Polymer Microtip-Based Fabry-Perot Interferometer for Water Content Determination in the Gas and Liquid Phase.

Area of Science:

• Optical sensing
• Polymer science
• Analytical chemistry

Background:

• Accurate water content determination is crucial across various industries.
• Existing methods may lack sensitivity, directness, or applicability to both gas and liquid phases.
• Development of novel sensing platforms is needed for improved water analysis.

Purpose of the Study:

• To develop and characterize a Fabry-Perot interferometer (FPI) sensor based on a polymer microtip for water content determination.
• To evaluate the sensor's performance in both gas and liquid phases.
• To assess the sensor's sensitivity, selectivity, and stability.

Main Methods:

• Fabrication of a pentaerythritol triacrylate (PETA) polymer microtip at the end of an optical fiber using self-guiding photopolymerization.
• Utilizing the microtip as a low-fineness FPI and a sensing layer due to its hydroxyl groups.
• Experimental characterization of the FPI signal response to varying water content in gas (relative humidity) and liquid (water/glycerol mixtures).
• Investigation of temperature cross-sensitivity.

Main Results:

• The PETA-based FPI sensor demonstrated a clear interferometric signal highly sensitive to water content.
• In the gas phase, a constant sensitivity of 90 pm/%RH (104 ppm/%RH) was observed for relative humidity from 30-80%.
• In the liquid phase, a nonlinear sensitivity up to 158 pm/wt % was achieved for water content below 40 wt %.
• The sensor exhibited negligible cross-sensitivity to temperature variations (23-70 °C).

Conclusions:

• The polymer microtip FPI sensor enables direct, sensitive, and reliable water content determination in both gas and liquid phases.
• The sensor's performance is robust, with high sensitivity and minimal temperature interference.
• This technology holds significant promise for advanced water analysis in diverse product applications.