1,721,007 research outputs found
Superhydrophilic properties driven by highly-regular laser-induced periodic structures on Si surface
No full textIn this work an investigation about the effects of high-speed, highly-regular laser induced periodic surface structures (HR-LIPSS) on wetting properties of silicon surface are presented and discussed. In order to investigate the influence of chemistry on wetting properties of textured surfaces, treatments were performed both under air and N2 shielding gas. The morphology was investigated by Scanning Electron Microscope (SEM), the chemistry by energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy and the wetting properties by camera recording. The results demonstrate substantial effects of HR-LIPSS on wetting properties of silicon surface. The hydrophilic Si surface becomes superhydrophilic after femtosecond nanopatterning and the addition of N2 in laser treated zone essentially influences the chemistry of the surface, this permits to control the water flowing and makes HR-LIPSS more flexible, bringing up to a new level of control of wettability properties for several applications
Implementation and Assessment of an Augmented Training Curriculum for Surgical Robotics
No full textThe integration of high-level assistance algorithms in surgical robotics training curricula may be beneficial in establishing a more comprehensive and robust skillset for aspiring surgeons, improving their clinical performance as a consequence. This work presents the development and validation of a haptic-enhanced Virtual Reality simulator for surgical robotics training, featuring 8 surgical tasks that the trainee can interact with thanks to the embedded physics engine. This virtual simulated environment is augmented by the introduction of high-level haptic interfaces for robotic assistance that aim at re-directing the motion of the trainee's hands and wrists toward targets or away from obstacles, and providing a quantitative performance score after the execution of each training exercise.An experimental study shows that the introduction of enhanced robotic assistance into a surgical robotics training curriculum improves performance during the training process and, crucially, promotes the transfer of the acquired skills to an unassisted surgical scenario, like the clinical one
Early stage in low-energy ion-induced damage on InP(110) surface
No full textThe change in the short-range order created by ion milling in the near surface region of InP single crystals wasinvestigated by primary beam diffraction modulated electron emission (PDMEE). The very early stage of the damagecreation by low energy (0.6-1 keV) Ar ions in normal and oblique incidence was studied. A simple model based on theweighted combination of perfectly crystalline and completely amorphous regions was used to model the experimental results.Evidence of a subsurface nucleation of the amorphization process was found. We also found that the total sputtering yield ismarkedly dependent on the ion dose, being on the undamaged surface much larger than its steady state value. Low energyelectron diffraction (LEED) measurements were also performed to correlate long-range and short-range order removal by ionbombardment. Finally, the ion damage on the GaAs and InP surfaces was comparatively discussed
Origin of Hydrophobicity in FIB-Nanostructured Si Surfaces
No full textSurface morphology has been demonstrated to influence the tribological properties at different scales, but the phenomena which occur at the nano-scale have not been completely understood. The present study reports on the effect of Focused Ion Beam nano-patterning on coefficient of friction (CoF) and adhesion of Si(001) surface covered by native oxide. Regular arrays of nano-grooves reduce both CoF and adhesion, related to a hydrophobic character of the patterned surface, but this effect disappears as soon as the separation among the nano-structures approaches the microscopic scale. The dependence of this hydrophobic effect on the pitch is not linked to the corresponding contact area. It has been found that each nano-structure is surrounded by a low-friction region which extends some hundreds nm from it. For pitch of 125 and 250nm these low-friction regions completely overlap, generating a consistent decrease in CoF and adhesion, while for pitch of 500 and 1000nm its effect is negligible. The low-friction regions were not observed in humidity free ambient, indicating that they are the origin of patterns hydrophobicity
Interfacial reactivity and morphology at the Au/NiO(001) interface
No full textThe interest on metal-oxide interfaces is stimulated stimulated by the applications in many fields, such as catalysis, magnetic ecording, hard coatings. In the first stages of growth, gold nanoparticles dispersed on different oxides exhibit unusual electronic properties, depending on cluster size and gold-substrate interaction [1,2]. In particular a partial charge transfer
can occur, especially when the substrate is defective since gold tends to nucleate on oxygen vacancies. Thus the properties of goldoxide systems are critically dependent on interface reactions, in turn influenced by substrate preparation. A deeper understanding of the reactivity at the gold-oxide interface is essential to determine and control properties and behaviour of supported gold clusters. In this work we present a study of Au nucleation on top of 10 ML NiO film on Ag(001). By means of XPS, XPD and STM/AFM we studied electronic properties and morphology of the first stages of growth. It was previously reported that deposition of 15 A Au on NiO/Ag(001) causes oxide reduction [3]. We provide detailed and quantitative description
of the chemical interactions at this interface. From these results we aim to determine a relation between NiO reduction and morphological modifications (cluster formation and step decoration) in order to understand the driving force of the reduction process. Similar metal-oxide interfaces have been
also studied [4,5] to identify a general trend
in nucleation and reaction processes. In particular Fe, Pt on NiO and Fe, Pt, Au on MgO have been comparatively investigated.
