arXiv subjects

Luca Selmi

Publications and source records attributed to Luca Selmi.

3 recordsLinked to original sources

arXiv2026

Uphill transport in competitive drift-diffusion models with volume exclusion

This paper addresses uphill transport (defined as a regime in which particle flow is opposite to the prescriptions of Fick's diffusion) in drift-diffusion particle transport constrained by volume exclusion. Firstly, we show that the stationary hydrodynamic limit of a multispecies, weakly asymmetric exclusion process (SHDL) naturally predicts precisely characterized uphill regimes in the space of external drivings. Then, with specific reference to systems of oppositely charged particles, we identify well-defined model hypotheses and extensions whereby the SHDL converges to the modified Poisson-Nernst-Planck model, thus bridging the gap between exclusion-based particle models and continuum descriptions commonly used in engineering. The merits and limitations of the models in describing the particle fluxes and predicting uphill transport conditions are investigated in detail with respect to the adopted approximations and simplifications. The results demonstrate the persistence of uphill transport phenomena across modeling scales, clarify the conditions under which they occur, and suggest that uphill transport may play a significant role in nanoscale electrolytes, confined ionic and iontronic devices, and membrane-based technologies.

cond-mat.stat-mech↗

arXiv2025

Bio-integrated ${\mu}$Bots with Overtone Ultra-Wideband Magnetoelectric Antennas for Wireless Telemetry

Implantable and wearable devices require antennas that are both miniaturized and efficient, yet conventional designs are constrained by narrow bandwidth and orientation sensitivity. We report overtone ultra-wideband magnetoelectric (OUWB-ME) antennas that exploit higher order acoustic modes in polished silicon substrates to achieve a 22.6 GHz bandwidth in the 3-4 GHz range. Packaged into "${\mu}$Bots," these magnetoelectric heterostructures bonded with silver nanoparticle inks maintain stable operation under biological loading. In vitro assays confirm the biocompatibility of AlN and the protective role of parylene encapsulation for FeGa. Ex vivo rat and human tissues reshape transmission spectra, identifying reproducible frequency windows near 3.3 and 3.9 GHz. ${\mu}$Bots enable real-time audiovisual telemetry using software-defined radios and exhibit compatibility with 7T MRI. By combining wideband response, robustness to misalignment, and biocompatible packaging, OUWB-ME ${\mu}$Bots provide a scalable platform for wireless bio-integrated communication and telemetry.

physics.app-ph↗

arXiv2020

Dependable contact related parameter extraction in graphene-metal junctions

The accurate extraction and the reliable, repeatable reduction of graphene - metal contact resistance (R$_{C}$) are still open issues in graphene technology. Here, we demonstrate the importance of following clear protocols when extracting R$_{C}$ using the transfer length method (TLM). We use the example of back-gated graphene TLM structures with nickel contacts, a complementary metal oxide semiconductor compatible metal. The accurate extraction of R$_{C}$ is significantly affected by generally observable Dirac voltage shifts with increasing channel lengths in ambient conditions. R$_{C}$ is generally a function of the carrier density in graphene. Hence, the position of the Fermi level and the gate voltage impact the extraction of R$_{C}$. Measurements in high vacuum, on the other hand, result in dependable extraction of R$_{C}$ as a function of gate voltage owing to minimal spread in Dirac voltages. We further assess the accurate measurement and extraction of important parameters like contact-end resistance, transfer length, sheet resistance of graphene under the metal contact and specific contact resistivity as a function of the back-gate voltage. The presented methodology has also been applied to devices with gold and copper contacts, with similar conclusions.

physics.app-ph↗