# Novel Spiral and Embracing IDE Capacitive Sensors for In Situ Measurement of Soil Moisture

## TL;DR

A new capacitive sensor design for measuring soil moisture shows high accuracy and stability, outperforming traditional sensors.

## Contribution

The novel spiral and embracing IDE sensor configurations offer improved sensitivity and electric field penetration for soil moisture measurement.

## Key findings

- The spiral IDE sensor achieved an R2 of 0.9976 and MSE of 0.859, showing strong stability and repeatability.
- The sensor outperformed commercial sensors with an R2 of 0.9995, closely matching gravimetric measurements.
- The design is promising for in situ soil moisture monitoring and landslide prevention.

## Abstract

A novel capacitive interdigital electrode (IDE) sensor for the in-situ measurement of soil moisture is presented. Two planar electrode configurations, spiral and embracing, were designed and evaluated through modeling, simulation, fabrication, and experimental validation. Compared with conventional circular and square electrodes, the proposed structures exhibited higher sensitivity and greater electric field penetration, with the spiral configuration offering the advantage of easier fabrication. The experimental results demonstrated that the calibrated spiral IDE sensor achieved a coefficient of determination (R2) of 0.9976 and a mean squared error (MSE) of 0.859, indicating good stability and repeatability over the tested period. Furthermore, comparison with a commercial moisture sensor showed that the proposed sensor reached a higher R2 value of 0.9995, exhibiting closer agreement with gravimetric measurements. These findings confirm that the developed sensor holds strong potential for in situ monitoring of soil moisture and can provide valuable technical support for landslide monitoring and prevention.