Electrosurgical instrument and method of use
An electrosurgical medical device and method for creating thermal welds in engaged tissue. In one embodiment, at least one jaw of the instrument defines a tissue engagement plane carrying a conductive-resistive matrix of a conductively-doped non-conductive elastomer. The engagement surface portions thus can be described as a positive temperature coefficient material that has a unique selected decreased electrical conductance at each selected increased temperature thereof over a targeted treatment range. The conductive-resistive matrix can be engineered to bracket a targeted thermal treatment range, for example about 60° C. to 80° C., at which tissue welding can be accomplished. In one mode of operation, the engagement plane will automatically modulate and spatially localize ohmic heating within the engaged tissue from Rf energy application—across micron-scale portions of the engagement surface.
1. An electrosurgical jaw structure for controlled application of energy to tissue, the structure comprising: first and second jaws movable between opened and closed positions, the jaws defining first and second engagement surface layers respectively for contacting tissue, the first engagement surface layer carrying a matrix material that defines a positively sloped temperature coefficient of resistance; a first conductor in contact with the matrix material, said first conductor coupled to an electrical energy source to define a first polarity therein during operation wherein a portion of current flowing through the matrix can flow to tissue; and a second conductor exposed in the second engagement surface layer, said second conductor coupled to said electrical energy source to define a second polarity therein during operation.
2. The electrosurgical jaw structure of claim 1 , further comprising:
a third conductor exposed in the first engagement surface layer spaced apart from the first conductor, said third conductor coupled to said electrical energy source to define said second polarity therein; wherein the matrix material is intermediate the first conductor and third conductor in the first engagement surface layer.
3. The electrosurgical jaw structure of claim 1 , wherein the first conductor is surrounded on at least two sides in the first engagement surface by the matrix material.
4. The electrosurgical jaw structure of claim 1 , wherein the first conductor comprises an island on a layer of the matrix material.
5. The electrosurgical jaw structure of claim 1 , further comprising matrix thermal expansion control means disposed within the interior of the jaw for controlling the dimensional envelope of the matrix material during energy application to tissue.
6. The electrosurgical jaw structure of claim 5 , wherein said matrix thermal expansion control means comprises a plurality of void volumes dispersed with the matrix material.
7. The electrosurgical jaw structure of claim 5 , wherein said matrix thermal expansion control means comprises at least one air gap disposed within an interior of the jaw proximate to said matrix material.
8. The electrosurgical jaw structure of claim 5 , wherein said matrix thermal expansion control means comprises at least one compressible material positioned within or proximate to the matrix, the at least one compressible material being compressible responsive to thermal expansion of the matrix material.
9. The electrosurgical jaw structure of claim 5 , wherein said matrix thermal expansion control means comprises at least one material with a negative temperature coefficient of expansion, the at least one negative temperature coefficient of expansion material positioned within or proximate to the matrix.