Graphene Solution‐Gated Field‐Effect Transistor for Ultrasound‐Based Wireless and Battery‐Free Biosensing

Abstract The development of wireless and battery‐free sensors for biomedical applications is a fast growing research and industrial field. It promises to greatly improve the patient's comfort during the diagnosis phase, but also in the treatment of chronic diseases. While the standard technologies are based so far on electromagnetic waves, ultrasonic powering and communication is offering perspectives to further reduce the size of the sensor in order to develop minimally invasive electronic implants. Wireless and battery‐free ultrasound‐based devices for healthcare monitoring comprise a piezoelectric element for the powering and communication, and a variable shunt load that varies according to a physiological parameter of interest. The changes in the load modify the acoustic reflectivity of the piezoelectric element, which can be detected using a pulse‐echo protocol. In the present study, the use of graphene solution‐gated field‐effect transistor is introduced as a new type of shunt load. Using an mm‐sized device, it is shown that the amplitude of an ultrasonic wave that reflects on the piezoelectric component is modulated by the voltage applied on the gate of the transistor both in physiological medium and biological tissue. This study sets the basis toward a new type of ultrasound‐based wireless and battery‐free biosensors.