Carbon nanotube (CNT) based devices include an actuator/switch that includes one or more fixed CNTs and a moveable CNT that can be urged toward or into contact with a selected fixed CNT with a magnetic field produced by a current in a control conductor. The control conductor can be formed of one or more CNTs, and the fixed and moveable CNTs can be retained by a support, and motion of the moveable CNT limited by a cavity defined in the support. In other examples, CNT FETS are used to form CNT transmission gates that are arranged to define circuits configured as multiplexers or to realize logical functions, addition, multiplication, or other operations such as Galois field arithmetic.