Related Experiment Video
Updated: May 24, 2025
07:28
Terahertz Microfluidic Sensing Using a Parallel-plate Waveguide Sensor
Published on: August 30, 2012
10.7K
pH Measurements Using Leaky Waveguides with Synthetic Hydrogel Films.
Victoria Wensley1, Nicholas J Goddard2, Ruchi Gupta1
1School of Chemistry, University of Birmingham, Birmingham B15 2TT, UK.
Micromachines
|March 6, 2025
Summary
This study introduces a novel leaky waveguide (LW) pH sensor using a pH-responsive hydrogel. This sensor offers fast, reversible pH measurements with high resolution, suitable for drinking water monitoring.
Area of Science:
- Materials Science
- Chemical Sensors
- Optoelectronics
Background:
- Leaky waveguides (LWs) are optical devices where light propagates within a thin film and leaks at the film-substrate interface.
- The optical properties of LWs, such as the angle of light propagation, are sensitive to the refractive index and thickness of the film.
- pH-responsive hydrogels can alter their properties based on surrounding pH, offering potential for sensor applications.
Purpose of the Study:
- To develop and characterize a leaky waveguide (LW) based pH sensor.
- To utilize a synthetic hydrogel with pH-responsive monomers for accurate pH measurements.
- To evaluate the sensor's performance, including response time, reversibility, selectivity, and resolution.
Main Methods:
- Fabrication of a leaky waveguide (LW) sensor using a hydrogel film composed of acrylamide, N-[3-(dimethylamino)propyl]methacrylamide (DMA), and a bisacrylamide crosslinker.
- Measurement of pH using the LW sensor in the range of 4 to 8.
- Assessment of sensor response time, reversibility, and selectivity against common interferents (NaCl, urea, Al2(SO4)3, CaCl2, humic acid).
- Comparison of the hydrogel LW sensor's performance with a conventional glass pH electrode.
Main Results:
- The hydrogel LW sensor demonstrated reversible pH measurements within the 4 to 8 range.
- Fast response times were observed: 0.90 ± 0.14 min for low-to-high pH changes and 2.38 ± 0.22 min for high-to-low pH changes.
- The sensor exhibited high selectivity, being largely insensitive to common interferents at typical concentrations.
- The hydrogel sensor achieved a pH resolution of approximately 0.004, surpassing the glass electrode's resolution of ~0.01.
Conclusions:
- The developed leaky waveguide (LW) hydrogel sensor is a promising technology for pH monitoring.
- Its fast response, high resolution, and selectivity make it suitable for applications like drinking water quality assessment.
- The sensor offers a viable alternative to traditional pH electrodes, particularly within its operational pH range.
