Multi-Transducer Arrays using Nanoparticle Interface Layers for Vapor Discrimination

Lindsay K. Amos, Kee Scholten, and Edward T. Zellers

Transducers employed in this study (from left to right): chemiresistor (CR) array (5 mm electrode gaps) ; CR array (0.1 mm electrode gaps); thickness shear mode resonator (TSMR); and opto-fluidic ring resonator (OFRR).

This project explores the development of multi-transducer (MT) arrays as detectors for a microscale gas chromatograph (mGC). Single transducer (ST) arrays, consisting of a set of the same transducers coated with different sorptive interface layers, are the most common types of arrays developed to date. The collective response patterns derived from such arrays, however, have limited diversity and therefore cannot differentiate among the components of mixtures of more than two vapors. MT arrays should offer greater diversity by virtue of probing multiple aspects of the vapor-interface interactions. We are studying combinations of three transducer types: chemiresistors (CR), which respond to changes in the volume and dielectric constant of the interface film; thickness shear mode resonators (TSMR), which respond to changes in the mass of the interface; and opto-fluidic ring resonators (OFRR), which respond to changes in the refractive index of the interface. Interfaces consisting of thin films of thiolate-mon layer protected gold nanoparticles (MPN) with different thiolate functionalities are used to impart chemical selectivity. The extent to which using an MT array increases the diversity of responses relative to an ST array of similar dimension (number of sensors) is being explored, along with the implementation of optimized MT arrays as μGC detectors for analyses of multi-vapor mixtures. This work is being funded by the Department of Homeland Security, Science and Technology Directorate.