A thin-film transistor based acetylcholine sensor using self-assembled carbon nanotubes and SiO2 nanoparticles

A high sensitivity acetylcholine (ACh) sensor is developed using a nanomaterial-based thin-film transistor. The device fabrication combines the “bottom-up” layer-by-layer self-assembly and the “top-down” microfabrication techniques. The transistor uses a self-assembled single-walled carbon nanotube (SWNT) multilayer as the semiconducting film. Silicon dioxide (SiO2) nanoparticles are deposited on the substrate as the dielectric material. Acetylcholinesterase (AChE) enzyme molecules are immobilized on the surface as the sensing film, which can induce the ACh hydrolysis reaction and release hydrogen ions to the solution. Because all the assembly steps of the multilayer films are done in solutions at room temperature, the fabrication complexity and the process cost are dramatically reduced. The transistor-based sensor demonstrates high sensitivity for ACh sensing and shows a good linearity in the high ACh concentration range. The sensitivity, resolution, and response time of the sensor are measured as 378.2 μA/decade, 10 nM, and 15 s, respectively. This work presents a promising technique to develop disposable and high-sensitivity biosensors for a wide range of applications.