When it comes to detecting and discriminating between a diverse variety and large number of substances, biological noses are unparalleled. UPenn researchers hope to change that in the near future, and have demonstrated the use of carbon nanotubes that can get close. By attaching specially-made DNA strands to carbon nanotubes, the team has constructed highly sensitive chemical sensors with unparalleled ability to distinguish different types of molecules. The DNA molecules, affixed to carbon atoms that make up nanotubes, bind to particular molecules present in the air and change the electrical conductivity of the nanotubes. The researchers can detect these electrical signals and detect very low concentrations of various chemicals. Their eventual goal is to combine a wide variety of specialized chemical sensors to create an actual electronic nose.