Mid Sweden University

Time-varying electric fields induce displacement currents through capacitive coupling, resulting in current continuity even in the absence of conduction paths. While capacitive coupling is known as a parasitic effect, its role in directly activating solid-state devices in open circuits remains underexplored. Here, we demonstrate that externally generated, time-varying electric fields—produced by triboelectric excitation or moving charged objects—can directly activate linear and nonlinear components, such as diodes, rectifiers, and LEDs, without a galvanic connection. A lumped-element capacitive-coupling model captures the observed dependencies Vab∝ω and Vab∝1/r, validated experimentally on both linear and non-linear components. The resulting field-driven activation enables energy harvesting in open circuits, multi-channel control, and wireless sensing of human motion and mechanical vibrations over meter-scale distances. This quasi-static capacitive coupling operates in a distinct regime compared to resonant wireless power transfer, because it is drive by low-frequency, motion induced electric field changes that generate transient displacement currents in floating circuits. The findings here enable contact-free activation of electronic components through discrete energy transfer rather than traditional continuous power delivery.

Silicon-based anodes offer substantially higher theoretical capacities than graphite in lithium-ion batteries, but their practical deployment is hindered by severe volume changes that induce mechanical degradation and unstable interfacial chemistry. While nanoscaling strategies can mitigate these effects, they often suffer from low tapped density, complex synthesis, and limited scalability. Porous silicon microparticles provide a promising alternative by partially accommodating volume expansion while preserving processability and electrode-level integrity. Here, a HF-free urea-assisted etching strategy is employed to generate porous silicon microparticles under mild conditions, leveraging the coupled action of thermally induced structural disruption and chemically driven surface modification. Control experiments confirm that the combined action of these effects is essential to achieve BJH-resolved mesoporosity and increased surface area. The resulting porous silicon exhibits oxygen- and nitrogen-containing surface functionalities. Composite electrodes prepared with nanographite and sodium alginate binder at graphite:silicon:binder ratios of 8:1:1, 7:2:1, and 4.5:4.5:1 demonstrate improved electrochemical behavior. In half-cell testing, electrodes containing 10-20 wt % porous silicon deliver stable redox activity and retain 630-880 mAh g-1 after 100 cycles at 0.1 C, with Coulombic efficiencies of 98.8-99.7%, whereas higher silicon loadings lead to rapid capacity decay. Cycling-resolved impedance and differential-capacity analyses reveal the formation of a thicker yet mechanically resilient interphase that stabilizes charge-transfer kinetics, while rate capability tests show 65-74% capacity retention at 2 C.

Silicon materials are currently being explored for usage in lithium–ion battery anodes due to their high lithium storage capacity,but their practical application is hindered by severe volume expansion during cycling, leading to mechanical degradation andcapacity fading. This study introduces a novel two-pot method for synthesizing silicon nanoparticles (Si NPs) to address thesechallenges. The method decouples precursor decomposition and nanoparticles deposition enabling in situ growth of Si NPs onnanographite substrates. By replacing hazardous silane precursors with polyvinyl alcohol or hydrogen gas, we eliminate safetyrisks while simplifying production. Scanning electron microscopy and electrochemical characterization confirm uniform Si NPdeposition. The fabricated electrodes displayed stable electrochemical performance with a capacity of 503 mAh/g after 100 cyclesin a half-cell configuration. This approach offers a safe route for producing high-performance silicon-based anodes.

Triboelectric nanogenerators (TENGs) represent a promising technology for energy harvesting and self-powered sensing with a wide range of applications. Despite their potential, challenges such as the need for cost-effective, large-area electrodes and engineering sustainable triboelectric materials remain, especially given the impending restrictions on single-use engineering plastics in Europe. To address these challenges, engineering nano-graphite-coated paper is presented as a sustainable and high-performance alternative for triboelectric layers. Moreover, this material, which can be produced on an industrial scale, offers a viable replacement for metal electrodes. The combination of nano-graphite and paper, with its large contact area and inherent surface roughness, enables ultra-high power densities exceeding 14 kW m−2, driven by electrostatic discharge at the surface. Beyond energy harvesting, smart sensors are developed for floors and walls that detect movements for security purposes and smart sheets that monitor body movements and physiological activities during sleep. The findings highlight the potential of this engineering paper to serve as an eco-friendly alternative to engineering plastics in TENGs and electrodes, opening new avenues for future applications. 

Harvesting energy from distributed mechanical motions has garnered significance in future power sources for small electronics and sensors. Although technologies like triboelectric nanogenerators have shown promising results, their efficacy hinges on the alignment of motion vectors and device architectures. Here, an approach employing stationary diode cells (DiCes) to generate electricity is presented. This approach leverages dynamically changing electrostatic fields to induce potential differences across diode junctions via electrostatic induction, which is verified theoretically and experimentally. DiCes constructed with multiple diodes can directly output DC voltage and current. A 0.02 m2 sized DiCe contains 360 diodes can supply a DC voltage and current of maximum 490 V and 1.08 mA, respectively, which equals a DC power density of 26.5 W<middle dot>m-2. Capable of functioning in both contact and non-contact modes, DiCes offer versatile applications, from wirelessly powering implanted medical devices to harvesting energy from vehicles and roads.

