A dual-parameter optical sensor fabricated by gradient axial doping of an optical fibre

Abstract

There is a general need for optical sensors that respond to multiple substances or physical parameters. Multiple-parameter sensing is not only more efficient, but also permits interacting or interdependent parameters to be individually determined. In this paper, we describe a novel approach to the fabrication of an optical sensor, sensitive to two separate atmospheric conditions, but made from a single fibre optic. The optical fibre is drawn from polycarbonate, with a temperature-sensitive phosphor (La2O2S:Eu3+) incorporated directly into the core. Thus, the light-guiding portion of the fibre is responsible for determining the first parameter of measurement, ambient temperature. A thin fibre cladding is subsequently added to the temperature-sensitive core and serves as a chemically sensitive component. This cladding is made from Nafion®, and is doped with rhodamine 800. Fluorescence at 750 nm from the rhodamine 800 is shown to be enhanced by the presence of atmospheric moisture, and is used in conjunction with a ratiometric means of measuring temperature provided by the phosphorescence from the fibre core. This scheme provides a simple and potentially inexpensive way to manufacture fibre-optic sensors capable of multicomponent determinations. In addition, the temperature-sensitive core material provides a built-in normalization factor for the temperature-dependent response of the chemically sensitive cladding. The developed dual sensor was evaluated over the temperature range from 20 to 95 °C and demonstrated better than 1% relative standard deviation (RSD). The humidity sensor component was evaluated over the range of relative humidity (RH) from 0 to 20% RH over temperatures up to 56 °C. The detection limits for the humidity sensor were 0.17 and 2.35% RH at 20 and 56 °C, respectively.

Combinatorial and High-Throughput Screening of Materials Libraries: Review of State of the Art

“…For CHT screening, sensing materials candidates are arranged as discrete and gradient materials arrays. A wide variety of array fabrication methods have been reported as summarized in Table . − A specific type of library layout depends on the required density of space to be explored, available library-fabrication capabilities, and capabilities of high-throughput characterization techniques. Upon array fabrication, the array is exposed to an environment of interest and steady-state or dynamic measurements are acquired to assess materials performance.…”

Multivariable Sensors for Ubiquitous Monitoring of Gases in the Era of Internet of Things and Industrial Internet

“…Material-based multivariable photonic sensors go back to ratiometric probes that provided light-intensity- or temperature-independent measurements. Follow-up developments included sensing materials formulated with several reporter moieties .…”

Analytical instrumentation infrastructure for combinatorial and high-throughput development of formulated discrete and gradient polymeric sensor materials arrays

“…Discrete sensor regions are straightforward to produce using existing liquid-dispensing robotic equipment. Gradient sensor materials can be produced using solventassisted polymerization, 14 fiber drawing, [34][35][36] or draw coating. Ink jet printing typically produces dispense volumes of around several picoliters while the liquid dispensing robots can dispense several nanoliters and up to several microliters.…”