Nanotextured Surface on Flexographic Printed ZnO Thin Films for Low-Cost Non-Faradaic Biosensors

In this work, the formation of a nanotextured surface is reported on flexographic printed zinc oxide thin films which provide an excellent platform for low-cost, highly sensitive biosensing applications. The ability to produce nanotextured surfaces using a high-throughput, roll-to-roll production method directly from precursor ink without any complicated processes is commercially attractive for biosensors that are suitable for large-scale screening of diseases at low cost. The zinc oxide thin film was formed by printing a zinc acetate precursor ink solution and annealing at 300 °C. An intricate nanotexturing of the film surface was achieved through 150 °C drying process between multiple prints. These surface nanostructures were found to be in the range of 100 to 700 nm in length with a width of 58 ± 18 nm and a height of between 20 and 60 nm. Such structures significantly increase the surface area to volume ratio of the biosensing material, which is essential to high sensitivity detection of diseases. Nonfaradaic electrochemical impedance spectroscopy measurements were carried out to detect the pp65-antigen of the human cytomegalovirus using the printed device, which has a low limit of detection of 5 pg/mL.