Abstract
We present a flow-through refractive index sensor for measuring the concentration of glucose solutions based on the application of rectangular glass micro-capillaries, with channel depth of 50 µm and 30 µm. A custom designed and 3D printed polymeric shell protects the tiny capillaries, ensuring an easier handling and interconnection with the macro-fluidic path. By illuminating the capillary with broadband radiation centered at λ~1.55 µm, both the transmitted (T) and reflected (R) optical spectrum from the capillary are detected with an optical spectrum analyzer, exploiting an all-fiber setup. Monitoring the spectral shift of the ratio T/R in response to increasing concentration of glucose solutions in water we have obtained sensitivities up to 530.9 nm/RIU and limit of detection in the range of 10-5-10-4 RIU. Experimental results are in agreement with the theoretically predicted principle of operation. After the demonstration of amplitude detection at a single wavelength, we finally discuss the impact of the capillary parameters on the sensitivity.
Highlights
In the last few years, increasing attention has been paid to optical sensors for the detection of fluid refractive index (RI) and/or of solution concentration
By monitoring the wavelength shift of the T/R peaks induced by solutions of glucose in water at different concentrations, we have demonstrated sensitivities in the range from 258.0 nm/RIU up to 530.9 nm/RIU and limit of detection (LOD) in the range of 10−5-10−4 RIU
Readout radiation in the near-infrared range was provided by a Superluminescent Light Emitting Diode (SLED) source with peak emission wavelength λc ~1549 nm, Full Width at Half Maximum (FWHM) bandwidth of 57 nm and optical power coupled in standard single-mode optical fibers of approximately 1.8 mW when driven by a pumping current of I = 180 mA at a temperature of 20 °C
Summary
In the last few years, increasing attention has been paid to optical sensors for the detection of fluid refractive index (RI) and/or of solution concentration. Optical read-out is undoubtedly a very fascinating solution among detection methods, as it allows remote sensing of the investigated parameters, being minimally invasive, while miniaturization enables testing with ultra-low quantities of materials, both important factors in the fields of biological, biochemical and biomedical analyses [2]. Rectangular cross-section capillaries, in particular, are better suited for optical read-out methods, thanks to their flat surface that reduces scattering and optical distortions usually occurring with circular capillaries [20]. They resemble an optical resonator, composed by three flat parallel slabs, i.e., two glass walls and the internal channel [22,23]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
