Electrosurgical instrument having a coated electrode utilizing an atomic layer deposition technique

[0001] 1. Technical Field

[0002] The present disclosure relates generally to an electrosurgical system for treating tissue. More particularly, the present disclosure is directed to an electrosurgical instrument having a coated electrode utilizing an atomic layer deposition technique.

[0003] 2. Background of Related Art

[0004] Electrosurgery involves the application of electricity and/or electromagnetic energy to cut, dissect, ablate, coagulate, seal, or otherwise treat biological tissue during a surgical procedure. Additionally, certain electrosurgical modes invoke the application of electrosurgical energy through a compressed vessel secured between two electrodes to seal the vessel without significant cutting during the sealing process. Electrosurgical cutting, on the other hand, includes applying an electrical spark to tissue in order to produce a cutting or dividing effect. Blending includes the function of cutting combined with the production of a hemostasis effect.

[0005] Generally, electrosurgery utilizes an energy generator, an active electrode and a return electrode. The energy generator generates an electromagnetic wave (commonly referred to as “electrosurgical energy”), typically above 100 kilohertz to avoid muscle and/or nerve stimulation between the active and return electrodes when applied to tissue. During electrosurgery, current generated by the electrosurgical generator is conducted through the patient's tissue disposed between the two electrodes. The electrosurgical energy is returned to the electrosurgical source via a return electrode pad positioned under a patient (e.g., a monopolar system configuration) or a smaller return electrode positionable in bodily contact with or immediately adjacent to the surgical site (e.g., a bipolar system configuration). The current causes the tissue to heat up as the electromagnetic wave overcomes the tissue's impedance.

[0006] As mentioned above, vessel sealing invokes the application of electrosurgical energy thorough a compressed vessel secured between two electrodes to seat the vessel without significant cutting during the sealing process. The tissue undergoes changes by the applied electrosurgical energy including tissue in direct contact with the electrodes. The tissue in contact with the electrodes sometimes sticks to the electrodes and so called “eschar” can build up on the electrodes. The eschar must be cleaned or sticking will worsen. Eschar increases the impedance between the electrode and the tissue being treated thus reducing the efficiency of the electrosurgical energy transfer. Also, overall tissue impedance is typically monitored during sealing and the build up of eschar can contribute to higher impedance measurements resulting in increased sealing time. Therefore, a non-stick coating is typically applied to the electrodes to mitigate these effects and to reduce stiction.

[0007] The present disclosure relates generally to an electrosurgical system for treating tissue. More particularly, the present disclosure is directed to an electrosurgical instrument having electrode with a coating formed using an atomic layer deposition technique. An ALD coating can be applied to any electrode surface including monopolar electrosurgical devices or bipolar forceps used for cutting, coagulating, ablating. Additionally, an ALD coating may be applied to a return electrode of an electrosurgical system.

[0008] In an embodiment of the present disclosure, an electrosurgical instrument includes one or more support members and an electrode. The electrode is disposed on a support member. A coating is disposed (at least partially) on the electrode. The coating includes a seed layer and an ALD layer, which may be either hydrophobic or hydrophilic.

[0009] In another embodiment of the present disclosure, the seed layer is also formed using atomic layer deposition. The seed layer may be conductive or insulative; and additionally or alternatively, the seed layer may be ceramic. The seed layer can include Al₂O₃ formed from sequential reactions shown below as reactions (I) and (II).
AlOH*+Al(CH₃)₃→AlO−Al(CH₃)*₂+CH₄  (I)
AlCH*₃+H₂O→AlOH*+CH₄  (II)

[0010] The ALD layer may be formed using one or more precursors such as a chlorosilanes precursor, a non-chlorinated hydrophobic precursor, an alkylaminosilane precursor, a chlorosilane precursor, a bis-alkylaminosilane precursor and/or a tris-alkylaminosilane precursor.

[0011] In yet another embodiment, the seed layer includes titanium nitride and the ALD layer includes Zn₁₉Al₅O₂. Alternatively, either the seed layer or the ALD layer includes Zn₁₉Al₅O₂. Additionally or attentively, the seed layer includes about 5% of titania-alumina-oxide and the ALD layer includes about 90% titania. The seed layer may have surface functional groups, such as surface hydroxyl groups such that the function groups react with the hydroxyl groups to form the ALD layer. The ALD layer may be formed from Tridecafluoro-1,1,2,2-tetrahydrooctylmethyl-bis(dimethylamino)silane(FOMB(DMAS)S, C₈F₁₃H₄(CH₃)Si(N(CH₂)₂)₂).

