Patent Description:
Intraluminal medical devices have various structures depending on the location of their intended deployment within the body and the intended method of treatment using the devices. Intraluminal devices generally include a very slender, i.e., very small in cross section, and flexible, tube that can be inserted into and guided through a body lumen such as an artery or a vein, or a bodily passageway such as a throat, a urethra, a bodily orifice or some other anatomical passage. Examples of such medical devices include syringes, endoscopes, catheters, guide wires and other surgical instruments.

For example, guide wires are commonly used to navigate vessels to reach a target lumen, bodily passageway, bodily orifice or anatomical passage. Once the guide wire reaches the target location within a body, a catheter, stent or other medical device may be guided to the target location by movement over or along the guide wire.

Conventional guide wires improve access to treatment locations within the patient's body but offer poor directional control because of their high flexibility. The flexibility is required to allow the guidewire to move through tortuous pathways in a lumen or passage. However, this same flexibility results in the aforementioned poor control of the direction or path the distal end of the guidewire will take when it is pushed at its proximal end. Thus, there is a need for improved guide wires having better steering control.

<CIT> discloses a guidewire system having a highly flexible core <NUM> of continuous stiffness, which is surrounded by a stiffening member <NUM>. The stiffening member includes a tubular electroactive portion <NUM>, and an inner electrode <NUM> and an outer electrode <NUM> on opposed inner and outer sides of the tubular electroactive portion. Application of electrical energy to the electrodes <NUM> and <NUM> is used to change the stiffness of the device where the stiffening member is present. Both of an inner and an outer electrode must be part of an electrical circuit to change the stiffness of the device at the stiffening member.

<CIT> discloses a flexible, narrow medical device (a micro-catheter or a guidewire) that is controllably moved and steered through lumens of a body. The medical device includes an electrically-actuatable bendable portion at a distal end thereof, which may be provided by a polymer electrolyte layer, electrodes distributed about the polymer electrolyte layer, and electrical conduits coupled to the electrodes, such that the polymer electrolyte layer can be deformed asymmetrically in response to an electrical signal through one or more conduits. The elongate, flexible portion of the micro-catheter includes an inner member, a reinforcing mesh and an outer member. The elongate flexible portion and the bendable portion are surrounded by an outer sleeve <NUM> that covers the tubular elongate flexible portion <NUM> and the bendable portion <NUM>.

<CIT> discloses an elongate device for introduction into a body lumen having a body extending in a longitudinal direction and having at least two skeletal members which are substantially aligned in the longitudinal direction, and at least one electroactive polymer material, which changes volume upon electrical activation thereof. The electroactive polymer portion is arranged to control a distance between two longitudinally spaced-apart portions of the skeletal members). The electroactive polymer portion is a part of the guidewire shaft and is not a separate bending portion.

<CIT> discloses a guidewire having a helical groove therein into which one or more electrical conductors can be recessed. These conductors are provided for, for example, pacing, sensing, defibrillating and monitoring or treating electrical phenomena within the body from outside the body.

<CIT> discloses a steerable guide wire including one or more electroactive polymer layers, wherein each electroactive polymer layer is disposed between a first electrode and a plurality of second electrodes.

<CIT> discloses a guidewire or section thereof having a plurality of contiguous tapered segments having taper angles that are configured to produce a linear change in stiffness over a longitudinal portion of the device.

<CIT> discloses a remotely steerable guidewire, catheter or insertable active implement, which uses smart materials such as piezoelectrics for controlling its motions inside the body via control inputs applied from outside the body.

Embodiments of the steerable intraluminal medical device provide improved steering control and intra-body positioning of an actuation part (e.g., a guidewire) of a medical device wherein the actuation part is adapted to be introduced into a lumen or into a bodily passage or lumen of a body and manipulated while the actuation part is being pushed inwardly of the body for movement into and through the lumen or bodily passage to dispose a distal end of the actuation part of the medical device at a desired anatomical location within the body. Embodiments of the medical device provide more precise control of movement and positioning of one or more manipulatable microsurgical components disposed at the distal, leading, end, of the actuation part of the medical device for performing a surgical procedure or other medical operation at the desired location within the body.

One embodiment of a medical device may have an actuation part in a guidewire form to be moved into or through a lumen or a bodily passage. The medical device comprises a slender, elongate and flexible portion having a distal end and a proximal end, and an ionic electroactive polymer actuator comprising a polymer electrolyte member disposed adjacent to the distal end of the elongate and flexible portion. One embodiment of the elongate and flexible portion may further comprise a core extending from the proximal end to the distal end, and a sleeve surrounding the core. The ionic electroactive polymer actuator, as will be discussed in greater detail below, is an actuator comprising a polymer electrolyte member in which cations are free to migrate in response to an electrical field imposed thereon. The electrical field is provided through energization of a plurality of distributed electrodes disposed and spaced about a circumference of the polymer electrolyte member. The plurality of distributed electrodes are one of embedded in, deposited on, and secured against at least a portion of at least a surface of the polymer electrolyte member. Each of the plurality of electrodes may be connected to a source of electrical potential through one or more electrically-conductive wires such as, for example, a metal wire extending over the core of the elongate, flexible portion and having a proximal end coupled to the source of electrical potential and a distal end coupled to the electrode. Selective electrical energization of one or more, but not all, of the plurality of electrodes causes the polymer electrolyte member to deform asymmetrically as a result of contracting along a side or portion of the polymer electrolyte member and/or swelling along a side or portion of the polymer electrolyte member.

