In addition, the dyes are superior to many other existing odor sensors in detecting toxic vapors, such as ammonia, and flammable vapors such as alcohols, benzene, and acetone. In a home, the technique could be adapted to determine food spoilage, aid in cooking, or detect harmful vapors. The ink can be considered intelligent for two reasons. First of all, as the ink dries after printing, its particles assemble themselves into orderly layers with spaces, forming a complex structure of nanoscopic pores, each leading to the next. Secondly, ligands can be sprinkled into the ink.
Ligands are active molecules that exhibit molecular recognition characteristics.
These ligands, taking up residence in the nanoscopic pores, could be used to interrogate anything passing through, such as a gas or fluid, laser light, or an electric or magnetic field. As a result, the ink pattern can behave as an array of sensors. Prototypes of the concept have already been used to monitor the pH of fluids transported by capillary action, with color-changing ligands used to indicate pH level. By linking a CAD system with an ink-jet printer using intelligent ink, it will be possible to create, in seconds, a functional, hierarchical nanostructure that was a mere drawing on a computer screen moments before. Essentially, this will allow those with the technical ability to directly write, rather than mechanically construct, sensor arrays or fluidic or photonic systems, says project leader Jeff Brinker.