[0012] In yet another embodiment of the present disclosure, a method of coating includes: providing an electrosurgical instrument; coating an electrode of the electrosurgical instrument with a seed layer; and coating the seed layer with an ALD layer such that the ALD layer is hydrophobic or hydrophilic. The method may also include applying first and second precursors to the electrode such that the second precursor reacts with the first precursor to form (or partially form) the seed layer. The first precursor may be trimethylaluminum (Al(CH₃)₃,TMA) and the second precursor may be H₂O. Additionally or alternatively, the method includes applying a precursor to the seed layer forming the ALD layer, such as Tridecafluoro-1,1,2,2-tetrahydrooctylmethyl-bis(dimethylamino)silane(FOMB(DMAS)S, C₈F₁₃H₄(CH₃)Si(N(CH₂)₂)₂).

[0019] Particular embodiments of the present disclosure are described hereinbelow with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail.

[0020] Referring to the drawings, FIG. 1A is a perspective-view of an electrosurgical instrument 100 having coated electrodes 102 and 104 in accordance with the present disclosure. Although the coating is discussed with regards to electrosurgical forceps, it is in the purview of one of ordinary skill in the art to extend the coating system and method to other instruments, including: monopolar or bipolar electrosurgical instruments, return pads, RF ablation probes, microwave surgical instruments, and the like.

[0021] Electrosurgical instrument 100 may seal vessels using electrosurgical energy and includes jaw members 106 and 108 that are movable relative to each other about pivot 110 to grasp tissue. Jaw member 106 supports coated electrode 102 and jaw member 108 supports coated electrode 104. Jaw member 106 defines a channel 112 allowing reciprocating actuation of a cutting device (not shown), such as a blade or cutting electrode. Jaw member 108 may also include a channel, which is not explicitly shown in FIG. 1A.

[0022] During an electrosurgical procedure, a blood vessel (not shown) is placed between jaw members 106 and 108 while jaw member 106 is in an “open” position (as shown in FIG. 1), that is, jaw member 106 is spaced apart from jaw member 108. The surgeon actuates one or more suitable mechanical linkages (not shown) causing jaw member 106 to pivot about pivot pin 110 towards jaw member 108, thereby grasping the vessel. The surgeon thereafter can activate an electrosurgical generator (not shown) causing electrosurgical energy to flow between coated electrodes 102 and 104 through the grasped vessel. The tissue of the vessel heats up as the electrosurgical energy overcomes impedance of the tissue in the vessel. The electrosurgical energy seals the vessel thus stopping blood flow therethrough.

[0023] During vessel sealing, tissue tends to stick to non-coated electrodes and tissue eschar tends to buildup on the non-coated electrodes, which detrimentally affects the overall seal quality due to the eschar increasing the impedance between electrodes. The increase in impedance may provide unreliable feedback to the electrosurgical generator. By coating electrodes with a non-stick coating, many of these effects are mitigated and a better seal results. According to the teaching of the present disclosure, a non-stick coating is deposited (or formed) on electrodes utilizing atomic layer deposition.

[0024] Atomic Layer Deposition (referred to herein as “ALD”) is a gas phase chemical process used to create thin coatings. The majority of ALD reactions use two chemicals, typically called precursors to form these coatings. These precursors react individually with each surface in a repeatable and sequential manner. Film growth is controlled by exposing the precursors to a growth surface repeatedly. Generally, ALD is a self-limiting, sequential surface chemistry that deposits conformal films or coatings onto substrates of varying compositions. ALD growth is based on surface reactions making atomic scale deposition control possible.

[0025] Referring to the drawings, FIG. 1B is a cross-sectional view along line 1B-1B of the electrosurgical instrument 100 as shown in FIG. 1A in accordance with the present disclosure. More particularly, FIG. 1B shows a cross-sectional view of jaw member 106. Coated electrode 102 is secured to a base 114 of jaw member 106 using a securing layer 116. Securing layer 114 is formed from any sufficient material for securing coated electrode 102 to support structure 114, such as glue, ceramic, silicon, epoxy, and the like. Additionally or alternatively, a securing device (not shown) may be used to secure coated electrode 102 to support structure 114, such as an oversold, a fastener, a clip, a screw, and the like. Coated electrode 102 includes an electrode 118, a seed layer 120, and an ALD layer 122. Coated electrode 102 may be capacitive and/or non-capacitive, and may have any sufficient operational bandwidth, e.g., from DC to radio frequencies.

