lamellar bone. Conversely, when
progenitor cells were loaded onto nanofibrous collagen-based sponges, new collagen fibers were distributed
in a nematic phase, resulting mostly in woven isotropic bone. Thus specific biomaterial design relevantly
contributes to properly drive collagen fibers assembly to target bone regeneration.
Abstract: We demonstrate the possibility of using a simple functionalization procedure, based on an initial vapour-phase silanization, to control the size and functionality of solid state nanopores. The presented results show that, by varying the silanization time, it is possible to modify the efficiency of probe molecule attachment, thus shrinking the pore to the chosen size, while introducing a specific sensing selectivity. The proposed method allows us to tune the nanopore biosensor adapting it to the specific final application, and it can be efficiently applied when the pore initial diameter does not exceed a limit dimension related to the mean free path of the silane molecules at the working pressure.
Abstract: A Focused Ion Beam (FIB)-patterned silicon mould is used to fabricate elastomeric nanostructures, whose cross-section can be dynamically and reversibly tuned by applying a controlled mechanical stress. Direct-write, based on FIB milling, allows the fabrication of nanostructures with a variety of different geometries, aspect ratio, spacing and distribution offering a higher flexibility compared to other nanopatterning approaches. Moreover, a simple double replication process based on poly (dimethylsiloxane) permits a strong reduction of the fabrication costs that makes this approach well-suited for the production of low cost nanofluidic devices. DNA stretching and single molecule manipulation capabilities of these platforms have been successfully demonstrated.
Abstract: We present the development and the electrical characterization of a polymeric nanochannel device. Standard microfabrication coupled to Focused Ion Beam (FIB) nanofabrication is used to fabricate a silicon master, which can be then replicated in a polymeric material by soft lithography. Such an elastomeric nanochannel device is used to study DNA translocation events during electrophoresis experiments. Our results demonstrate that an easy and low cost fabrication technique allows creation of a low noise device for single molecule analysis.
Abstract: We present data concerning the electrical properties of a class of biosensor devices based on bio-functionalized solid state nanopores able to detect different kinds of interactions between probe molecules, chemically attached to the pore surface, and target molecules present in solution and electrophoretically drawn through the nanometric channel. The great potentiality of this approach resides in the fact that the functionalization of a quite large pore (up to 50âÂÂ60ànm) allows a sufficient diameter reduction for the attainment of a single molecule sensing dimension and selective activation, without the need for further material deposition, such as metal or oxides, or localized surface modification. The results indicate that it will be possible, in the near future, to conceive and design devices for parallel analysis of biological samples made of arrays of nanopores differently functionalized, fabricated by standard lithographic techniques, with important applications in the field of molecular diagnosis.
Abstract: The possible use of nanopores for single DNA molecules biosensing has been demonstrated, but much remains to do in order to develop advanced engineered devices with enhanced stability, and controlled geometry and surface properties. Here we present morphological and electrical characterization of solid state silicon nitride nanopores fabricated by focused ion beam direct milling and chemically functionalized by probe oligonucleotides, with the final aim of developing a versatile tool for biosensing and gene expression profiling.
Abstract: Recently, nanopore technology has been introduced for genome analysis. Here we show results related to the possibility of preparing "engineered solid state nanopores". The nanopores were fabricated on a suspended Si3N4 membrane by Focused Ion Beam (FIB) drilling and chemically functionalized in order to covalently bind oligonucleoticles (probes) on their surface. Our data show the stable effect of DNA attachment on the ionic current measured through the nanopore, making it possible to conceive and develop a selective biosensor for gene expression profiling. (c) 2008 Elsevier Ltd. All rights reserved.
Abstract: A quantitative surface reconstruction technique has been developed for the geometric characterization of three-dimensional structures by using a combined focused ion beam-scanning electron microscopy (FIB-SEM) instrument. A regular pattern of lines is milled at normal incidence on the sample to be characterized and an image is acquired at a large tilt angle. By analyzing the pattern under the tilted view, a quantitative estimation of surface heights is obtained. The technique has been applied to a test sample and nanoscale resolution has been achieved. The reported results are validated by a comparison with atomic force microscopy measurements. (C) 2009 Elsevier B.V. All rights reserved.
Abstract: The leak devices most frequently used to calibrate leak-detection instruments are permeation leaks. These devices are very sensitive to temperature and can only be used with helium. The physical-leak types that could overcome this limits are prone to clog and their minimum size (about 1 mu m) limits their applicability in the lowest flow range. Here, the authors propose a fabrication technique by means of focused-ion beam with which, in suitable materials, they are able to produce nanometer orifices. These devices [Universitagrave degli Studi di Genova, Italian Patent No., TO2008A000683 (18 September 2008)] work in the molecular-flow regime up to atmospheric pressure and do not clog. Other advantageous characteristics are the possibility of obtaining leak rates in the range equal to those of the permeation type and the linear dependence of the throughput on the inlet pressure.
Abstract: In recent years there has been a rapid increase in nanotechnology applications to medicine in order to prevent and treat diseases in the human body. The established and future applications have the potential to dramatically change medical science. The present paper will give a few examples that could transform common medical procedures.
