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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
NASA NTRS2022

Reversible Colorimetric Sensing of Volatile Analytes By Wicking in Close Proximity to A Photonic Film

Isolation of volatile analytes from environmental or biological fluids is a rate-determining step that can delay the response time for continuous sensing. In this paper, we demonstrate a colorimetric sensing system that enables the rapid detection of gas-phase analytes released from a flowing micro-volume fluid sample. The sensor platform is an analyte-responsive metal-insulator-metal (MIM) thin-film structure integrated with a large area quartz micropillar array. This allows precise planar alignment and microscale separation (310 μm) of the optical and fluidic structures. This configuration offers rapid and homogeneous color changes over large areas that permits detection by low-resolution optics or eye, which is well-suited to portable/wearable devices. For our proof-of-principle demonstration, we utilized a poly(methyl methacrylate) (PMMA) spacer and evaluated the sensor's response (color change) to ethanol vapor. We show that the RGB color value is quantitatively linked to the spacer swelling, which is reversible and repeatable. The optofluidic platform reduces the sensor response time from minutes to seconds compared with experiments using a conventional chamber. The sensor's concentration-dependent response was examined, confirming the potential of the reported sensing platform for continuous, compact, and quantitative colorimetric analysis of volatile analytes in low-volume samples, such as biofluids.

Timothy J. Palinski↗
DOE OSTI2013

Proximity charge sensing for semiconductor detectors

A non-contact charge sensor includes a semiconductor detector having a first surface and an opposing second surface. The detector includes a high resistivity electrode layer on the first surface and a low resistivity electrode on the high resistivity electrode layer. A portion of the low resistivity first surface electrode is deleted to expose the high resistivity electrode layer in a portion of the area. A low resistivity electrode layer is disposed on the second surface of the semiconductor detector. A voltage applied between the first surface low resistivity electrode and the second surface low resistivity electrode causes a free charge to drift toward the first or second surface according to a polarity of the free charge and the voltage. A charge sensitive preamplifier coupled to a non-contact electrode disposed at a distance from the exposed high resistivity electrode layer outputs a signal in response to movement of free charge within the detector.

47 OTHER INSTRUMENTATION↗
DOE OSTI2013

Within a Stone's Throw: Proximal Geolocation of Internet Users via Covert Wireless Signaling

While Internet users may often believe they have anonymity online, a culmination of technologies and recent research may allow an adversary to precisely locate an online user s geophysical location. In many cases, such as peer-to-peer applications, an adversary can easily use a target s IP address to quickly obtain the general geographical location of the target. Recent research has scoped this general area to a 690m (0.43 mile) radius circle. In this work, we show how an adversary can exploit Internet communication for geophysical location by embedding covert signals in communication with a target on a remote wireless local area network. We evaluated the approach in two common real-world settings: a residential neighborhood and an apartment building. In the neighborhood case, we used a single-blind trial in which an observer located a target network to within three houses in less than 40 minutes. Directional antennas may have allowed even more precise geolocation. This approach had only a 0.38% false positive rate, despite 24,000 observed unrelated packets and many unrelated networks. This low rate allowed the observer to exclude false locations and continue searching for the target. Our results enable law enforcement or copyright holders to quickly locate online Internet users without requiring time-consuming subpoenas to Internet Service Providers. Other privacy use cases include rapidly locating individuals based on their online speech or interests. We hope to raise awareness of these issues and to spur discussion on privacy and geolocating techniques.

geolocation↗
DOE OSTI2016

Atmospheric pressure plasma processing of polymeric materials utilizing close proximity indirect exposure

A plasma treatment method that includes providing treatment chamber including an intermediate heating volume and an interior treatment volume. The interior treatment volume contains an electrode assembly for generating a plasma and the intermediate heating volume heats the interior treatment volume. A work piece is traversed through the treatment chamber. A process gas is introduced to the interior treatment volume of the treatment chamber. A plasma is formed with the electrode assembly from the process gas, wherein a reactive species of the plasma is accelerated towards the fiber tow by flow vortices produced in the interior treatment volume by the electrode assembly.

36 MATERIALS SCIENCE↗