[0026] Seed layer 120 may be conductive or insulative, and may be a ceramic. Seed layer 120 is formed on electrode 118 using atomic layer deposition. In one embodiment, seed layer 120 may be Al₂O₃ formed from one or more reactions using precursors. The overall binary reaction is 2Al(CH₃)₃+3H₂0→Al₂0₃+6CH₄ and is divided into two reactions shown as reactions 1 and 2 below:
AlOH*+Al(CH₃)₃→AlO−Al(CH₃)₂*+CH₄  (1)
AlCH₃*+H₂0→AlOH*+CH₄  (2)

[0027] The asterisk denotes the surface species. These and other related reactions are discussed in an article in The Journal of Micromechanics and Microengineering, entitled “Conformal hydrophobic coatings prepared using atomic layer deposition seed layers and non-chlorinated hydrophobic precursors” by Herrmann, DelRio, Bright and George, which is hereby incorporated by reference in its entirety. Electrode 118 has surface hydroxyl groups in such that a precursor reacts therewith, such as trimethylaluminim (Al(CH₃)₃,TMA). Additionally or alternatively, the ALD layer 122 includes titanium nitride. The seed layer may also contain about 5% of titania-alumina-oxide.

[0028] Coated electrode 102 also includes an ALD layer 122. The ALD layer 122 is hydrophobic if seed layer 120 is insulative because water reduces the conductivity near coated electrode 102 or the ALD layer 122 is hydrophilic if seed layer 120 is conductive because increased conductivity is desirable. The ALD layer 122 is formed using one or more precursor, such as a chlorosilanes precursor, a non-chlorinated hydrophoblic precursor, an alkylaminosilane precursor, a chlorosilane precursor, a bis-alkylaminosilane precursor and a tris-alkylaminosilane precursor. Additionally or alternatively, ALD layer 122 is a ceramic.

[0029] After seed layer 120 is disposed on electrode 118 the ALD layer 122 is formed on the seed layer 120 by reacting with function groups of seed layer 120, such as surface hydroxyl groups on seed layer 120 which react with a precursor to form ALD layer 122. The ALD layer 120 may be formed from Tridecafluoro-1,1,2,2-tetrahydrooctylmethyl-bis(dimethylamino)silane (FOMB(DMAS)S, C₈F₁₃H₄(CH₃)Si(N(CH₂)₂)₂). Additionally or alternatively, the ALD layer 120 may be about 90% titania. ALD layer 122 prevents and or mitigates the effects of tissue sticking to the surface of coated electrode 102 because of the ALD's chemical properties.

[0030] Referring to the drawings, FIGS. 2A-2E shows several electrosurgical instruments having a coated electrode. Although in FIG. 1 electrosurgical forceps were described as having a coating formed using atomic layer deposition, FIGS. 2A through 2E show several additional electrosurgical instruments that are coated using atomic layer deposition. Instruments 200 through 208 are shown and include support members 220 thorough 228. Each of support members 220 through 228 includes one of electrodes 210 through 218, respectively. Electrodes 210 through 218 may each either be hydrophilic or hydrophobic and may include a seed layer.

[0031] Referring to the drawings, FIGS. 3A-3B is an illustration 300 of various stages of disposing a coating on an electrode 118′ using atomic layer deposition in accordance with an embodiment of the present disclosure. Illustration 300 includes stages 302 through 320. Stage 302 shows electrode 118′ having a reacting surface 322. During stage 304 a precursor A is added. Precursor A reacts with reacting surface 322 resulting in electrode 118′ as shown in stage 306. Precursor A reacts with reacting surface 322 forming a monolayer. The reactions occurring during stage 304 are self-limiting. Various molecules will be produced during the reaction and are represented as products 324. During stage 308, products 324 and excess A are flushed using a non-reacting gas.

[0032] In stage 310, a precursor B is added which reacts to surface 326. Stage 312 illustrates the results, that is, products 328 remain and electrode 118′ has a reacting surface 330. Stage 214 flushes excess gases of precursor A and products 328. Note that stages 304 through 314 may be repeated several times. For example, stages 304 through 314 may be repeated until electrode 118′ has a seed layer of a predetermined thickness. After a predetermined number of cycles, stage 316 shows the resulting electrode 118′ with seed layer 332 having a reacting surface 334. Stage 218 adds precursor C, which thus reacts with reacting surface 334 forming the ALD layer 336 and products 338 as shown in stage 320. The ALD may be either hydrophobic or hydrophilic.

[0033] Referring to the drawings, FIG. 4 is a flow chart of a method 400 of coating an electrode using utilizing atomic layer deposition in accordance with an embodiment of the present disclosure. Method 400 includes steps 402 through 408. Step 402 provides an electrosurgical instrument having an electrode. Step 404 applies a first precursor to the electrode. Step 406 applies a second precursor to the electrode. Steps 406 and 406 may be repeated as desired to control the thickness of the electrode coating. After the appropriate thickness of the seed layer is achieved, step 408 applies another precursor forming the ALD layer.

[0034] While several embodiments of the disclosure have been shown in the drawings and/or discussed herein, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.