Surgical sealing surfaces and methods of use
Various embodiments provide compositions that exhibit positive temperature coefficient of resistance (PTCR) properties for use in thermal interactions with tissue—including thermal sensing and I 2 R current-limiting interactions. Embodiments also provide tissue-engaging surfaces having PTCR materials that provide very fast switching times between low resistance and high, current-limiting resistance. One embodiment provides a matrix for an electrosurgical energy delivery surface comprising a PTCR material and a heat exchange material disposed within an interior of the matrix. The PTCR material has a substantially conductive state and a substantially non-conductive state. The heat exchange material has a structure configured to have an omni-directional thermal diffusivity for exchanging heat with the PTCR material to cause rapid switching of the PTCR material between the conductive state and non-conductive state. Preferably, the structure comprises a graphite foam having an open cell configuration. The matrix can be carried by tissue contacting surfaces of various electrosurgical devices.
1. A matrix for an electrosurgical energy delivery surface, the matrix comprising:
a positive temperature coefficient of resistance (PTCR) material, the material having a substantially conductive state and a substantially non-conductive state; and
a heat exchange material disposed within an interior of the matrix, the heat exchange material having a structure configured to provide directional thermal diffusivity for exchanging heat with the PTCR material to cause rapid switching of the PTCR material between the conductive state and the non-conductive state.
2. The matrix of claim 1 , wherein the heat exchange material conducts heat from the PTCR material to cause rapid switching of the PTCR material between the conductive state and the non-conductive state.
3. The matrix of claim 1 , wherein the heat exchange material has a uni-directional thermal diffusivity.
4. The matrix of claim 1 , wherein the structure is a cellular structure, a non-amorphous structure or a crystalline structure.
5. The matrix of claim 1 , wherein the matrix is carried in a tissue-contacting surface of an electrosurgical device.
6. The matrix of claim 1 , wherein the matrix is carried in at least one jaw of an electrosurgical device.
7. The matrix of claim 1 , wherein the PTCR material is electrically insulated from the heat exchange material.
8. The matrix of claim 1 , wherein the heat exchange material comprises at least one graphite element.
9. The matrix of claim 1 , wherein at least a portion of the matrix comprises a graphite foam structure.
10. The matrix of claim 9 , wherein at least a portion of the graphite foam structure is a cellular structure, an open cell structure, a non-amorphous structure or a crystalline structure.
11. The matrix of claim 9 , wherein the graphite foam structure comprises a plurality of thermally conductive filaments.
12. The matrix of claim 11 , wherein at least a portion of the thermally conductive filaments are oriented to conduct heat in a unidirectional, bi-directional, or omni-directional manner.
13. The matrix of claim 1 , wherein the heat exchange material is coupled to a heat sink.
14. The matrix of claim 1 , wherein the heat exchange material comprises a phase change material.
15. The matrix of claim 1 , wherein the heat exchange material is a thermosiphon.
16. The matrix of claim 1 , wherein the heat exchange material has an electrically non-conductive polymer surface layer.