Integrated chemiresistor array for small sensor platforms

Abstract

Chemiresistorsare fabricatedfrom materialsthat changetheir electricalresistancewhen exposedto certain chemical species.Composites of soluble polymers with metallic particles have shown remarkable sensitivity to many volatile organic chemicals, depending on the ability of the rmalyte molecules to swell the polymer matrix. These sensors can be made extremely small (< 100 square microns), operate at ambient temperatures, and require almost no power to read-out. However, the chemiresistor itself is only a part of a more complex sensor system that delivers chemical information to a user who can act on the information. We present the design, fabrication and performance of a chemiresistor array chip with four different chemiresistor materials, heaters and a temperature sensor. We also show the design and fabrication of an integrated chemiresistor array, where the electronics to read-out the chemiresistors is on the same chip with the electrodes for the chemiresistors. The circuit was designed to perform several fi,mctions to make the sensor data more usefi,d. This low-power, integrated chemiresistor array is small enough to be deployed on a Sandia-developed microrobot platform.

Review of Chemical Sensors for In-Situ Monitoring of Volatile Contaminants

“…The Sandia sensor-array chip has several advantages over the Adsistor™: 1) an array of differing sensors can be used to identify different VOCs; a single Adsistor cannot; 2) the footprint of a cylinder is not conducive to temperature control and measurement like the Sandia chip, which is also much smaller; 3) the fact that we control our own formulations is important for understanding how to improve performance through better processing; and 4) our chip geometry and preconcentrator design allows us to look for improvements in sensitivity in an integrated MEMs produced package. See Hughes et al (2000) for more details of the Sandia chemiresistor array. …”

Sensors for environmental monitoring and long-term environmental stewardship.

“…The amount of swelling corresponds to the concentration of the chemical vapor in contact with the chemiresistor, so these devices can be calibrated by exposing the chemiresistors to known concentrations of target analytes. Figure 5 shows the architecture of the microsensor, which integrates an array of chemiresistors with a temperature sensor and heating elements (Hughes et al, 2000). The chemiresistor array has been shown to detect a variety of VOCs including aromatic hydrocarbons (e.g., benzene), chlorinated solvents (e.g., trichloroethylene (TCE), carbon tetrachloride), aliphatic hydrocarbons (e.g., hexane, iso-octane), alcohols, and ketones (e.g., acetone).…”

In-Situ Chemiresistor Sensor Package for Real-Time Detection of Volatile Organic Compounds in Soil and Groundwater

“…First, the architecture of the microsensor integrates an array of chemiresistors with a temperature sensor and heating elements (Figure 2) [6]. The array of differing sensors can be used to identify different VOCs by comparing the resulting chemical signatures with calibration (or training) sets and pattern-recognition methods [7][8][9][10][11][12].…”