This is the basis of a smart key for automobiles that cannot be driven until somebody's breath has been tested for alcohol. If that test is failed then the car can be locked not to start.
The sensor is an oxide insulator sandwiched between the electrodes. The water vapor from the breath is adsorbed on the insulator and then an electric current flows between the electrodes. The ethanol concentration is measured by three sensors tuned to detect ethanol, metabolized acetaldehyde in breath after drinking, and hydrogen, respectively. This method improves accuracy by about a factor of three compared with those that use only an ethanol sensor for measurement. Also, the device is capable of measuring an ethanol concentration of 0.015 mg/L compared to 0.15 mg/L of the alcohol which constitutes being "under the influence of alcohol" and a charge of drunk driving in Japan.
Other developments within the sensor include micrometer-scale comb-shaped electrodes used to improve the sensitivity of the sensor. This enables the device to detect a tiny amount of saturated water vapour with a modest sensor area of 5 square millimeters. This reduces size and power consumption allowing the breathalyser to be put in a smart key and battery operated.
The device has been designed to be tamper-proof and can detect the saturated water vapor from human breath and accurately measure alcohol level within 3 seconds once a driver exhales breath onto the device.
Such keys may become mandatory in some markets. In the U.S., the National Highway Traffic Safety Administration (NHTSA) has asked for the development of ignition interlock technology that connects alcohol detectors to a vehicle’s engine.
Hitachi and Honda are aiming to commercialize this developed technology through effectively collecting data from future validation tests. The prototype is due to be presented at the SAE 2016 World Congress and Exhibit, which will be held in Detroit, Michigan.
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