(93e) Developing Low-Cost Nano/Micro Wire Sensors Based on a Seed-Mediated Solution Process
Nanowire sensors are widely recognized as the next generation building block for chemical sensing. They offer high commercial potential in many fields including defense, environmental monitoring, food safety, and industrial operations. Existing sensors tend to underperform on one or more of the sensor performance metrics, despite ongoing incremental improvements in readout time, miniaturization, and cost. Our low-cost nano/micro wire sensors are fabricated on microchips containing photolithographic patterns from solution droplets by applying an electrical pulse. It is a room temperature and reversible process allowing for portable and reusable products. The sensor performance is further tunable by versatile organic chemistry. Our technology is also compatible with both silicon and plastic electronics. The organic crystalline materials used for the sensing component are tetrathiafulvalene bromide charge transfer salt (TTFBr) and potassium tetracyanolantinate (KCP). The sensor is made by electrochemical deposition of TTFBr or KCP, from a solution droplet, on gold photolithographic patterns on glass. The sensitivity, specificity, and recyclability data are measured by impedance spectroscopy in the presence of various gases. The sensors can detect ammonia, hydrochloric acid, and other toxic or flammable gases at concentrations as low as 2 ppm. The specificity of the sensor corresponds to the polarity of the vapors. It responds more sensitively to more polar molecules. The sensor can be recycled at least 10 times without significant reduction in its performance. The likely mechanism is the interaction between the gas molecule and the organic nanowire crystalline face that leads to changes in bulk electrical conductivity of the nanowire. The conductivity can be sensitively tuned by the chemical nature of the nanowire.