Piezo-tunneling strain sensors integrated on plastic by combining vacuum thin film coatings and 3D printing technologies

There is a growing demand for the integration of sensor functions on flexible substrates for wearable electronics, robotics or medical monitoring. For this, it is necessary to develop strain gauges both sensitive and integrable at low cost with a low thermal budget. The gauge factor of metal/insulator/metal piezo-tunneling strain sensors is first measured as a function of applied current and polarity, for different electrode materials (Al, Pt or Pd) and insulator (Al₂O₃) thicknesses. A maximum gauge factor of 90 is obtained with an Al/Al₂O₃ (10 nm)/Al junction and top electrode injection. Results are discussed based on the Fowler–Nordheim model and it is shown that the electron effective mass in Al₂O₃ most likely plays a major role in the observed mechano-sensitivity. Next, the feasibility of a low-pressure sensor demonstrator based on a 3D-printing process on a polymer substrate is shown with a sensitivity of 0.19 bar⁻¹ in the 0–450 mbar range.

     

Heat‐Free Fabrication of Metallic Interconnects for Flexible/Wearable Devices

Exploiting interfacial excess (Γ), Laplace pressure jump (ΔP), surface work, and coupling them to surface reactivity have led to the synthesis of undercooled metal particles. Metastability is maintained by a core–shell particle architecture. Fracture of the thin shell leads to solidification with concomitant sintering. Applying Scherer's constitutive model for load‐driven viscous sintering on the undercooled particles implies that they can form conductive traces. Combining metastability to eliminate heat and robustness of viscous sintering, an array of conductive metallic traces can be prepared, leading to plethora of devices on various flexible and/or heat sensitive substrates. Besides mechanical sintering, chemical sintering can be performed, which negates the need of either heat or load. In the latter, connectivity is hypothesized to occur via a Frenkel's theory of sintering type mechanism. This work reports heat‐free, ambient fabrication of metallic conductive interconnects and traces on all types of substrates.     

Low-latency and high-throughput software turbo decoders on multi-core architectures

Annals of Telecommunications - In the last few years, with the advent of a software-defined radio (SDR), the processor cores were stated to be an efficient solution to execute the physical layer...     

Emulsion-Templated Poly(N-Isopropylacrylamide) Shells Formed by Thermo-Enhanced Interfacial Complexation

The encapsulation of fragile biomacromolecules is crucial in many biotechnological applications but remains challenging. Interfacial complexation (IC) in water-in-oil emulsions proves to be an efficient process for the formation of protective polymer layers at the surface of capsule-precursor water droplets. In this work, the enhancement of conventional IC by introducing thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) strands in the interfacial polymer layer is described. Surfactant-polymer IC is implemented in water-in-fluorocarbon oil emulsions between a water-soluble poly(L-lysine)-g-poly(N-isopropylacrylamide) cationic copolymer (PLL-g-PNIPAM) and an oil-soluble anionic surfactant. Fluorescence imaging demonstrates that the thermal collapse transition of PNIPAM strands, triggered by gentle heating, induces an enrichment of the polymer layer initially formed by IC. Spontaneous co-precipitation of nanoparticles initially dispersed in the aqueous cores—with no specific treatment—is also achieved upon PNIPAM transition. This process is leveraged to irreversibly segregate these nanoparticles in the interfacial polymer layer, resulting in gel-like mixed shells. Thermo-enhancement of conventional IC is thus a promising approach for the straightforward formation, strengthening, and functionalization of capsule shells. As implemented in mild conditions, thermo-enhanced IC is additionally compatible with the encapsulation of proteins, opening new opportunities for delivery systems of biomacromolecules.     

Transport layer for cooperative multimedia applications

This paper presents work carried out within the Cesame project for the design of a multimedia highspeed distributed transport provider. The term transport provider is used to target a reference framework but does not preclude any standardized reference model. It gives the objectives and relates the main contributions obtained during the first year of the project. The goal of this task is to monitor, select and design services, protocols and mechanisms for defining a transport provider to support distributed multimedia services. As far as architectural aspects are concerned, a refinement of reference models is mandatory, and work on this topic has already been started within several institutions. Moreover, it is worth to mention that the transport provider will have first to run on top ofAtm/Aal networks and is expected on top of other networks.     

