Reporting their results in the journal Nanotechnology, researchers in China have developed a facile and controllable method for wafer-scale deposition of SWNT networks. The technique is especially attractive because of its simplicity. The process is inherently low cost and flexible because it operates at atmospheric pressure and room temperature.

SWNT networks are obtained by immersing a pre-treated substrate in an aqueous suspension of SWNTs. The density of the deposited SWNT networks can be easily controlled by changing the concentration of the SWNT suspension and the deposition time. The deposited SWNT layer is uniform at the wafer scale, which is good for practical sensing applications.

Device assembly and testing

To provide good electrical contacts, the group from Shanghai Jiao Tong University created interdigitated arrays of gold electrodes (a finger of 600 µm and a gap size of 10 µm) on top of its nanotube networks using microfabrication procedures. Changes in the resistance of the nanotube networks when exposed to DMMP vapour were monitored by applying a 300 mV voltage across the electrodes.

The low power consumption of the deposited SWNT sensors will ultimately lead to longer sensor battery lifetime and a greater potential for applications. The sensors exhibit a high resistance response, fast response time, rapid recovery and good reproducibility for DMMP vapour. Potentially, manufacture of the deposited SWNT sensors can be extended to large-scale fabrication.