Schematic plot of a system with a movable wall.

Optical readout of moisture in sand employing bipolar electrochemistry

B. Gupta, P. Suchomski, A. A. Melvin, S. Linfield, M. Opallo, W. Nogala

Electrochemistry Communications , 2022


The fast and wireless estimation of moisture in sand and other bulk materials usually requires high-tech instrumentation and computation. To overcome the complexity of such systems, we have employed bipolar electrochemistry as a fast, straightforward, and cost-effective method to wirelessly produce an optical signal. An electric field generated across moist sand is used to polarize an immersed light-emitting diode (LED), triggering an electrochemical reaction and causing a current to flow. Therefore, the bipolar activation of the LED by a threshold electric field creates an optically readable moisture sensor. The light emission intensity depends on two factors: the amount of moisture and the salt concentration. As two stimuli control the light emission, the signal can be considered as an AND logic gate, which is expected to open possibilities in wireless and user-friendly moisture sensors.

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