Al matrix composites fabricated by solid-state cold spray deposition:A critical review

Cold spraying(CS),or cold gas dynamic spray(CGDS),is an emerging solid-state powder deposition process,allowing fast and mass production and restoration of metallic components.CS of metal matrix composites(MMCs)has attracted increasing attention from academia and industry over the last decades,especially in the area of Al matrix composites(AMCs),which have demonstrated a high potential for applications in aerospace,automotive,and electronics industries.This article aims to summarize the recent development of CS-processed AMCs in terms of composite powder preparation,deposition pro-cessing,microstructure evolution,mechanical and corrosion properties.Furthermore,this review also reports the relevant research progress with the focus on post-treatments of the AMCs for CS additive manufacturing applications including heat treatment,hot rolling,and friction stir processing.Finally,the challenges and perspectives on the fabrication of advanced AMCs by CS are addressed.     

Bayesian Analysis in Partially Accelerated Life Tests for Weighted Lomax Distribution

Accelerated life testing has been widely used in product life testing experiments because it can quickly provide information on the lifetime distributions by testing products or materials at higher than basic conditional levels of stress, such as pressure, temperature, vibration, voltage, or load to induce early failures. In this paper, a step stress partially accelerated life test (SS-PALT) is regarded under the progressive type-II censored data with random removals. The removals from the test are considered to have the binomial distribution. The life times of the testing items are assumed to follow length-biased weighted Lomax distribution. The maximum likelihood method is used for estimating the model parameters of length-biased weighted Lomax. The asymptotic confidence interval estimates of the model parameters are evaluated using the Fisher information matrix. The Bayesian estimators cannot be obtained in the explicit form, so the Markov chain Monte Carlo method is employed to address this problem, which ensures both obtaining the Bayesian estimates as well as constructing the credible interval of the involved parameters. The precision of the Bayesian estimates and the maximum likelihood estimates are compared by simulations. In addition, to compare the performance of the considered confidence intervals for different parameter values and sample sizes. The Bootstrap confidence intervals give more accurate results than the approximate confidence intervals since the lengths of the former are less than the lengths of latter, for different sample sizes, observed failures, and censoring schemes, in most cases. Also, the percentile Bootstrap confidence intervals give more accurate results than Bootstrap-t since the lengths of the former are less than the lengths of latter for different sample sizes, observed failures, and censoring schemes, in most cases. Further performance comparison is conducted by the experiments with real data.     

Gait Pattern Based on CMAC Neural Network for Robotic Applications

The main goal of this paper is to provide a general methodology and a practical approach for the design of gait pattern for biped robotic applications directly usable by researchers and engineers. This approach, which is based on CMAC neural network, is an alternative way in comparison to the traditional Central Pattern Generator. In the proposed method, the CMAC neural networks are used to learn basic motions (e.g. reference gait) and a Fuzzy Inference System allows to merge these reference motions in order to built more complex gaits. The results of our biped robotic applications show how to design a self-adaptive gait pattern according to average velocity and external perturbations.     

A Relative Representation of Trajectories in Geogaphical Spaces

The research presented in this paper introduces a relative representation of trajectories in space and time. The objective is to represent space the way it is perceived by a moving observer acting in the environment, and to provide a complementary view to the usual absolute vision of space. Trajectories are characterized from the perception of a moving observer where relative positions and relative velocities are the basic primitives. This allows for a formal identification of elementary trajectory configurations, and their relationships with the regions that compose the environment. The properties of the model are studied, including transitions and composition tables. These properties characterize trajectory transitions by the underlying processes that semantically qualify them. The approach provides a representation that might help the understanding of trajectory patterns in space and time.