Surface Area Enhancement of Nanomechanical Disk Resonators Using MWCNT for Mass-Sensing Applications

This work presents fabrication of thermal-piezoresistive nanoelectromechanical silicon disk resonators and their characterization as highly sensitive mass sensors. Forest of multiwall carbon nanotubes (MWCNTs) has been grown on the top surface of the fabricated devices, increasing the resonator effective surface area, which, in turn, increases the adsorption capacity and, therefore, the frequency shift of the sensor in molecular or particulate detection applications. To investigate the effect of the enhanced surface area on frequency shift, devices with and without MWCNTs were exposed to an aqueous solution of manganese sulfate for different deposition times and the resonance frequency shift was recorded accordingly. The measured frequency shift for the devices covered with MWCNTs was 14× higher than similar bare silicon devices. Furthermore, mass loading experiments were performed using gold nanoparticles as the loading mass. A novel way to attach gold nanoparticles on the carbon nanotubes (CNTs) wall was developed here. Oxygen plasma treatment introduced dangling bonds on the MWCNTs walls to facilitate the bonding between them and trimethoxysilane aldehyde molecules, forming the selfassembled monolayer (SAM). After functionalization of the device with SAM and antiinfluenza H1N1 viruses (AB), the device was exposed to a solution of Antimouse IgG (whole molecule)-gold antibody produced in goat products. The results showed more than three times response enhancement for the resonators with MWCNTs.