Laser-Induced, Green and Biocompatible Paper-Based Devices for Circular Electronics

The growing usage and consumption of electronics-integrated items into the daily routine has raised concerns on the disposal and proper recycling of these components. Here, a fully sustainable and green technology for the fabrication of different electronics on fruit-waste derived paper substrate, is reported. The process relies on the carbonization of the topmost surface of different cellulose-based substrates, derived from apple-, kiwi-, and grape-based processes, by a CO2 laser. By optimizing the lasing parameters, electronic devices, such as capacitors, biosensors, and electrodes for food monitoring as well as heart and respiration activity analysis, are realized. Biocompatibility tests on fruit-based cellulose reveal no shortcoming for on-skin applications. The employment of such natural and plastic-free substrate allows twofold strategies for electronics recycling. As a first approach, device dissolution is achieved at room temperature within 40 days, revealing transient behavior in natural solution and leaving no harmful residuals. Alternatively, the cellulose-based electronics is reintroduced in nature, as possible support for plant seeding and growth or even soil amendment. These results demonstrate the realization of green, low-cost and circular electronics, with possible applications in smart agriculture and the Internet-of-Thing, with no waste creation and zero or even positive impact on the ecosystem

Game theory in mobile crowdsensing: A comprehensive survey

Mobile CrowdSensing (MCS) is an emerging paradigm in the distributed acquisition of smart city and Internet of Things (IoT) data. MCS requires large number of users to enable access to the built-in sensors in their mobile devices and share sensed data to ensure high value and high veracity of big sensed data. Improving user participation in MCS campaigns requires to boost users effectively, which is a key concern for the success of MCS platforms. As MCS builds on non-dedicated sensors, data trustworthiness cannot be guaranteed as every user attains an individual strategy to benefit from participation. At the same time, MCS platforms endeavor to acquire highly dependable crowd-sensed data at lower cost. This phenomenon introduces a game between users that form the participant pool, as well as between the participant pool and the MCS platform. Research on various game theoretic approaches aims to provide a stable solution to this problem. This article presents a comprehensive review of different game theoretic solutions that address the following issues in MCS such as sensing cost, quality of data, optimal price determination between data requesters and providers, and incentives. We propose a taxonomy of game theory-based solutions for MCS platforms in which problems are mainly formulated based on Stackelberg, Bayesian and Evolutionary games. We present the methods used by each game to reach an equilibrium where the solution for the problem ensures that every participant of the game is satisfied with their utility with no requirement of change in their strategies. The initial criterion to categorize the game theoretic solutions for MCS is based on co-operation and information available among participants whereas a participant could be either a requester or provider. Following a thorough qualitative comparison of the surveyed approaches, we provide insights concerning open areas and possible directions in this active field of research

Magnetization and stability study of a cobalt-ferrite-based ferrofluid

In this study the structural and magnetization properties of a CoFe2O4-based ferrofluid was investigated using x-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), Mössbauer spectroscopy, and magnetic Compton scattering (MCS) measurements. The XRD diagram indicates that the nanoparticles in the ferrofluid are inverse spinel and TEM graph shows that the ferrofluid consists of spherical nanoparticles with an average diameter of 18± 1 nm, in good agreement with the size, 19.4 nm, extracted from line broadening of the XRD peaks. According to EDS measurements the composition of the nanoparticles is CoFe2O4. Mössbauer spectroscopy shows that the cation distributions are (Co0.38Fe0.62)[Co0.62Fe1.38]O4. The MCS measurement, performed at 10 K, indicates that the magnetization of the nanoparticles is similar to magnetization of maghemite and magnetite. While the magnetization of the inverse spinels are in [111] direction, interestingly, the magnetization deduced from MCS is in [100] direction. The CoFe2O4-based ferrofluid is found to be stable at ambient conditions, which is important for applications

Sliding wear-induced chemical nanolayering in Cu–Ag, and its implications for high wear resistance

