arXiv subjects

Jonathan Tan

Publications and source records attributed to Jonathan Tan.

5 recordsLinked to original sources

arXiv2026

Magnetoelectric Wireless Power Transfer Receivers for Sub-Millimeter Scale Implantable Bioelectronics

Implanted biomedical devices for continuous physiological monitoring require reliable wireless power delivery to anatomically constrained and sensitive sites where batteries are impractical or hazardous. Existing wireless power transfer (WPT) modalities, including inductive coils and ultrasonic transducers suffer from performance degradation as receiver dimensions are miniaturized, limiting their application for space-limited locations such as fingertips, the ocular cavity, and intracranial sites. We present a microelectromechanical systems (MEMS) magnetoelectric WPT receiver integrating piezoelectric aluminum scandium nitride and magnetostrictive iron-cobalt/silver multilayer thin-films, microfabricated within a footprint of 770 x 360 x 2.25 micrometers. The receiver operates at its 100 kHz flexural-mode resonance with a quality factor of 1180 and delivers 1.0 microwatt to a matched 10 kohm load under a standard-compliant 205 micro-Tesla RMS excitation field. This device exhibits a magnetoelectric coefficient of 1274 V cm-1 Oe-1 and a power figure of merit (FOMP) of 4.05 x 10-3 mW cm-3 Oe-2 Hz-1, both the highest reported values of comparable magnetoelectric WPT receivers. The FOM is 20-fold higher than the next best comparable-frequency device. These miniaturized devices establish MEMS magnetoelectric transduction as a scalable platform for battery-free wireless powering of microwatt-class implants in the most anatomically demanding regions of the body.

physics.app-ph↗

arXiv2025

A Galactic Interloper: A Study of the Cam OB1 Association's Clusters and its Visitor from the Perseus Arm

Within the molecular clouds of the Camelopardis OB1 association exists a region previously noted as one subgroup. However, bulk clustering from Gaia astrometry has recently shown three distinctive kinematically coherent groups, all found in a similar location in the sky ($137 \lessapprox l\lessapprox145$ and $-2\lessapprox b \lessapprox5$) and at a similar distance ($\sim$1kpc). In this work, we derive from first principles the three proposed clusters in this region, refine the membership list and cluster ages, and, for the first time, examine the 3D structure, motion, and origin of the clusters. Using clustering of Gaia data in 3D position + 2D velocity space, supplemented by available SDSS-V radial velocities, we find the clusters of ages 10, 15.8, and 20 Myr with members numbering 140, 469, and 184, respectively. All three clusters overlap currently in 3D space. Tracing their previous location, based on present-day motions, shows that each cluster originated in its own distinct region and exhibited no influence on each other's formation. Two of the clusters trace their origin to different areas within the Cam OB1 association, with the oldest cluster tracing its origins to the near edge of the Perseus arm, in the direction of the Per OB1 or Cas 0B6 associations. Overall, this work illustrates how different stellar groups, even those originating in a different spiral arm, can visit and pass through each other as they travel through the Galaxy.

astro-ph.GA↗

arXiv2025

Leakage Suppression Across Temperature in Al1-xScxN Thin Film Ferroelectric Capacitors through Boron Incorporation

This paper presents high-temperature ferroelectric characterization of 40~nm Al$_{1-x-y}$B$_x$Sc$_y$N (AlBScN) thin film capacitors grown by co-sputtering Al$_{0.89}$B$_{0.11}$ and Sc targets onto Pt(111)/Ti(002)/Si(100) substrates. Structural analysis confirmed a c-axis-oriented wurtzite structure with a low surface roughness of 1.37~nm. Ferroelectric switching, characterized by positive-up-negative-down (PUND) measurements up to 600~$^\circ$C, exhibited a linear decrease in coercive fields from 6.2~MV/cm at room temperature to 4.2~MV/cm at 600~$^\circ$C, while remanent polarization remained stable with temperature. Direct current I-V measurements highlight a significant suppression of leakage currents, over two orders of magnitude lower compared to AlScN capacitors fabricated under similar conditions. These results position AlBScN thin films as strong candidates for ferroelectric applications in extreme environments.

cond-mat.mtrl-sci↗

arXiv2021

Ariel: Enabling planetary science across light-years

Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, was adopted as the fourth medium-class mission in ESA's Cosmic Vision programme to be launched in 2029. During its 4-year mission, Ariel will study what exoplanets are made of, how they formed and how they evolve, by surveying a diverse sample of about 1000 extrasolar planets, simultaneously in visible and infrared wavelengths. It is the first mission dedicated to measuring the chemical composition and thermal structures of hundreds of transiting exoplanets, enabling planetary science far beyond the boundaries of the Solar System. The payload consists of an off-axis Cassegrain telescope (primary mirror 1100 mm x 730 mm ellipse) and two separate instruments (FGS and AIRS) covering simultaneously 0.5-7.8 micron spectral range. The satellite is best placed into an L2 orbit to maximise the thermal stability and the field of regard. The payload module is passively cooled via a series of V-Groove radiators; the detectors for the AIRS are the only items that require active cooling via an active Ne JT cooler. The Ariel payload is developed by a consortium of more than 50 institutes from 16 ESA countries, which include the UK, France, Italy, Belgium, Poland, Spain, Austria, Denmark, Ireland, Portugal, Czech Republic, Hungary, the Netherlands, Sweden, Norway, Estonia, and a NASA contribution.

astro-ph.IM↗

arXiv2013

Millimetre-Wave and Near-Infrared Signposts of Massive Molecular Clump Evolution and Star Cluster Formation

We report new near-infrared and mm-wave observational data on a selection of massive Galactic molecular clumps (part of the CHaMP sample) and their associated young star clusters. The clumps show, for the first time in a "dense gas tracer", a significant correlation between HCO+ line emission from cold molecular gas and Brγ line emission of associated nebulae. This correlation arises in the HCO+ line's brightness, not its linewidth. In contrast, the correlation between the N2H+ line emission and Brγ is weak or absent. The HCO+/N2H+ line ratio also varies widely from clump to clump: bright HCO+ emission tends to be more closely associated with Brγ nebulosity, while bright N2H+ emission tends to avoid areas that are bright in Brγ. Both molecular species show correlations of weak significance with infrared H2 v=1-0 and v=2-1 line emission, in or near the clumps. The H2 emission line ratio is consistent with fluorescent excitation in most of the clumps, although thermal excitation is seen in a few clumps. We interpret these trends as evidence for evolution in the gas conditions due to the effects of ongoing star formation in the clumps, in particular, the importance of UV radiation from massive YSOs as the driving agent that heats the molecular gas and alters its chemistry. This suggests that some traditional dense gas tracers of molecular clouds do not sample a homogeneous population of clumps, i.e., that the HCO+ brightness in particular is directly related to the heating and disruption of cold gas by massive young stars, whereas the N2H+ better samples gas not yet affected by this process. We therefore suggest that the HCO+-N2H+-Brγ relationship is a useful diagnostic of a molecular clump's progress in forming massive stars.

astro-ph.GA↗