Needle-type field-effect transistor based on carbon nanotube derivative without lithography process

A carbon nanotube network field effect transistor was fabricated on the edge of a glass needle using no lithography. A glass pipette with solder inside was heated and stretched to form a needle. After Au layer deposition on the outer needle, a CNT network was fabricated by immersing the needle top into a CNT solution. The current between the solder and the Au layer, which depends on the liquid gate potential and the buffer pH, is measured. Because the needle configuration is controllable by heating the glass tube, it can be fabricated easily without lithography, producing sensors for use in various fields.