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 method of applying controlled energy to treat tissue, the method comprising:
engaging tissue with an electrosurgical surface, the surface coupled to a matrix comprising a positive temperature coefficient of resistance (PTCR) material and a heat exchange material disposed within an interior of the matrix, the PTCR material having a substantially conductive state and a substantially non-conductive state;
delivering Rf current to tissue so as to ohmically heat tissue; and
modulating the delivery of Rf current to tissue wherein the Rf current flows at least partly through the matrix and the heat exchange material removes heat from the PTCR material to substantially prevent tissue charring or arcing in tissue.
2. The method of claim 1 , further comprising:
producing a substantially uniform thermal effect in tissue.
3. The method of claim 2 , wherein the substantially uniform thermal effect is at least one of tissue welding, tissue sealing, tissue seal strength, protein denaturation or protein fusion.
4. The method of claim 1 , wherein heat is conducted uni-directionaly from the matrix.
5. The method of claim 1 , wherein heat is conducted multi-directionaly from the matrix.
6. The method of claim 1 , wherein the heat exchange material acts as a heat sink.
7. A method of applying controlled energy to treat tissue, the method comprising:
engaging tissue with an electrosurgical energy delivery surface including a matrix of a positive temperature coefficient of resistance (PTCR) material and a heat exchange material disposed within an interior of the matrix;
engaging tissue with the surface;
delivering Rf energy to tissue so as to ohmically heat at least a portion of the engaged tissue; and
utilizing the heat exchange material to remove heat from the PTCR material to cause rapid switching of the PTCR material between substantially conductive and substantially non-conductive states.
8. The method of claim 7 , wherein the rapid switching substantially prevents tissue charring or arcing in tissue.
9. The method of claim 7 , further comprising:
utilizing the switching to spatially modulate the delivery of Rf energy to tissue to produce a substantially uniform thermal effect in tissue.
10. The method of claim 9 , wherein the substantially uniform thermal effect is at least one of tissue welding, tissue sealing, tissue seal strength, protein denaturation or protein fusion.
11. A method of delivering energy to treat tissue, the method comprising:
engaging tissue with an electrosurgical energy delivery surface including a matrix comprising a positive temperature coefficient of resistance (PTCR) material and a heat exchange material disposed within an interior of the matrix, the PTCR material having a substantially conductive state and a substantially non-conductive state;
delivering Rf energy to tissue so as to ohmically heat tissue in a target tissue volume;
spatially modulating the delivery of Rf energy to tissue utilizing the heat exchange material to exchange heat with the PTCR material to cause rapid switching of the PTCR material between the substantially conductive and substantially non-conductive states; and
producing a substantially uniform thermal effect in the target tissue volume.
12. The method of claim 11 , wherein the target tissue volume includes at least one of soft tissue, collagen containing tissue, vascular tissue, muscular tissue, fascia tissue or dermal tissue.
13. The method of claim 11 , wherein the substantially uniform thermal effect is at least one of tissue welding, tissue sealing, tissue seal strength, protein denaturation or protein fusion.
14. The method of claim 11 , further comprising:
spatially modulating the delivery of RF energy to prevent at least one of charring or arcing in tissue.
15. The method of claim 11 , further comprising:
spatially modulating the delivery of RF energy to a blood vessel to create a high strength fluidic seal in the vessel wall.