Systems and methods for in vivo detection of electrophysiological and electrochemical signals
Systems and methods for measuring electrophysiological and electrochemical signals in a portion of a body of a subject are provided. The structure includes an array of electrochemical sensors made of miniaturized multi-layer graphene, an array of electrophysiological electrodes, an integrated front-end readout circuit, and narrow silicon shafts with metal spines. The sensor arrays offer significantly higher sensitivity than conventional methods and enable simultaneous, multi-site measurement of chemical and electrophysiological. The front-end circuit contains features that allow significant improvement in detection of the resulting electrochemical current produced by the electrochemical sensing electrodes. The silicone probes allow measurements deep in the body. In one example, neuroprobes are provided that include an electrophysiological sensor and an amperometric or voltammetric electrochemical sensor for detecting electrochemical signals from neuromodulators such as dopamine in a portion of a brain of a subject.
1. A sensor assembly, comprising:
a substrate structured to be inserted into a portion of a body of a subject; and
a potentiometric electrochemical sensor positioned on the substrate, the potentiometric electrochemical sensor comprising a planar multilayer graphene and a field-effect transistor (FET) configured to: receive an activating signal for redox of an analyte included in a bodily fluid present in the portion of the body in contact with a surface of the planar multilayer graphene; and sense an electrochemical signal produced by the redox of the analyte, the electrochemical signal indicative of a concentration of the analyte, wherein the planar multilayer graphene has first and second end portions that are located directly on a surface of an insulator layer, and a middle portion, located laterally adjacent to, and between the first and second end portions, that is entirely spaced apart from, and suspended over, the FET by an air gap which is present entirely through the insulator layer.
2. The sensor assembly of claim 1 , wherein the insulator layer is adjacent to a top gate electrode of the FET.
3. The sensor assembly of claim 1 , wherein the substrate comprises a silicon-on-insulator (SOI) substrate, and wherein the FET is present in the silicon-on-insulator substrate.
4. The sensor assembly of claim 1 , wherein the FET comprises a silicon channel interposed between a top gate dielectric and a bottom gate dielectric.
5. The sensor assembly of claim 4 , wherein a thickness of at least one of the top gate dielectric, the bottom gate dielectric and the silicon channel is adjusted to tune an overall sensitivity of the sensor assembly.
6. The sensor assembly of claim 1 , wherein the multilayer graphene is configured to be polarized at a constant potential so as to cause the redox reaction with the analyte.
7. The sensor assembly of claim 6 , wherein the constant potential is applied with respect to a voltage applied to the source terminal of the FET such that the sensor assembly does not include a reference electrode.
8. The sensor assembly of claim 7 , wherein the redox reaction of the analyte generates excess electrons that alter electrical characteristics of the FET.
9. The sensor assembly of claim 1 , further comprising:
a front-end circuitry, comprising at least an amplifier, and an analog-to-digital conversion (ADC) circuitry, wherein the FET is connected to the front-end circuit, and wherein the ADC circuitry is configured to amplify and digitize an analog signal generated by the FET into a digital signal.
10. The sensor assembly of claim 1 , wherein the substrate contains a plurality of mechanical strength inducing spines positioned therein.