A micromachined preconcentrator for ethylene monitoring system

The key component to enhance the sensitivity of the gas analysis system is the preconcentrator which accumulates, concentrates and releases the concentrated analyte upon applying a heating pulse. With increasingly strict regulations on the quality of fruits delivered to the consumer, maturity and ripening levels of fruits require very close monitoring of ethylene concentration. This paper focuses on the design, fabrication and characterization of a micromachined preconcentrator with an application emphasis on the monitoring of ethylene concentration. The device consists of 16 silicon microchannels loaded with carboxen 1000 adsorbent, a platinum microheater to heat the adsorbent to the desired operating temperature, and inlet/outlet fluidic ports. Thick silicon microchannels were etched using a DRIE process. Only clean air was used as a carrier and desorption gas. The enhancement of 100 ppb ethylene concentration was demonstrated. Various desorption flow rates as well as accumulation periods were tested.