Fabrication of freestanding micro hollow tubes by template-free localized electrochemical deposition

Abstract

The present invention relates to a method of fabricating a micro hollow tube. More specifically, the invention relates to a method of fabricating a micro hollow tube by template-free localized electrochemical deposition, in which the micro hollow tube is fabricated by the accurate control of the distribution of the electric field strength during deposition with precise interplay of the applied voltage and the distance between the microelectrode and the grown structure.

1 . A method of fabricating a micro hollow tube by template-free localized electrochemical deposition, the method comprising the steps of: ( a ) placing a microelectrode (anode) very close to a substrate (cathode) immersed in a plating bath; and ( b ) applying a voltage greater than a critical voltage to the microelectrode and the substrate via a electrochemical medium, and thereby to form a micro hollow tube structure on the substrate, 
       wherein the critical voltage is defined as the applied voltage when a maximum electric field position moves from the center of the end of the micro hollow tube structure into the edge of the end of the micro hollow tube structure just below the rim of the tip of the microelectrode. 
     
     
         2 . The method of fabricating a micro hollow tube according to  claim 1  further comprises ( c ) moving up the microelectrode from the formed micro hollow tube structure, with a contact growth mode being kept during deposition. 
     
     
         3 . The method of fabricating a micro hollow tube according to  claims 1  and  2 , wherein a position of the microelectrode relative to the substrate or the micro hollow tube structure is directly observed by using an image collecting apparatus. 
     
     
         4 . The method of fabricating a micro hollow tube according to  claim 3 , wherein the image collecting apparatus is a microradiographic apparatus with coherent X-rays in real time. 
     
     
         5 . The method of fabricating a micro hollow tube according to  claim 4 , wherein the microradiographic apparatus comprises a X-ray beam source, a sample stage, and an image detecting means. 
     
     
         6 . The method of fabricating a micro hollow tube according to  claim 2 , wherein the movement of the microelectrode is performed with three stepping motors in sub-microns. 
     
     
         7 . The method of fabricating a micro hollow tube according to  claim 1 , wherein the micro hollow tube comprises at least one selected from the group consisting of a metal and a metal alloy.