arXiv subjects

Yuning Zhang

Publications and source records attributed to Yuning Zhang.

58 records · Page 4Linked to original sources

arXiv2018

From 2D to 3D: graphene moulding for transparent and flexible probes

Chemical vapor deposition (CVD) has been widely adopted as the most scalable method to obtain single layer graphene. Incorporating CVD graphene in planar devices can be performed via well established wet transfer methods or thermal adhesive release. Nevertheless, for applications involving 3D shapes, methods adopted for planar surface provide only a crude solution if a continuous, tear-free, wrinkle-free graphene layer is required. In this work, we present the fabrication and characterization of PDMS-supported 3D graphene probes. To accommodate 3D geometries, we perform CVD on catalysts possessing a non-trivial 3D topology, serving to mold the grown graphene to a final non-trivial 3D shape. This advance overcomes challenges observed in standard transfer processes that can result in uneven coverage, wrinkles and tears. To demonstrate the potential of our new transfer approach, we apply it to fabricate graphene electrical probes. Graphene, due to its flexibility, transparency and conductivity, is an ideal material with which to replace conventional metal based probes. In particular, with a contact resistance in the order of tens of kOhm, these graphene probes may find applications, such as in electrophysiology studies.

cond-mat.mtrl-sci↗

arXiv2017

Unsupervised Motion Artifact Detection in Wrist-Measured Electrodermal Activity Data

One of the main benefits of a wrist-worn computer is its ability to collect a variety of physiological data in a minimally intrusive manner. Among these data, electrodermal activity (EDA) is readily collected and provides a window into a person's emotional and sympathetic responses. EDA data collected using a wearable wristband are easily influenced by motion artifacts (MAs) that may significantly distort the data and degrade the quality of analyses performed on the data if not identified and removed. Prior work has demonstrated that MAs can be successfully detected using supervised machine learning algorithms on a small data set collected in a lab setting. In this paper, we demonstrate that unsupervised learning algorithms perform competitively with supervised algorithms for detecting MAs on EDA data collected in both a lab-based setting and a real-world setting comprising about 23 hours of data. We also find, somewhat surprisingly, that incorporating accelerometer data as well as EDA improves detection accuracy only slightly for supervised algorithms and significantly degrades the accuracy of unsupervised algorithms.

cs.HC↗

arXiv2015

Dynamic Imaging of Au-nanoparticles via Scanning Electron Microscopy in a Graphene Wet Cell

High resolution nanoscale imaging in liquid environments is crucial for studying molecular interactions in biological and chemical systems. In particular, electron microscopy is the gold-standard tool for nanoscale imaging, but its high-vacuum requirements make application to in-liquid samples extremely challenging. Here we present a new graphene based wet cell device where high resolution SEM (scanning electron microscope) and Energy Dispersive X-rays (EDX) analysis can be performed directly inside a liquid environment. Graphene is an ideal membrane material as its high transparancy, conductivity and mechanical strength can support the high vacuum and grounding requirements of a SEM while enabling maximal resolution and signal. In particular, we obtain high resolution (< 5 nm) SEM video images of nanoparticles undergoing brownian motion inside the graphene wet cell and EDX analysis of nanoparticle composition in the liquid enviornment. Our obtained resolution surpasses current conventional silicon nitride devices imaged in both SEM and TEM under much higher electron doses.

cond-mat.soft↗

arXiv2015

Rayleigh scattering and depolarization ratio in linear alkylbenzene

Linear alkylbenzene (LAB) is adopted to be the organic solvent for the Jiangmen Underground Neutrino Observatory (JUNO) liquid scintillator detectors due to the ultra-transparency. However the current Rayleigh scattering length calculation disagrees with the measurement. The present paper for the first time reports the Rayleigh scattering of LAB being anisotropic and the depolarization ratio being 0.31+-0.01(stat.)+-0.01(sys.). We proposed an indirectly method for Rayleigh scattering measurement with Einstein-Smoluchowski-Cabannes formula, and the Rayleigh scattering length of LAB is determined to be 28.2+-1.0 m at 430 nm.

physics.ins-det↗