Electrosurgical jaw structure for controlled energy delivery
A working end of a surgical instrument that carries first and second jaws for delivering energy to tissue. In a preferred embodiment, at least one jaw of the working end defines a tissue-engagement plane that contacts the targeted tissue. The cross-section of the engagement plane reveals that it defines a surface conductive portion that overlies a variably resistive matrix of a temperature-sensitive resistive material or a pressure-sensitive resistive material. An interior of the jaw carries a conductive material or electrode that is coupled to an Rf source and controller. In an exemplary embodiment, the variably resistive matrix can comprise a positive temperature coefficient (PTC) material, such as a ceramic, that is engineered to exhibit a dramatically increasing resistance (i.e., several orders of magnitude) above a specific temperature of the material.
1. A working end of a surgical instrument for delivering energy to tissue, comprising:
paired first and second jaw members moveable between an open position and a closed position; and
at least one jaw including an electrode, a first body portion comprising an electrically conductive material having a temperature-sensitive variable resistance which increases with an increase in the temperature of the material for responding to the temperature of the tissue, and a second body portion comprising a conductive material, the second portion configured to be coupled to an Rf voltage source, the electrode and the second body portion configured to be coupled to separate poles of the Rf voltage source, wherein the first body portion is disposed between the second body portion and the electrode to control the passage of electrical current from the second body portion to the electrode and wherein said at least one jaw defines a surface engagement plane for engaging tissue, said engagement plane carrying an exposed surface of said first body portion.
2. The working end of claim 1 , said engagement plane carrying an exposed surface of said second body portion.
3. The working end of claim 1 , wherein said first body portion comprises a ceramic composition.
4. The working end of claim 1 , wherein said first body portion defines a switching range at which its electrical resistance substantially varies in a selected temperature range.
5. The working end of claim 4 , wherein said switching range falls between about 40° C. and 200° C.
6. A working end of a surgical instrument for delivering energy to tissue, comprising:
paired first and second jaw members moveable between an open position and a closed position; and
at least one jaw including an electrode adapted for contacting tissue, a first body portion comprising an electrically conductive material having a temperature-sensitive variable resistance which increases with an increase in the temperature of the material for responding to the temperature of the tissue, and a second body portion comprising a conductive material, the second portion configured to be coupled to an Rf voltage source, the electrode and the second body portion configured to be coupled to separate poles of the Rf voltage source, wherein the first body portion is disposed between the second body portion and to electrode to control the passage of electrical current from to second body portion to the electrode responsive to the temperature of contacted tissue and wherein said at least one jaw defines a surface engagement plane for engaging tissue, said engagement plane carrying an exposed surface of said first body portion.
7. The working end of claim 6 , said engagement plane carrying an exposed surface of said second body portion.
8. The working end of claim 7 , wherein said first body portion comprises a ceramic composition.
9. The working end of claim 6 , wherein said first body portion defines a switching range at which its electrical resistance substantially increases or decreases in a selected temperature range.
10. The working end of claim 9 , wherein said switching range falls between about 40° C. and 200° C.