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Researchers from Universidad Politécnica de Madrid (UPM) have developed an innovative optical sensor using conventional tape, a low-cost and flexible material that can be easily acquired at stationery shops. It can detect variations of the optical properties of a liquid when is immersed. The sensor can be used to control both the quality of beverages and environmental monitoring.
Light from an LED is introduced in one of end of a piece of tape and the light that emerges from the other end is detected through a photodiode. The light coupling to the flexible waveguide is mediated by a diffractive element using a grating with aluminum lines of nano dimensions; it is added to the tape through a simple process of "tear and paste." Both ends of the waveguide can be easily adhered to the LED emitter and the light detector (photodiode).
Flexibility - Tape - Waveguide - Liquid - Examination
Because of the flexibility of the tape, the waveguide can bend and is partially immersed in the liquid under examination. Due to the waveguide bend, part of the propagated light is lost by radiation. This curvature loss depends on the refractive index of the surrounding medium. Thus, it is possible to detect variations of the refractive index of the liquid by photodiode measurement of the optical power lost during the path of light through the immersed...
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