Fully autonomous gas sensor device

First proof-of-concept of a fully autonomous gas sensor device based on nanotechnology. The sensor consists of just one single nanowire of sno2, The thermal inertia of this small piece of material is so low that it can be operated with ONLY few tens of microwatts. Such a low amount of power can just be obtained from the ambience with current energy harvesting technologies. (1) The system is powered with a thermoelectric energy harvesting microgenerator. As soon as this generator is warmed up with the heat from the human body, the system turns on (0:03s) (2) Human breath contains water, CO2 and many other compouns that can be detected with sno2. Thus, the sensor displays a significant response when exposed to exhaled air. (0:09s) (3) After removeing the heat source (the hand is not in touch with the device anymore), the generator switches off in a few seconds (0:29s). Details about the authorship of this work can be found elsewhere: dx.doi.org Note: The cord only reads the signal from the device. No additional power is supplied.

Nanothermal trumpet: thermoacoustic sound source made with a suspended metal nanowire

From the paper “Suspended metal wire array as a thermoacoustic sound source,” Appl. Phys. Lett. 95, 163102 (2009); by AO Niskanen, J. Hassel, M. Tikander, P. Maijala, L. Grönberg, P. Helistö, from VTT Technical Research Centre of Finland, PO BOX 1000, 02044 VTT, Finland. dx.doi.org A suspended metal wire array is used to produce high-pressure sound waves over a wide spectrum using the thermoacoustic effect. It is fabricated with an air-bridge arrays containing up to 2×105 wires covering an area of a few square centimeters. The supporting silicon wafer was isotropically plasma etched to release the wires thereby avoiding heat contact with the substrate. Sound pressure levels reaching 110 db at a distance of 8 cm were demonstrated near 40 khz in free field. The devices are also able to reproduce music and speech. They have potential for applications especially in the ultrasound range.