Neurostimulator
Methods and devices for stimulating nerves are disclosed. In one embodiment adapted for stimulating excitable tissue, the invention includes drive circuitry, an acoustic transducer and a pair of electrodes.
1. A neurostimulator, comprising:
drive circuitry;
an acoustic transducer connected to the drive circuitry; and
an implantable stimulator having a piezoelectric chip and a pair of electrodes;
where the drive circuitry is configured to drive the acoustic transducer to generate a pressure wave;
where the acoustic transducer is positioned to direct the pressure wave at the implantable stimulator and generate a current between the pair of electrodes;
where the piezoelectric chip comprises
a piezoelectric element having at least two opposite surfaces;
a diode; and
a biocompatible coating surrounding the piezoelectric element and the diode.
2. The neurostimulator of claim 1 , wherein the piezoelectric chip includes lead zirconate titanate (PZT).
3. The neurostimulator of claim 1 , where in the piezoelectric chip includes polyvinylidene fluoride (PVDF).
4. The neurostimulator of claim 1 , wherein the drive circuitry further comprises:
a pulse generator;
a function generator connected to the pulse generator; and
amplifier circuitry connected to the function generator.
5. The neurostimulator of claim 4 , wherein the amplifier circuitry comprises:
a drive amplifier; and
a RF amplifier.
6. A neurostimulator, comprising:
drive circuitry;
an acoustic transducer connected to the drive circuitry; and
an implantable stimulator having a piezoelectric chip and a pair of electrodes;
where the drive circuitry is configured to drive the acoustic transducer to generate a pressure wave;
where the acoustic transducer is positioned to direct the pressure wave at the implantable stimulator and generate a current between the pair of electrodes; and
further comprising additional piezoelectric chips,
where each of the piezoelectric chips has a different resonant frequency; and
where the drive circuitry is configured to drive the acoustic transducer at the resonant frequency of one of the piezoelectric chips.
7. A method of stimulating tissue, comprising:
applying high frequency ultrasound signals to body tissue;
applying electrical stimulation to the body tissue using a pair of electrodes; and
where the high frequency ultrasound signal inhibits the generation of a compound action potential in a nerve fiber.
8. The method of claim 7 , where the electrodes are located external to a subject.
9. The method of claim 7 , where the electrodes are internal to a subject and where applying electrical stimulation to the body tissue using a pair of electrodes comprises:
producing drive electrical signals in a drive circuitry;
emitting pressure waves with an acoustic transducer in response to the drive electrical signals; and
converting the pressure waves into stimulation electrical signals in an implantable stimulator, where the implantable stimulator includes a piezoelectric chip and a pair of electrodes.
10. The method of claim 9 , where one of the drive electrical signals is a pulse.
11. The method of claim 9 , where the high-frequency ultrasound signal occurs before converting the pressure waves into stimulation electrical signals.
12. The method of claim 9 , where the high frequency ultrasound signal is a pulse having a length of between 300 μs and 10 ms.
13. The method of claim 9 , where the high frequency ultrasound signal is a series of pulses with a repetition rate between 1 pulse per second and 10 pulses per second.
14. The method of claim 9 , where the implantable stimulator is placed in close proximity to a nerve in a patient.
15. The method of claim 7 , where the high frequency ultrasound signal provides stimulation to a tissue.
16. The method of claim 7 , further comprising stimulating a pudental nerve with the electrical stimulation.