Optical Fiber Sensors for Various Applications
Due to light weight/small size, high sensitivity/large band width, long range operation, and harsh environment capability, optical fiber has gained immense attention in sensor field. The optical fiber sensor can be either intrinsic or extrinsic type considering the passage of light and optical modulation mechanism can be by intensity, phase, wavelength and polarization. It has been used to measure various chemical and physical properties, such as temperature, pH, pressure, humidity, flow rate, gas concentration, liquid level, radiation, displacement, vibration, and chemical species.
My group has developed optical fiber sensors for 5 applications: (1) Aerosol (2) VOCs (3) Biomolecule, (4) Radiation and (5) Force.
(1) To detect aerosol, TEOS and thymol blue (TB) were used for the preparation of silica cladding on optical fiber core. The coated optical fiber is found to be sensitive to composition of aerosol based on evanescent wave absorption. Moreover, conductive polymer, polypyrrole (PPy) thin film coated optical fiber was used for NaCl, PSL, and BC aerosol sensing. (2) PPy thin film coated optical fiber was used for VOCs sensor. Its detection limit is ~1 ppm level. Similarly, DNA and metal ion-modified DNA (M-DNA) coated on quart plate was used for VOCs sensor based on surface change. M-DNA is more sensitive than DNA for sensing. Additionally, Graphene oxide (GO) and reduced-GO (rGO) were coated on tip of optical fiber and used for detecting 8 kinds of VOCs. (3) Reusable PDMS waveguide-graphene FET hybrid sensor was developed for bio-molecular interaction monitoring. Its sensing mechanism is based on changing evanescent field. Moreover, graphene was used as a novel surface plasmon supporting material for highly sensitive biosensors. Graphene was also employed as composite material with MoS2 for synergetic effect. The MoS2-graphene composite was used for electrochemical sensor with increasing sensitivity of PTH hormone. (4) Alpha radiation can induce tracks on the surface of CR 39/ LR 115 film. These tracks can be detected by the change of reflection light intensity. Blue light (450 nm) was used for real-time measurement of radiation damage of the surface and compared with AFM measurement. Similarly, DNA this film was utilized to observe the damage of its surface by 241Am (Alpha radiation source) for radiation sensor. (5) Finally, FBG (Fiber Bragg Grating) was used for force sensor with flexure structure and its wavelength change was used for changing force and it can be applied to catheterization.
In this lecture, I will review previous results from my group and discuss about the future direction.