2003 Progress Report: Low Cost Organic Gas Sensors on Plastic for Distributed Environmental MonitoringEPA Grant Number: R830899
Title: Low Cost Organic Gas Sensors on Plastic for Distributed Environmental Monitoring
Investigators: Subramanian, Vivek
Institution: University of California - Berkeley
EPA Project Officer: Carleton, James N
Project Period: May 1, 2003 through April 30, 2006
Project Period Covered by this Report: May 1, 2003 through April 30, 2004
Project Amount: $328,000
RFA: Environmental Futures Research in Nanoscale Science Engineering and Technology (2002) RFA Text | Recipients Lists
Research Category: Nanotechnology , Safer Chemicals
The overall objective of this research project is to develop novel arrayed gas sensors on plastic that offer extremely high specificity and broad-range detection capability while maintaining low fabrication cost, making them viable for use in distributed environmental monitoring applications, where cost is an important criterion.
In Year 1 of the project, we successfully developed a baseline sensor technology and used it to detect numerous common organic environmental contaminants, including various alcohols, ketones, and other solvents often found in industrial waste.
The sensor technology that we have implemented to this point has made use of solution-processed organic semiconductors deposited on a common gate structure to form arrays of organic transistors. The use of a common gate process allows us to rapidly prototype devices, reducing learning cycle time. Importantly, in these devices, the channel layer of the transistor is exposed to the environment. By using appropriate channel materials, it is possible to demonstrate sensing functionality for various fluids. We have developed organic sensors using several different organic semiconductors, including several polythiophenes and pentacene derivatives. These have been used to achieve sensing of several organic environmental contaminants. Studies also have been performed on the cycle-life of these sensors, and qualitative models for sensor operation also have been identified. Failure mechanisms related to sensor poisoning have been identified, and attempts to overcome these are underway.
To facilitate accurate sensor characterization, a robust sensor testing facility has been constructed. This system uses multiple mass-flow controllers and meters to inject controlled amounts of analyte and/or mixtures of analytes into a sensor test chamber. The chamber includes electrical I/O connections to enable real-time measurements on the sensor arrays. Sensing of liquid vapors also is possible using a bubbler. Using this methodology, we have been able to study the transient response of organic transistor gas sensors for the first time.
We have focused on developing the baseline sensor technology on a common gate. The use of a common gate prevents true arrayed operation because all transistors on a substrate are addressed simultaneously. This limits the viability of these sensors because they individually have poor specificity. To achieve specificity, it will be necessary to demonstrate true arrayed operation. In Year 2 of this research project, we will continue to develop the technology to facilitate this by demonstrating true arrayed operation using individually gated devices. These then will be deployed to attempt realistic testing of environmental contaminants.