Method and apparatus for controlling the length of a carbon nanotube

A method for controlling the length of a carbon nanotube, comprising the following steps:

• providing a substrate having a first surface on which an array of microstructures is disposed wherein at least one carbon nanotube is formed on at least one microstructure, and at least a second surface forming a reference level, wherein the shortest vertical distance of the top of said at least one carbon nanotube above said reference level is H;
• providing at least one positioning platform capable of carrying and moving said substrate;
• mounting said substrate onto said positioning platform;
• providing a discharging electrode and a piezoelectric actuator which positions said discharging electrode;
• providing a position sensor for detection of the height of said discharging electrode relative to said reference level to calibrate the position of said substrate or said discharging electrode in accordance with the height sensed with said position sensor, wherein the vertical distance of said discharging electrode above said reference level is I;
• and
• moving said substrate with said positioning platform and simultaneously applying a voltage pulse to said discharging electrode, wherein H is not less than I such that said discharging electrode cuts the at least one carbon nanotube.