Revolutionizing pH Measurement with Contactless Radiofrequency Sensing

Accurate pH measurement is essential across a broad range of industries, from environmental monitoring and industrial processing to biomedical applications. Traditional methods, such as electrode-based and optical sensors, require direct contact with the liquid analyte, which can introduce contamination risks, sensor degradation, and operational constraints. But what if we could measure pH levels without ever touching the liquid?

A recent study, conducted by researchers from Central Washington University, introduces a novel approach to pH measurement using radiofrequency (RF) sensing—completely contact-free. This groundbreaking research, available as a preprint here, demonstrates how RF-based detection can offer a non-invasive alternative to traditional pH measurement methods.

How Does Contactless pH Measurement Work?

The study utilized Know Labs’ patented RF dielectric sensor, which measures changes in frequency response when placed near a liquid sample. The sensor was positioned against the outside of a PVC pipe containing a liquid solution, and a frequency sweep from 300 MHz to 4100 MHz was conducted to capture RF signal variations. By applying inverse discrete Fourier transform (IDFT) analysis, researchers identified sinusoidal patterns in the frequency response data that correspond to changes in pH.

Unlike previous RF-based pH measurement methods that relied on chemical exchange saturation transfer (CEST) MRI or single-frequency microstrip antennas, this new approach leverages a wide spectrum analysis combined with machine learning techniques to enhance accuracy and reliability.

Key Findings

1. High Sensitivity and Accuracy

   • The system was able to detect even minor pH changes by analyzing how RF signals interacted with hydronium ion concentrations in solution.

2. Non-Invasive and Versatile

   • The RF sensor does not require direct contact with the liquid, reducing contamination risks and eliminating the need for disposable electrode probes.

   • This method can be applied to solutions contained in plastic, making it particularly useful for industrial and biomedical applications where traditional probes may be impractical.

3. Potential for Broader Applications

   • The ability to detect pH changes without contact opens doors for real-time monitoring in pharmaceuticals, food production, and medical diagnostics.

   • Future studies will explore whether this method can be used to distinguish between different acid types and evaluate its effectiveness in complex solutions.

What’s Next?

This study marks a major step forward in RF-based chemical sensing. While initial results are promising, future research will aim to refine the technique by expanding the range of pH values tested, investigating its application in real-world scenarios, and enhancing machine learning models for even greater predictive accuracy. The potential of RF technology in non-invasive diagnostics continues to grow, and this study highlights yet another innovative application.

To learn more, read the full study here. Stay tuned for more breakthroughs from Know Labs as we push the boundaries of contactless sensing technology!