[1] A. Sanchez, S. Abbet, U. Heiz, W.-D. Schneider, H. Hkkinen, R.N. Barnett, U. Landman, J. Phys. Chem. A 103(1999) 9573
[2] Z. Yang, R. Wu, D.W. Goodman, Phys. Rev. B 61 (2000) 14066
[3] R. de Masi, D. Reinicke, F. Mller, P. Steiner, S. Hfner, Surf. Sci. 515 (2002) 523
[4] S. Benedetti, P. Luches, M. Liberati, S. Valeri, Surf. Sci. 572 (2004) L348
[5] P. Luches, S. Benedetti, M. Liberati, F. Boscherini, I.I. Pronin, S. Valeri, Surf. Sci., in pres
Performance-Driven Tasks with Adaptive Difficulty for Enhanced Surgical Robotics Training
Full text linkSurgical robotics training most often occurs through standardized curricula and exercises that lack customization and do not adapt to the different levels of proficiency that trainees often present. This work proposes a Virtual Reality (VR) simulator for surgical robotics that autonomously adjusts difficulty levels based on trainee performance, aiming to enhance skill retention and transfer. The study employs a performance-based adaptive difficulty approach, dynamically adjusting parameters of each task's morphology to match individual proficiency levels. The proposed adaptive simulator is evaluated against a non-adaptive counterpart through a week-long training program. The results demonstrate the effectiveness of the adaptive simulator in enhancing performance at higher difficulty levels, supporting its potential to benefit surgical education by providing a tailored and scalable training approach
Size-dependence transition from nano-friction to micro-friction
No full textThe interpretation of tribological processes is presently very different for nano-scale and micro-scale phenomena. This is mainly related to the presence of adhesive forces, which are not negligible at the nano-scale and, in some cases, dominate the tribological behaviour of the system. The morphological characteristics of sliding surfaces have been demonstrated to strongly influence both the nano-scale and the micro-scale tribology [1-4]. The phenomena which rule these properties are different depending on the dimensions of surface micro/nano-structures, on the contact area and on the applied load. At the micro-scale the presence of a regular array of micro-cavities could lead to the reduction of friction and wear, due to the enhancement of the hydrodynamic lift-off effect and to the role played by the micro-cavities as lubricant reservoir and debris pocket [1, 2]. At the nano-scale parallel nano-grooves induce a hydrophobic character to the surface, resulting in a reduction of the coefficient of friction and adhesion [3, 4].
The aim of the present study is to determine the critical size at which the transition from nano- to micro-scale regimes occurs, investigating the effect of surface patterning on the tribological properties of Si(100). With this purpose the Si flat surface have been patterned by means of Focused Ion Beam with regular arrays of parallel grooves 50nm wide and 4nm deep, varying the pitch from 125nm to 1m. Adhesion and friction have been studied as a function of the pitch by means of AFM in air and in vacuum, using a dedicated flat tip sensitive to the integrated effect of the nano-structures on the tribology of the system. The hydrophobicity of 125nm pitch array, already described in ref. 4, decreases between 400 and 500nm pitch, resulting almost absent for larger values. This finding identifies 400-500nm pitch interval as the threshold between nano- and micro-scale regimes.
This research has been supported by PRRIITT (Regione Emilia Romagna) and Centro Interdipartimentale per la Ricerca Applicata e i Servizi nella Meccanica Avanzata e nella Motoristica (Università di Modena e Reggio Emilia).
[1] A. Kovalchenko et al., Tribol. Int. 38 (2005) 219.
[2] A. Borghi et al., Wear 265 7-8 (2008) 1046.
[3] Y. Ando, Tribo. Lett. 19 (2005) 29.
[4] D. Marchetto et al., Wear 268 (2010) 488
Tribology and wettability of nano-machined silicon rough surfaces
No full text1 – Introduction
The more and more pressing demand for eliminating liquid lubricants in mechanical devices, due to their environmental costs, represents an important challenge for the tribological community. Low-friction coatings, like layered materials (graphite, Mo2S), soft metals (Ag, Au), non-layered metal oxides (MoO3, V2O5), can substitute liquid lubricants, but presently they are characterized by poor mechanical properties. On the other hand, hard ceramic coatings, like CrN, TiN, TiCN, TiAlN, have been studied for the last three decades for their high hardness, chemical inertness, high oxidation resistance and low wear rate.
The aim of our study is to couple the properties of hard ceramics with those of soft metals low friction coatings. The nanostructuring of CrN-Ag ternary coating represents an appealing solution.
2 – Main Body of Text
We studied the tribo-mechanical properties of CrN-Ag ternary coatings, where Ag clusters are dispersed in a CrN thick film. Some preliminary tests were also performed on a similar system, composed by Ag/CrN multilayers. CrN-Ag composite coatings were deposited on Si(100) and on a steel (20MnCr5) using PVD Magnetron Sputtering in a mixed N2+Ar atmosphere (P=5mtorr), with temperature ranging from RT to 500°. Structure, composition and morphology of both systems were characterized by Auger Electron Spectroscopy, X-rays diffraction and cross sectional analysis (depth-profiling AES, FIB cross section). The co-deposition of CrN and Ag in N2 atmosphere leads to the formation of a composite nanostructured coating, where Ag clusters behave as solid lubricant in the hard CrN bulk.
Tribo-mechanical properties were measured with a ball-on-disc tribometer and a Berckovich nanoindenter.
3 – Conclusion
By tuning the preparation conditions we were able to control the size, the distribution and the self organization of Ag nanoclusters in the CrN matrix, thus controlling frictional behavior
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
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