Abstract
In this study, analysis of sensing signal profiles was conducted focusing on the close relationship between electrical conductivity and signal intensity in surface treated poly(dimethylsiloxane)/carbon nanotube (PDMS/CNT) composite patches for the purpose of their practical application as flexible chemical sensors. The flexible PDMS/CNT composite patches were prepared from a PDMS/CNT mixture with a two-roll apparatus. It was found that the PDMS/CNT pads showed a high electrical conductivity (10−1 S/m) even at low CNT loading (0.6 wt %) and a contact angle range of 105–118°. The surface of the obtained PDMS/CNT composite patches was treated using a simple bio-conjugation method to incorporate beta-cyclodextrin (beta-CD) molecules onto the surface as a sensing medium, in order to detect a model compound (Methyl Paraben, MePRB). FT-IR spectra indicated that beta-cyclodextrin molecules were effectively introduced on the surface of the PDMS/CNT patches. It was shown that the sensor signal intensity was substantially dependent on the base current value, which increased with increasing CNT loading. Accordingly, the base current value was intimately associated with the electrical conductivity of the composite patches. On the other hand, the increase in current over the base current (ΔI/I0) obtained after the addition of the model compound was inversely proportional to the CNT content. In this way, analysis on the sensing signal profiles of the flexible chemical sensor system was conducted to determine a process window. This study is a very useful springboard for future research activities, as more profound studies are necessary to fully understand sensing signal profiles.
Highlights
The need for ultrasensitive and flexible chemical sensors has been increasing in recent times, as it is becoming important to detect ultrasmall amounts of toxic gases/chemicals, hazardous materials, pathogens, and microorganisms for human safety [1,2,3,4,5]
Introduction of the PDMS/CNT composites for ultrasensitive chemical sensors is still challenging, because the responses of the PDMS/CNT composites to stimuli are not adequately rapid and selective
The first important step of this study was the preparation of flexible PDMS/CNT composite
Summary
The need for ultrasensitive and flexible chemical sensors has been increasing in recent times, as it is becoming important to detect ultrasmall amounts of toxic gases/chemicals, hazardous materials, pathogens, and microorganisms for human safety [1,2,3,4,5] To this end, it is critical to obtain electrically conductive and flexible substrates, because the use of electrical signals is considered as one of the most efficient signal transduction mechanisms in sensing and flexible substrates can be applied onto. As an example of developing flexible chemical sensors using PDMS/CNT composites, in the previous study, the sensing of a toxic chemical based on a surface engineered PDMS/CNT composite patch was systematically investigated. While the characterization and analysis methods are straightforward, this study is a sound experimental demonstration of the fundamental aspects of a flexible chemical sensor using an electrically conductive substrate, which may be useful for future applications
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