Abstract: Ultrasound-based wireless battery-free implantable sensors comprising a solution-gated field-effect transistor This disclosure relates to wireless battery-free implantable sensors for biomedical applications. Ultrasound-based wireless communication is proposed as an alternative to electromagnetic communication. The implantable sensor comprises a piezoelectric element and a variable impedance load whose value is a function of a physiological parameter of interest. The load is a solution-gated field-effect transistor (SG-FET), preferably a transistor with a graphene channel. The load is connected to the piezo-electric element for wireless communication with an external device. Experiments show that an ultrasound echo signal can be modulated by the gate voltage of the transistor and that the modulated signal can be transmitted through a propagation medium such a biological tissue.

Abstract: A microelectrode (2) for neural interfacing applications comprises a first substrate layer (4), a second attachment layer (6), and a third layer (8) forming the active part of the electrode (2) of which the material consists of synthetic diamond made in electrically conductive by doping with atoms chosen from boron, nitrogen and phosphorus atoms. The material of the third layer (8) is a textured material that comprises a compact assembly, in the form of a brush, of tubes (26) each comprising, in the form of at in least one peripheral outer layer, polycrystalline diamond made electrically conductive by doping. The tubes (26) are separated from each other at the first fixed ends (28) of same and project the free ends (30) of same away from the first and second layers (4, 6) in a direction that is substantially vertical relative to the extension plane (20) of the second layer (6). A method for producing said microelectrode is also described.