Biocompatible fiber-optic pH sensor based on optical fiber modal interferometer self-assembled with sodium alginate/polyethylenimine coating

Bobo Gu, Mingjie Yin, Aping Zhang, Jinwen Qian, Sailing He

Research output: Journal article publicationJournal articleAcademic researchpeer-review

30 Citations (Scopus)


We report a new biocompatible fiber-optic pH sensor based on optical fiber modal interferometer. Two biocompatible polyelectrolytes, i.e., sodium alginate (SA) and polyethylenimine (PEI), are alternatively deposited on the side surface of the thin-core fiber modal interferometer (TCFMI) via a layer-by-layer (LbL) electrostatic self-assembly (ESA) technique for pH sensing applications. With a measurement of water contact angles, it is revealed that the hydrophilicity of such a coating depends on the pH values. The refractive index (RI) of the coating is modulated through swelling/deswelling behavior when the pH of the solution is changed. The induced RI change is precisely determined by the TCFMI through a measurement of the destructive-interference wavelength. The thickness and morphology of the self-assembled sensing coating are characterized by using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The sensor exhibits a liner, fast, reversible and monotonic response in a large pH range with resolution of 0.0093 pH unit which makes the sensor very promising for biomedical and clinical pH measurement applications.
Original languageEnglish
Article number6060851
Pages (from-to)1477-1482
Number of pages6
JournalIEEE Sensors Journal
Issue number5
Publication statusPublished - 24 Apr 2012
Externally publishedYes


  • Electrostatic self-assembly
  • optical fiber interferometer
  • optical fiber sensor
  • pH biosensor

ASJC Scopus subject areas

  • Instrumentation
  • Electrical and Electronic Engineering

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