In some embodiments, the outer surface of the core can be linearly tapered, tapered in a curvilinear fashion, or tapered in a step-wise fashion from the distal end of the elongate, flexible, portion to form a reduced thickness, reduced width, or reduced diameter end. The angle of any such tapered end can vary, depending upon the desired flexibility characteristics. The length of the tapered end may be selected to obtain a more gradual (longer taper length) or less gradual (shorter taper length) transition in stiffness. In some embodiments, the tapered end may include a tapering outer diameter distally so that a portion of the core is reduced in cross section and thus can be embedded into the polymer electrolyte member. In some embodiments, the core has a solid cross-section. But in some alternative embodiments, the core can have a hollow cross-section. For example, in some embodiments, an inner lumen is provided and formed longitudinally within the core from the proximal end to the distal end thereof. In other embodiments, the core may comprise a metallic material and couple to at least one of the plurality of electrodes to serve as an additional electrically-conductive conduit.

In some embodiments, the sleeve may extend from the distal end of the elongate, flexible portion to surround at least a portion of the ionic electroactive polymer actuator. For example, the sleeve may surround one of the electrodes, the polymer electrolyte member, or a combination thereof.

The electrically-conductive wires are interconnected with the elongate and flexible portion via various means, techniques and/or structures. For example, but not by way of limitation, in one embodiment, each of the electrically-conductive wires is disposed linearly or parallelly along an exterior surface of the core, and they are spaced thereon from each other circumferentially. In an exemplary embodiment, a plurality of grooves are formed linearly, and spaced from each other circumferentially, inwardly of the exterior surface of the core, each groove receiving one of the electrically-conductive wires therein, respectively. In other embodiments, each of the plurality of electrically-conductive wires is helically or interweavingly wrapped around the core. Alternatively, in some embodiments, the electrically-conductive wires may be secured between the sleeve and the core and further be secured to at least a portion of the ionic electroactive polymer actuator. In other embodiments, the electrically-conductive wires may pass through the core, e.g. being secured or embedded through the core when the core has a solid cross-section. Alternatively, where the core has a hollow cross-section, the electrically-conductive wires may pass through the inner lumen defined within the core as described above.

To insulate the electrically-conductive wires from the elongate and flexible portion and the ionic electroactive polymer actuator except where contact therewith is desired, each of the plurality of electrically-conductive wires may further comprise an insulation coating thereon. The material of the insulation coating may comprise for example, but is not limited to, ceramic, PTFE, nylon, polyimide, polyester or a combination thereof.

In some embodiments, the polymer electrolyte member may comprise a polymer host and an electrolyte as solvent. The polymer may comprise, but is not limited to, fluoropolymers and intrinsically conducting polymers. In an exemplary embodiment, the fluoropolymers may comprise perfluorinated ionomers, polyvinylidene difluoride (PVDF) or a co-polymer thereof (e.g. Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), but are not limited to these polymers. In another exemplary embodiment, the intrinsically conducting polymers may comprise, but are not limited to, polyaniline (PANI), polypyrrole (Ppy), poly(<NUM>,<NUM>-ethylenedioxythiophene) (PEDOT), poly(p-phenylene sulfide) (PPS) or the combination thereof. In yet another embodiment, the electrolyte may be water or an ionic liquid. An exemplary example of the ionic liquid may include, but is not limited to, <NUM>-ethyl-<NUM>-methylimidazolium tetrafluoroborate (EMI-BF4), <NUM>-ethyl-<NUM>-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-TFSI), <NUM>-ethyl-<NUM>-methylimidazolium trifluoromethanesulfonate (EMITf) or the combination thereof.

In some embodiments, each of the electrodes may comprise one of platinum, gold, a carbon-based material and a combination thereof. Exemplary examples of the carbon-based material may comprise, but are not limited to, one of carbide-derived carbon, carbon nanotube(s), graphene, a composite of carbide-derived carbon and polymer electrolyte member, and a composite of carbon nanotube(s) and polymer electrolyte member.

