Fabrication of carbon nanotube-based pH sensor for paper-based microfluidics

A fabrication method for carbon nanotube (CNT)-based sensors on paper is proposed and provides a repeatable and well-controlled method for constructing a functional paper-based analytical device. The proposed method is based on vacuum filtration process with a metal mask covering on a filter paper for the definition of the sensor dimension. The length, width, and thickness of the CNT-based sensors are readily controlled by the metal mask and the weight of the CNT powder used during the filtration process, respectively. Homogeneous deposition of CNTs with well-defined dimensions on paper can be achieved. The CNT-based sensors showed linear I-V response and their resistances can be designed from 0.3 to 4.6 k Omega based on their dimensions. Moreover, the CNT-based sensor on paper has been demonstrated on the detection of the pH value of the analyte solution. It showed the CNT is sensitive to the chemical molecules and the CNT-based sensor is a possible candidate for chemical and biosensors. Thus, electrical bio-assays on paper-based microfluidics can be realized to develop low cost, sensitive, and specific diagnostic devices. (c) 2012 Elsevier B.V. All rights reserved.