Abstract: The focused ion beam (FIB) microscope is a tool that has a Widespread use in the field of material science because it is able to micromachining with high resolution imaging thus therefore enhancing it broad range of both fundamental and technological applications in material science. The FIB is based oil a beam of Ga ions Which sputter the sample enabling precise machining at the nanometer/micrometer scale. The FIB instruments received particular attentions in the 1980s when the semiconductor industry used it as offline equipment for mask or circuit repair, but only in the 1990s the FIB was used in research laboratory. Nowadays there are commercial instruments (Dual Beam FIB / SEM) that integrate the precision cross section power of a FIB with the high resolution imaging of an SI-M creating a powerful cross section and imaging tool. The combined SEM capability allows for real time monitoring of the FIB cuts with a higher resolution.
Abstract: In this work we present our results concerning the formation of self-organized nanoscale structures during the bombardment with a low-energy defocused Ar ion beam. We studied glass surfaces because of their physical properties, technological interest and cheapness. The evolution of sample surface was studied ex situ by atomic force microscopy. We found, in agreement with Bradley and Harper, a morphology characterized by a regular ripple structure with the wave vector perpendicular or parallel to the ion beam direction. This structure periodicity was found to vary in the range 90-350 nm with a linear time evolution. In order to gain further information about the sputtering process and for comparison with the existing continuum theories of surface erosion, we studied the scaling behaviour of surface roughness. (c) 2005 Elsevier B.V. All rights reserved.
Abstract: We demonstrate that a combination of ion sputtering and soft lithography is an alternative and effective way of nanostructuring soft matter. We create self-organized nanoscale structures on a glass template by irradiating the surface with a defocused, low energy Ar ion beam. Capillary force lithography is then used to transfer the pattern, exploiting the glass transition of polymeric layers. In particular, we demonstrate the pattern transfer of a periodic 150 nm fipple structure onto an organic compound, This new, unconventional combination is then a low-cost strategy that opens the way to a variety of applications in the field of organic-based devices.
Abstract: We have developed and tested a vacuum suitcase which allows to transport samples under ultrahigh vacuum (UHV) conditions. The suitcase is pumped by a new performant pumping system based on a getter pump, and it reaches an ultimate pressure lower than 3x10(-11) mbar, which is 2 orders of magnitude better than in the existing projects. Furthermore it has no need for a continuos power supply, no electric or magnetic field, low weight, low cost, and compactness. In order to transfer the sample from the suitcase to the main experimental chamber, in a short time (about 1 h) and under UHV conditions, we have also developed a turbo pumped buffer chamber equipped with a cold trap. (C) 2005 American Institute of Physics.
Abstract: Metal surfaces can be easily nanopatterned via ion sputtering: mounds or ripples can be created depending on the surface symmetry and temperature. However, in many cases these structures are unstable at room temperature and above, due to the adatom fast diffusion. This fact prevents the use of such systems as substrate or nanostamps for a technological implementation. In this paper we present a spot profile analysis low energy electron diffraction (SPA-LEED) study on the nanopatterning of a Rh(110) single crystal. Like the other (110) metal surfaces, previously investigated, also Rh(110) shows for increasing temperatures a transition between different rippled morphologies. The main advantage of this system is its stability at room temperature. From SPA-LEED data we can measure the structural features (average periodicity and local faceting) of the observed rippled structures. (c) 2005 Elsevier B.V. All rights reserved.
Abstract: We have developed a new type of nonevaporable getter (NEG) pump. It is based on the getter strip St707, produced by SAES getters S.p.A, fitted into a CF-flanged container. The pump is activated at 400degreesC for 1 h and its pumping behavior is studied for H-2, CO, and N-2. The pumping speed is about 500 liters/s for H-2, 230 liters/ for CO, and 130 liters/s for N-2, which is in good agreement with our theoretical pumping model. While its performance is similar to those of commercial NEG pumps, it is definitely more compact, inexpensive, and easy to use. When coupled with single-penning cell, our NEG pump can replace conventional ion pumps in the design of compact ultrahigh vacuum (UHV) systems. Its first application will be as an efficient and compact pumping device for portable UHV enclosure. (C) 2004 American Institute of Physics.
Abstract: Commercial He mass spectrometer leak detectors usually do not provide sufficient sensitivity to perform accurate measurements of the permeation rate of He through glass. Ultrasensitive dedicated systems have adeguate sensitivity but involve high costs and complex procedures. However, both cryogenics and photomultiplier technology routinely demand this goal. Here, we propose a novel method to increase the sensitivity of commercial devices to easily measure accurate permeation rate. We modified a commercial leak detector by reducing the pumping speed at the inlet of the rotary pump, thus increasing its sensitivity by one order of magnitude. The modified detector was used to measure the leak rate of the permeation of He through the glass walls of a photomultiplier. Further improvements made to decrease the minimum detectable signal were limited by the high ultimate pressure in the spectrometer tube. (C) 2004 American Vacuum Society.
