Gianluca Alaimo

Characterization of 3D-printed dielectric substrates with different infill for microwave applications

This paper presents the characterization of a 3D printed material based on Ninjaflex filament, through different techniques: the dielectric properties of the material are preliminary retrieved by a waveguide-based method, where a 3D-printed dielectric sample is inserted into a hollow metallic waveguide: this method allows for an accurate and narrow-band characterization. Subsequently, two microstrip lines with different length, realized on a 3D-printed substrate, are used for the broadband characterization in the frequency band from 2 GHz to 20 GHz. The effect of the infill percentage on the dielectric permittivity and loss tangent of the printed material are rigorously investigated and experimentally demonstrated, showing a large tunability when varying the infill from 25% to 100%. These results pave the road to the implementation of novel microwave components, based on the local variation of the dielectric permittivity, and suggest a technique to effectively reduce dielectric losses.

Multi-objective optimization of nitinol stent design

Nitinol stents continuously experience loadings due to pulsatile pressure, thus a given stent design should possess an adequate fatigue strength and, at the same time, it should guarantee a sufficient vessel scaffolding. The present study proposes an optimization framework aiming at increasing the fatigue life reducing the maximum strut strain along the structure through a local modification of the strut profile.The adopted computational framework relies on nonlinear structural finite element analysis combined with a Multi Objective Genetic Algorithm, based on Kriging response surfaces. In particular, such an approach is used to investigate the design optimization of planar stent cell.The results of the strut profile optimization confirm the key role of a tapered strut design to enhance the stent fatigue strength, suggesting that it is possible to achieve a marked improvement of both the fatigue safety factor and the scaffolding capability simultaneously. The present study underlines the value of advanced engineering tools to optimize the design of medical devices.

Finite element analysis of Additive Manufacturing based on Fused Deposition Modeling (FDM): distortion prediction and comparison with experimental data.

Additive manufacturing (or three-dimensional (3D) printing) is constantly growing as an innovative process for the production of complex-shape components. Among the seven recognized 3D printing technologies, fused deposition modeling (FDM) covers a very important role, not only for producing representative 3D models, but, mainly due to the development of innovative material like Peek and Ultem, also for realizing structurally functional components. However, being FDM a production process involving high thermal gradients, non-negligible deformations and residual stresses may affect the 3D printed component. In this work we focus on meso/macroscopic simulations of the FDM process using ABAQUS software. After describing in detail the methodological process, we investigate the impact of several parameters and modeling choices (e.g., mesh size, material model, time-step size) on simulation outcomes and we validate the obtained results with experimental measurements. [DOI: 10.1115/1.4041626]

3D Printing Technology for Buildings’ Accessibility: The Tactile Map for MTE Museum in Pavia

3D printing technology is an innovative manufacturing technology used in several disciplines, whose number and diversity are growing day by day. The development of devices to improve the accessibility of buildings and urban spaces for people with disabilities through 3D printing technology is still not broadly explored. The present study is focused on filling this gap, with the realization of a tactile map of the MTE (Museum of Electrical Technology) of the University of Pavia (Italy) for blind and visually impaired people. The tactile map represents the building plan with all the information to guide the visit. The device is the result of a research process which is made by several steps and experimental tests, aimed at setting the best 3D printing profiles to meet all the requirements of the end-users. This paper describes methods and strategies applied to reach these goals: it underlines the social and technical approaches, the experimental phases and its possible future developments.

3-D Printed Substrate Integrated Slab Waveguide for Single-Mode Bandwidth Enhancement

This letter presents the implementation of a broadband substrate integrated waveguide (SIW) by an additive manufacturing technique. A 3-D printed material based on Ninjaflex filament has been realized by fused deposition modeling. By changing the infill percentage, printed materials with different dielectric properties have been fabricated and experimentally characterized. Two materials obtained from the same filament with different infill percentages have been used for the implementation of a substrate integrated slab waveguide (SISW), which allows increasing the single-mode bandwidth compared with that of a standard SIW. The experimental results for the fundamental and second modes of SIW and SISW show a 50% bandwidth enhancement.