3. Carbon Nanotube Structures with Sensing and Actuating Capabilities

We describe carbon nanotube (CNT) structures which are used as mechanical sensors, electromechanical actuators and shape memory materials. These structures include CNT mats and fibres of aligned CNTs. Mechanical sensors are based on the piezo-resistivity of the investigated CNT structures. They can be used as embedded sensors for sensing and damage monitoring of composites. CNT can also be used for novel actuator technologies. Indeed CNTs deform in response to charge injection and electrostatic phenomena. They can be stimulated under the form of electrodes in a given electrolyte. CNT structures can generate a large stress because of their stiffness. In other classes of actuating materials, carbon nanotubes can be used as fillers of shape memory polymers (SMPs). SMPs have applications in packaging, biomedical devices, heat shrink tubing, deployable structures, etc. CNTs are ideal materials to improve the stiffness of shape memory polymers, which is critical for achieving large stress recovery. Their electrical conductivity is of particular interest in the engineering of SMPs which can be heated via Joule’s heating and directly stimulated by an electrical current. We review in this chapter the properties of these new functional materials and highlight their potential for future applications.