How carbon nanotube sensors works? Is the protein (or chemical compound used as part of the sensor) placed inside the tube or where is it placed? and how is the technology used to place the protein there?
In the National Geographic magazine we can read (speaking about a young inventor)
he could interweave antibodies sensitive to mesothelin into a network of carbon nanotubes. High levels of the protein in a drop of blood from someone with pancreatic cancer would attach to the antibodies and cause them to enlarge, thus changing the network's electrical charge and signaling the cancer's presence.
In the Smithsonian magazine we can read
What if he could lace a nanotube network with mesothelin-specific antibodies, then introduce a drop of a pancreatic cancer patient’s blood? The antibodies would bind to the mesothelin and enlarge. These beefed-up molecules would spread the nanotubes farther apart, changing the electrical properties of the network: The more mesothelin present, the more antibodies would bind and grow big, and the weaker the electrical signal would become.
The tubular nature of CNTs allows for internal protein encapsulation, and also for their external coating by protein cages, affording bottom-up ordering of molecules in hierarchical structures. To achieve such complex systems it is imperative to master the intermolecular forces between CNTs and proteins, including geometry effects (e.g. CNT diameter and curvature) and how they translate into changes in the local environment (e.g. water entropy).