An Optical Reporting Patch for Spatiotemporal Measurements of Water Activity in Complex Environments.

Area of Science:

• Materials Science
• Environmental Science
• Analytical Chemistry

Background:

• Water activity (a_w) is a critical parameter in diverse natural and technological systems.
• Current methods for in situ water activity measurement lack sufficient spatial and temporal resolution.

Purpose of the Study:

• To develop a novel sensing material for accurate in situ water activity monitoring.
• To demonstrate the capabilities of the developed technology for various measurement scenarios.

Main Methods:

• Development of a composite silicone patch (AquaSheet) that transduces water activity into a fluorescence signal.
• Implementation of two measurement modes: spatially averaged (using reflectance probe and spectrometer) and spatiotemporally resolved (using a custom imaging system).

Main Results:

• AquaSheet successfully reports water activity as a fluorescence signal.
• Demonstrated effective in situ measurements in both gaseous and liquid phases.
• Successfully tracked the spatiotemporal evolution of soil drying processes.

Conclusions:

• AquaSheet offers a promising new tool for in situ water activity measurement with high spatial and temporal resolution.
• The technology has potential for broad applications, with opportunities for further development and improvement.