The combination of biological molecules and CNTs is of great importance in developing miniaturized sensor devices for future clinical diagnostic and electronics applications. Biosensing technology using aligned CNTs solely depends upon amplified signals generated by biomolecular interactions. Aligned CNTs have huge potential as electrochemical sensors as they provide enhanced electron transfer in redox reactions due to high length to diameter (aspect ratio). CNT based functional devices including transistors, sensor, emitters and energy units require vertically aligned CNTs with a high length to diameter aspect ratio and their ability to mediate electron transfer reactions of electroactive species in solution when used as electrode material. Carbon nanotubes have been proved as better electrode materials than traditional carbon electrodes, clay nanoparticles and conducting polymers etc. due to their proficient charge transfer capability and high chemical stability. Major Aim of this book is to present clear idea to the readers who intend to devise a highly sensitive and efficient vertically aligned CNT based electrochemical sensors.