Sliding friction of metallic materials results in severe plastic deformation of the contacting surfaces. While plastic deformation is generally considered detrimental, as it leads to localized material failure and wear, in some cases it can trigger the formation of self-organized microstructures with the potential for improved wear resistance. We report here on a novel, self-adapting mechanism in a Cu90Ag10 two-phase alloy that relies on the spontaneous formation of chemically nanolayered structures during sliding wear. For sufficiently large initial Ag precipitate sizes, the nanolayered structures remain stable up to the sliding surface, leading to a reduction in wear rate. Similar chemically nanolayered structures are observed in Cu90Ag10 alloys deformed by high-pressure torsion, enabling controlled investigation of this process. The results of these studies suggest a novel approach, through self-organization, for designing metallic alloys that can achieve low wear rates. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

Forced chemical mixing of immiscible Ag-Cu heterointerfaces using high-pressure torsion

Forced chemical mixing in nanostructured Ag60Cu40 eutectic alloys during severe plastic deformation by high-pressure torsion (HPT) was quantitatively studied using x-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. Nearly complete chemical homogenization of the original lamellar structure with a wavelength of ≈ 165 nm was achieved after a shear strain of ≈ 350. The chemical mixing is accompanied by extensive grain refinement leading to nanocrystalline grains with average sizes of ≈ 42 nm. A Monte Carlo computer simulation model, which attributes mixing to dislocation glide, shows reasonable agreement with the experimental results. The model also shows that the characteristic strain for chemical homogenization scales linearly with the length scale of the system L, and not with the square of the length scale L2, as would be expected for Fickian diffusion

Microstructural evolution of nanolayered Cu–Nb composites subjected to high-pressure torsion

Bulk nanolayered Cu/Nb composites fabricated by accumulative roll bonding (ARB), leading to a nominal layer thickness of 18 nm, were subjected to large shear deformation by high-pressure torsion at room temperature. The evolution of the microstructure was characterized using X-ray diffraction, transmission electron microscopy and atom probe tomography. At shear strains of the crystallographic texture started to change from the one stabilized by ARB, with a Kurdjumov-Sachs orientation relationship and a dominant {1 1 2}(Cu)parallel to{1 1 2}(Nb) interface plane, toward textures unlike the shear texture of monolithic Cu and Nb. At larger strains, exceeding 10, the initial layered structure was progressively replaced by a three-dimensional Cu-Nb nanocomposite. This structure remained stable with respect to grain size, morphology and global texture from strains of similar to 290 to the largest ones used in this study, 5900. The three-dimensional self-organized nanocomposites comprised biconnected Cu-rich and Nb-rich regions, with a remarkably small coexistence length scale, similar to 10 nm. The results are discussed in the context of the effect of severe plastic deformation and strain path on microstructure and texture stability in highly immiscible alloy systems. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

Location Privacy-Preserving Mobile Crowd Sensing with Anonymous Reputation

In this paper, we give a location privacy-preserving solution for the mobile crowd sensing (MCS) system. The solution makes use of the blind signature technique for anonymous authentication and allows a mobile user to participate in the MCS for certain times set in the registration. Furthermore, we introduce a concept of anonymous reputation for mobile users on the basis of the blind signature technique as well. An anonymous reputation can be referred by the MCS platform when assigning tasks to a mobile user and can be upgraded or downgraded by the MCS platform, depending on the quality of reports submitted by the mobile user. For the security analysis, we provide security proofs for our solution on the basis of our formal definitions for anonymity, unlinkability and unforgeability for MCS. The performance analysis and experiments have shown that our solution is more efficient than existing solutions for MCS based on the blind signature technique

Location privacy-preserving mobile crowd sensing with anonymous reputation

In this paper, we give a location privacy-preserving solution for the mobile crowd sensing (MCS) system. The solution makes use of the blind signature technique for anonymous authentication and allows a mobile user to participate in the MCS for certain times set in the registration. Furthermore, we introduce a concept of anonymous reputation for mobile users on the basis of the blind signature technique as well. An anonymous reputation can be referred by the MCS platform when assigning tasks to a mobile user and can be upgraded or downgraded by the MCS platform, depending on the quality of reports submitted by the mobile user. For the security analysis, we provide security proofs for our solution on the basis of our formal definitions for anonymity, unlinkability and unforgeability for MCS. The performance analysis and experiments have shown that our solution is more efficient than existing solutions for MCS based on the blind signature technique.NRF (Natl Research Foundation, S’pore)Accepted versio