Nanolitre solution drop-casting for selective area graphene oxide coating on planar surfaces

Abstract

Selective area coating of graphene and graphene oxide thin films provides a cost-effective approach for the integration of functional materials in electronics and photonics devices, such as transparent conductive electrodes, humidity sensors and optical modulators. For solution dispersed graphene oxides, solution drop-casting technique is commonly used. To produce coatings with precise thickness and coating area control, the dispensing volume and solution concentration in turn needs to be precisely controlled. Herein, we report a nanolitre solution drop-casting technique for selective area graphene oxide (GO) thin film coatings. A motorized actuator was used to control the micro-syringe to dispense precise volume of GO solution down to the nanolitres level. GO coatings using the proposed method were performed on two surfaces with different surface characteristics: thermal oxide (TOx) layer and photoactive UV curable resin (ZPU13-RI polymer) layer. We found that the difference in surface characteristics of both substrate surfaces greatly affects the diameter and thickness of GO coatings produced. The minimum diameter of GO coating obtained on TOx surface was 52 ± 5 μm, while the minimum GO coating diameter obtained on ZPU13-RI surface was 340 ± 17 μm. By controlling both the solution volume and solution concentration, single- and few-layer GO coatings can be produced on both TOx and ZPU13-RI surfaces using this technique. When integrated with 2-axis automated movement system, this technique can be used for selective area coating of GO thin film with controlled thickness on large planar surfaces such as in the production of sensors and other functional devices.