Silicon materials are currently being explored for usage in lithium-ion battery anodes due to their high lithium storage capacity. We have developed a novel method, using a simple thermal treatment of low-cost silicon powder and nanographite, resulting in a composite where silicon nanoparticles are grown on the graphene surfaces. Electrodes fabricated from these Si-NG composites delivered a stable capacity of 489 mAh/g during 25 cycles, i.e. higher than conventional graphite anodes (theoretical capacity: 372 mAh/g). The method uses low-cost materials and avoids complex setups, thereby suggesting industrial scalability.

Porous silicon (Si) has gained significant interest in various applications due to its high surface area, tunable pore structure, excellent chemical reactivity, biocompatibility, and surface functionalization potential. Traditional methods for synthesizing porous Si often rely on hydrofluoric acid, a hazardous chemical that poses significant environmental and safety risks, limiting its scalability and sustainability. In this study, a green and scalable approach for synthesizing porous Si microparticles through urea-assisted etching is presented and evaluated as a function of temperature and container conditions (crucible vs. autoclave). The urea etching transformed pristine silicon microparticles, with a non-porous structure and a BET surface area of 2.3 m2/g, into porous silicon with surface areas as high as 26.7 m2/g. The highest porosity was achieved at 400 °C, while higher temperatures (600 °C and 800 °C) led to diminished porosity and surface restructuring. Quantitative analysis revealed a maximum etching yield of 17.5 %, etching rate of 14.6 mg/h, and a pore formation efficiency of ∼43 %. The crystalline structure of silicon remained intact across all treatments, with minor surface disorder observed at higher temperatures. The urea-assisted etching produced a temperature-and environment-dependent surface oxidation and nitrogen incorporation. At 220 °C and 400 °C, a thick oxide layer formed, particularly under high-‍pressure conditions, while oxidation was less pronounced at 600 °C and 800 °C, likely due to rapid thermal decomposition limiting sustained gas-solid interactions. Nitrogen incorporation was most significant in Si-220-HP, where multiple nitrogen environments were detected, including Si–N, NH2/NH3+, and NOx species. At higher temperatures, only stable Si–N bonds persisted, while other nitrogen species diminished. 

This paper reports the design and numerical results of three new extremely compact and efficient flat-top band-pass plasmonic filters operating in the near-infrared region. The proposed structures are realized in metal–insulator-metal plasmonic waveguides based on stub, tilted T-junction and right-angle trapezoid configurations. A built-in parameterized genetic algorithm is applied to maximize the transmission efficiency, while at the same time contributing to shrinking down the size of the device structures. It is shown that the tunability of the optical filters can be realized by modulating their structural parameters to gain control over the band-pass filtering wavelengths. Numerical calculations are conducted based on the finite element method of CST Microwave Studio and demonstrate that the suggested ultra-compact plasmonic waveguide filters offer wide bandwidths of more than 270 nm, 424 nm, and 289 nm, with transmission efficiencies of higher than 80%, 74.2%, and 74.3%, respectively. The sizes of the proposed wavelength filters are 490 nm × 575 nm, 350 nm × 180 nm, and 420 nm × 150 nm, respectively, which make them attractive candidates for applications in high density photonic integrated circuits (PICs). As a result, because of the promising characteristics of the proposed topologies such as their high efficiency, compact size, tunability, and simple structure they may find applications in on-chip integration, laser technology, and multi-photon fluorescence. 

Additive manufacturing is rapidly growing, where selective laser sintering technology dominates for industrial use. In the case of polymer selective laser sintering, polyamide is the standard material. However, polyamide is an electrical insulator, and for specific applications, it would be desirable to be able to manufacture polymer-based electrically conductive parts. Electromagnetic Compatibility is one of the most significant targeted applications, where the introduction of electric vehicles raises new electromagnetic compatibility demands. The goal is, therefore, to develop an electrically conductive composite material for selective laser sintering using graphene as the additive. Composites are prepared by mixing polyamide, graphene, and additives with varying graphene/polyamide ratios. The aim of this investigation is the laser-assisted processing of the resulting graphene/polyamide composites with various parameters to sinter the material, forming a solid conductive structure. The structure is characterized using SEM and resistance measurements. Results show sheet resistance values of about 700Ω/sq after laser-assisted processing with good powder flowability. 

The 99.99% Al used for negative Al electrodes in aluminum-based battery studies is expensive. This is primarily due to the complex challenges associated with fabricating 99.99% Al, particularly the removal of Fe impurities from Al melts. Despite the importance of this issue for the future commercialization of Al-based batteries, it has been largely overlooked. This work accordingly studied the plating/stripping behavior of Al containing 1 wt % iron (Al 1% Fe) as an alternative electrode using conventional ([EMIm]Cl and AlCl3) electrolyte. Simultaneously, the impact of the surface microstructure of Al 1% Fe on the plating/stripping behavior was examined. The results indicate that the difference in the plating/stripping cycling of Al 1% Fe alloys and 99.99% Al is negligible. Thus, Al 1% Fe negative electrodes could serve as an efficient and commercially viable alternative to 99.99% Al for plating/stripping in Al-based batteries. This is an essential finding because facile and commercial fabrication of Al 1% Fe electrodes is absolutely feasible. The results are further discussed in terms of the impact of the Al surface microstructure (i.e., grain size, defect density, grain boundary distribution, crystal orientation, and intermetallic phases) on plating/stripping behavior. Moreover, this study provides insights into how the interphase layer formed on Al electrodes influences plating/stripping behavior.