A New Strategy to Prepare Carbon Nanotube Thin film by the Combination of Top-down and Bottom-up Approaches

Bottom-up and top-down are two different strategies to prepare nano-materials and their assemblies, each with their own pro-and-cons. Here, we demonstrate a combined approach in preparing large area uniform carbon nanotube (CNT) thin films within minutes, several orders of magnitude faster than conventional methods. This strategy takes full advantage of the unique micro-structure of CNT sponges, synthesized by a bottom-up process and composed of physically entangled CNTs with uniform size and spatial distribution. Such a 3D network structure allows us to firstly transfer certain amount of structured CNTs from the sponge onto a Scotch tape. Through a second-step stamping process, which is essentially a top-down process, transparent and conductive (TCF) CNT films with controlled micro-structures are produced on viscous substrates. Bonding strength between the stamped CNT network and elastomer substrate can be adjusted to optimize the physical properties including the transparency and sheet resistance of the CNT thin films. Upon stretching, the device exhibits high piezoresistive responsiveness; combining high sensitivity, low hysteresis and large working strain range. The proposed methodology had been extended to fabricate micro-electrodes on patterned elastomers with same effectiveness. These experimental results highlight the high efficiency, low-cost and versatility of this approach in preparing TCF electrodes with different sizes and shapes.