Highly Sensitive and Full Range Detectable Humidity Sensor using PEDOT:PSS, Methyl Red and Graphene Oxide Materials

Gul Hassan,Changhwan Choi,Memoon Sajid

doi:10.1038/s41598-019-51712-w

Gul Hassan, Changhwan Choi + Show 1 more

Open Access

https://doi.org/10.1038/s41598-019-51712-w

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Abstract

Single transducer with humidity sensing materials has limitations in both range and sensitivity, which cannot be used to detect the full range of humidity with consistent sensitivity. To enlarge range and improve sensitivity in the all range relative humidity (RH), we propose a highly sensitive and full range detectable humidity sensor based on multiple inter-digital transducer (IDT) electrodes connected in series with poly(3,4-ethylenedioxythiophene) doped poly (styrene sulfonate) anions (PEDOT: PSS), C15H15N3O2 (Methyl Red), and graphene oxide (GO) thin films as the active sensing materials. The humidity sensor with single active material has a limit in the detecting ranges, where the GO, PEDOT: PSS, and Methyl Red materials have sensing responses of 0 to 78% RH, 30 to 75% RH, and 25 to 100% RH, respectively. However, a humidity sensor using combined three active materials can respond to much wider range of RH with high sensitivity, where the IDTs and the active regions were prepared using ink-jet printing and spin coating, respectively. This proposed sensor can detect a full range of 0% RH to 100% RH. The response and recovery times are 1 sec and 3.5 sec, respectively. Our single sensing device using multiple IDTs connected different active materials in series can overcome the limitations of single transducer based sensor for the high performance sensor applications.

Highlights

Different kinds of materials have been studied for humidity sensing using ceramics[18], polymers[19], organic and inorganic semiconductors[20], composites[21,22] and oxides[23]
Surface morphologies of the active regions consisting of PEDOT: PSS, methyl red and graphene oxide (GO) thin film analyzed using FE-SEM are presented in Fig. 3, indicating that the sensing films are uniformly deposited
These results suggest that the PEDOT: PSS based active region has low sensitivity towards low humidity levels and higher sensitivity towards high level of surrounding environment humidity

Summary

Introduction

Different kinds of materials have been studied for humidity sensing using ceramics[18], polymers[19], organic and inorganic semiconductors[20], composites[21,22] and oxides[23]. Some humidity sensors were previously demonstrated with some advantages such as low cost, easiness to use, and low operational temperature with long lifetime, low sensitivity and limited detection range are still main concerns. To overcome these challenges, researchers are in the development using different materials and fabrication technologies[3], but still further investigations are needed. Sensor with methyl red-based active region showed linear sensing response towards higher humidity levels from 25% RH to 100% RH. The response and recovery times were excellent with values of 1 sec and 3.5 sec, respectively

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Results

Conclusion