Robotic Prototyping of Paper-Based Field-Effect Transistors with Rolled-Up Semiconductor Microtubes

In this article, we propose a robotic rapid prototyping technology for fabricating a new type of paper-based field-effect transistors (FETs). Unlike the existing paper-based electronics developed primarily based on the printing of conductive and semiconductive inks on paper substrates, this new prototyping technology integrates single rolled-up semiconductive microtubes into a device with robotically printed electrodes as the semiconductive channel, through robotic micromanipulation techniques. To improve the uniformity of the printed silver (Ag) ink electrodes, we designed a time-shift mechanism to compensate for the nonuniform ink dispersion at the beginning and ending phases of the robotic printing process. In addition, image processing and motion control algorithms were developed to enable automatic transfer of the prefabricated microtube from its hosting silicon wafer to the printed electrodes on a paper substrate. The effectiveness of the proposed technology was verified by fabricating the paper-based FETs with semiconductive zinc oxide (ZnO) microtubes. Preliminary tests on the mobility of the fabricated ZnO FET demonstrated improved performance over the conventional paper-based FETs with printed semiconductive channels.