ZnO Nanorods Coated Tapered U-Shape Plastic Optical Fiber for Relative Humidity Detection

Siti Halma Johari, Tiu Zian Cheak, Hazli Rafis Abdul Rahim, Mohd Hafiz Jali, Haziezol Helmi Mohd Yusof, Md Ashadi Md Johari, Moh Yasin, Sulaiman Wadi Harun

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


A relative humidity sensor was fabricated by exploiting an evanescent wave (EW) on a U-bent tapered plastic optical fiber (POF) coated with zinc oxide (ZnO) nanorods. The POF was tapered manually using a polishing method to a diameter of 0.5 mm, a length of 5 cm, and a radius of 5 cm. ZnO nanorods were synthesized using a hydrothermal method and grown on the POF by a seeding process for 12 h. A significant response of the sensor was observed when the sensor was exposed to 35 to 90%RH due to the intense chemisorption process and changeable relative index in the POF. The sensitivity and resolution of the sensor have been improved by factors of 1.23 and 2.18, respectively, compared to the conventional tapered POF sensor without ZnO coating. Besides, the ZnO-coated sensor also exhibited better repeatability properties in terms of output voltage when exposed to 35 to 90%RH for three repeated measurements. The obtained results revealed that the proposed new POF sensor has an excellent sensing performance as an RH sensor in terms of sensitivity, repeatability, and stability properties.

Original languageEnglish
Article number796
Issue number11
Publication statusPublished - Nov 2022


  • evanescence wave sensor
  • humidity sensing
  • tapered plastic optical fiber
  • zinc oxide nanorods


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