Device and method for detecting a sub-surface btex component

A device for wireless detection of a BTEX component in a soil saturated with water, the BTEX component and the water forming a liquid phase, the device comprising:

• an antenna adapted for receiving a radar signal and emitting a response radar signal;
• an enclosure permeable to the liquid phase;
• and a sensor located in the enclosure and comprising:
• a piezoelectric substrate comprising lithium tantalate, the substrate having a surface extending in a longitudinal direction,
• an interdigitated transducer located on the surface and electrically connected to the antenna for receiving an input electrical signal from the antenna and sending an output electrical signal to the antenna, the interdigitated transducer being adapted to convert the input electrical signal into surface acoustic waves in the longitudinal direction,
• a first mirror located on the surface and adapted for receiving a first part of the surface acoustic waves and producing a first echo towards the interdigitated transducer by mechanical reflection and/or re-emission of said first part of the surface acoustic waves,
• a second mirror located on the surface and adapted for receiving a second part of the surface acoustic waves and producing a second echo towards the transducer by mechanical reflection or re-emission of said second part of the surface acoustic waves,
• at least a first layer of a first polymer located on the surface between the transducer and the second mirror, the first polymer being adapted for reacting with the BTEX component so as to modify a travel speed of the second echo along the first layer, and
• at least a first guiding layer comprising a metal and/or a polymer, the first guiding layer being located on the surface between the transducer and the first mirror,
• the interdigitated transducer being adapted to convert the first echo and the second echo into at least part of the output electrical signal,
• the antenna being adapted for converting the output electrical signal into the response radar signal.