Ultrasonic surgical instruments

1. A surgical instrument, comprising:

a transducer configured to generate an acoustic standing wave of vibratory motion along a longitudinal axis, wherein the transducer comprises a piezoelectric stack positioned along the longitudinal axis, wherein the transducer is configured to resonate at a predetermined vibrational frequency, wherein a wavelength of the acoustic standing wave corresponds to the predetermined vibrational frequency, and wherein a length of the transducer is less than ½ of the wavelength of the acoustic standing wave; and

an end effector acoustically coupled to and extending distally from the transducer along the longitudinal axis;

wherein a sum of the length of the transducer and a length of the end effector is an integer multiple of ½ of the wavelength of the acoustic standing wave.

2. The surgical instrument of claim 1 , wherein the length of the transducer is greater than or equal to ¼ of the wavelength of the acoustic standing wave and less than ½ of the wavelength of the acoustic standing wave.

3. The surgical instrument of claim 1 , wherein the end effector comprises:

a waveguide acoustically coupled to and extending distally from the transducer; and

a blade coupled to and extending distally from the waveguide.

4. The surgical instrument of claim 3 , wherein the blade is positioned at a distance equal to ¼ of the wavelength of the acoustic standing wave from a distal most node of the end effector.

5. The surgical instrument of claim 1 , wherein the end effector comprises a proximal end and a distal end, and wherein the end effector is configured to gain an amplitude of the acoustic standing wave between the proximal end and the distal end.

6. The surgical instrument of claim 5 , wherein the end effector comprises a series of sections that alternate between sections of a first diameter and sections of a second diameter, and wherein each transition between a section of the first diameter to a section of the second diameter occurs at a zero-displacement node.

7. The surgical instrument of claim 1 , wherein the sum of the length of the transducer and the length of the end effector is substantially equal to 1 wavelength of the acoustic standing wave.

8. The surgical instrument of claim 1 , wherein the transducer is configured to generate an acoustic standing wave pattern with a predetermined amplitude at the predetermined vibrational frequency.

9. The surgical instrument of claim 1 , wherein the transducer comprises:

a transduction portion;

a first resonator portion extending proximally from the transduction portion; and

a second resonator portion extending distally from the transduction portion.

10. The surgical instrument of claim 9 , wherein a length of the first resonator portion and the second resonator portion is based on a thickness of the transduction portion, a density and modulus of elasticity associated with the first resonator portion and the second resonator portion, and the predetermined vibrational frequency of the transducer.

11. The surgical instrument of claim 1 , wherein the transducer further comprises a flange and a mass positioned along the longitudinal axis, and wherein the piezoelectric stack is located between the flange and the mass.

12. The surgical instrument of claim 11 , wherein the length of the transducer is greater than ¼ of the wavelength and less than ½ of the wavelength of the acoustic standing wave, and wherein the flange is positioned at a node of the transducer.

13. A surgical instrument, comprising:

a transducer configured to provide a wave of longitudinal vibratory motion along a longitudinal axis, wherein the transducer comprises a piezoelectric stack positioned along the longitudinal axis, wherein the transducer is configured to resonate at a predetermined frequency, wherein a wavelength of the wave corresponds to the predetermined frequency, and wherein a length of the transducer is greater than or equal to ¼ of the wavelength of the wave and less than ½ of the wavelength of the wave; and

an end effector coupled to and extending distally from the transducer along the longitudinal axis;

wherein a sum of the length of the transducer and a length of the end effector is an integer multiple of ½ of the wavelength of the wave.

14. The surgical instrument of claim 13 , wherein the end effector comprises a proximal end and a distal end, and wherein the end effector is configured to gain an amplitude of the wave between the proximal end and the distal end.

15. A surgical instrument, comprising:

a transducer configured to generate an acoustic wave of vibratory motion along a longitudinal axis at a predetermined frequency, wherein a length of the transducer is less than ½ of a wavelength of the acoustic wave; and

an end effector coupled to a distal end of the transducer, wherein the end effector comprises:

a waveguide coupled to and extending distally from the transducer; and

a blade coupled to and extending distally from the waveguide;

wherein a sum of the length of the transducer, a length of the waveguide, and a length of the blade is an integer multiple of ½ of the wavelength of the acoustic wave.

16. The surgical instrument of claim 15 , wherein the end effector comprises a proximal end and a distal end, and wherein the end effector is configured to gain an amplitude of the acoustic wave between the proximal end and the distal end.

17. The surgical instrument of claim 16 , wherein the end effector comprises a series of sections that alternate between sections of a first diameter and sections of a second diameter, and wherein each transition between a section of the first diameter to a section of the second diameter occurs at a zero-displacement node.

18. The surgical instrument of claim 15 , wherein the sum of the length of the transducer, the length of the waveguide, and the length of the blade is substantially equal to 1 wavelength of the acoustic wave.