Invited Paper NS+EM+EN-TuM5
Nano-enabled Chemical, Bio and Radiation Sensors

Tuesday, October 29, 2013, 9:20 am, Room 203 B

We have been pursuing development of chemical and biosensors using CNTs for the last several years and this talk will present our progress to date. In the case of chemical sensors, we use an interdigitated electrode as a chemiresistor, where purified SWCNTs serve as the conducting medium. When the chemiresistor is exposed to a gas or vapor, the change in resistance is recorded; if SWCNTs do not respond to a particular gas or vapor, then doping or functionalization strategies are used. A sensor array is constructed with 32-96 sensor elements with chemical variations across the sensor array. In the sensor training mode, a pattern of resistance changes is generated from the sensor array for a particular analyte at a given concentration and humidity level; this needs to be repeated for various concentrations and humidities and the generated information is stored for later use. In the identification mode, a pattern recognition algorithm is used to identify that analyte from the background using the information stored during training. This talk will present examples from our work to demonstrate the functioning of the sensor in security and biomedical applications. This sensor has also been integrated in an iPhone. We have recently made these sensors on cellulose paper substrates as well. In the case of the biosensor, a " lock and key " approach is used wherein a preselected probe for a given target is attached to the tip of a carbon nanofiber (CNF). CNFs in a patterned array are grown using PECVD on a silicon wafer which serve as individual, freestanding, vertical electrodes. This nanoelectrode array (NEA) can use DNA, aptamer and antibody probes, and electrochemical impedance spectroscopy is used upon probe-target binding for signal analysis. Results will be presented for identification of e-coli and ricin using this NEA and applications for security and biomedical sectors will be illustrated. For radiation sensing, we have developed a nanogap FINFET-like device wherein the nanogap can be filled with a radiation-responsive gel or liquid and demonstrated detection of gamma radiation. An array of devices with different liquids can be used in a multiplexed mode as a radiation nose.The author thanks Jing Li, Yijiang Lu, Jessica Koehne and Jinwoo Han.