Design and Fabrication of a Micropreconcentrator Focuser for Sensitivity Enhancement of Chemical Sensing Systems

The low sensitivity of the gas monitoring system, especially in low concentration range, can be overcome by a miniaturized-based preconcentrator focuser, which can be integrated at the front end of the system. The preconcentrator focuser accumulates, concentrates, and releases the concentrated target analyte upon applying a heating pulse, thus extensively enhancing the sensitivity of the system. Recently, highly strict regulations on the quality of fruits have been applied to deliver high quality fruits to the consumer. Therefore, precise monitoring of ethylene as a ripeness accelerator to the fruits is very important. This paper presents the design, fabrication, and characterization of micropreconcentrator focuser for ethylene monitoring. The device is based on silicon microtrenches that serve as a microheater and microchannels loaded with Carboxen 1000 adsorbents. Thick silicon microtrenches are formed using deep reactive ion etching process. The silicon structures are sandwiched between two Pyrex wafers by anodic bonding. Only clean air is used as a carrier and desorption gas. The enhancement of 100-ppb ethylene concentration is discussed and presented. The device performance for various operations parameters is demonstrated.