In one embodiment of the medical device, the ionic electroactive polymer actuator may comprise a plurality of individual, and electrically isolated from one another, electrodes which are angularly distributed about at least a surface of the polymer electrolyte member. In one embodiment of the medical device, the ionic electroactive polymer actuator is included in a bendable portion at the distal end of an actuation part (e.g., a guidewire) of the medical device. For example, but not by way of limitation, the bendable portion of the medical device, in one embodiment, comprises three angularly-distributed electrodes that are separated, at their centerlines, each one from the others by about <NUM> degrees (<NUM> radians). As another example, but not by way of limitation, the bendable portion of the medical device may comprise eight angularly-distributed electrodes that are separated, at their centerlines, by about <NUM> degrees (<NUM> radians) from each other. It will be understood that each of the plurality of electrodes occupies a portion of the circumferential span around the surface of the polymer electrolyte member, and that the "angular separation" may therefore be stated in terms of the centerlines of the electrodes instead of in terms of the adjacent edges of the electrodes, which will be much closer to the adjacent edge of the adjacent electrodes than will be their adjacent centerlines. In some embodiments of the medical device, the electrodes are spaced in a manner to provide a substantial gap between adjacent electrodes.

In some embodiments, electrically-conductive wires are directly interconnected (e.g. are integrated and embedded) to electrodes using various conventional techniques such as soldering, crimping, stapling, pinching, welding, conductive adhesive (e.g., using conductive epoxy), and the like. Alternatively, in some embodiments, electrically-conductive wires are indirectly interconnected to the electrodes through an intervening conductive bridge. In an exemplary embodiment, the conductive bridge extends between a surface of the polymer electrolyte member and at least one of the electrodes to serve as a conductive interface to connect the electrically-conductive wires to the electrodes and allow movement therebetween without negatively impacting the electrical connection therebetween.

In some embodiments, the ionic electroactive polymer actuator can be configured in any possible configuration to provide two degrees of freedom of bending motion. For example, four electrodes are circumferentially distributed by an equal angular spacing of their centerlines about the surface of the polymer electrolyte member. In some embodiments, the ionic electroactive polymer actuator can be configured in any possible configuration to provide one degree of freedom in bending motion. In one exemplary embodiment, the polymer electrolyte member may be a right circular cylindrical, or other cross section, rod or have another rod-like shape, and two electrodes are circumferentially distributed by equal angles about the surface of the polymer electrolyte member. In another exemplary embodiment, the polymer electrolyte member may have a rectangular shape and define a top surface and a corresponding bottom surface and two electrodes are circumferentially distributed about the top surface and the bottom surface of the polymer electrolyte member symmetrically to form a sandwich structure where the electrodes sandwich the polymer electrolyte member therebetween.

The appended illustrative drawings provide a further understanding of embodiments and are incorporated into and constitute a part of this application and, together with the written description, serve to explain the present invention. The appended drawings are briefly described as follows.

Medical devices such as guidewires are sufficiently slender to be inserted into a lumen such as an artery, a vein, a throat, an ear canal, a nasal passage, a urethra or any number of other lumens or bodily passages. These medical devices enable physicians to perform non-invasive surgery resulting in a substantially shortened recovery period as compared to conventional surgery by preventing the need to cut a substantial opening in a subject or a patient to provide local access for performing a surgical procedure or medical operation.

As used herein, the terms "subject" or "patient" refer to the recipient of a medical intervention with the device. In certain aspects, the patient is a human patient. In other aspects, the patient is a companion, sporting, domestic or livestock or other animal.

As used herein, the terms "ionic electroactive polymer actuator" refer to a component of a medical device comprising a thin polymer electrolyte member within which cations migrate in response to an electrical field imposed thereon, and one or more electrodes disposed on the surface of the polymer electrolyte member. As described herein, the "ionic electroactive polymer actuator" may be provided at the distal end in a bendable portion of a medical device to be responsible for moving or selectively bending the distal end thereof. More specifically, selective electrical energization of one or more electrodes causes the polymer electrolyte member or members to deform asymmetrically as a result of contraction along a side or portion of the polymer electrolyte member and/or swelling along a side or portion of the polymer electrolyte member. It will be understood that cations within the polymer electrolyte member will migrate towards an anodically energized electrode, and away from a cathodically energized electrode, while remaining within the matrix of the polymer electrolyte member. This causes a portion of the polymer electrolyte member adjacent to an anodically energized electrode to swell and a portion of the polymer electrolyte member adjacent to a cathodically energized electrode to contract, thereby causing the polymer electrolyte member to bend. Coordinated control of electrical signals delivered to the electrodes through electrically-conductive wires produces bending of the polymer electrolyte member in an intended or selected direction. In a relaxed or un-energized state, the polymer electrolyte member of the ionic electroactive polymer actuator remains in its original form.

As used herein, the term "polymer electrolyte member" refers to a layer, membrane, rod or component in any shape or form comprising a polymer host and an electrolyte solvent (e.g., water, an ionic liquid or the like). The polymer host comprises, for example, but not by way of limitation, fluoropolymers and intrinsically conducting polymers. For example, the polymer electrolyte member can comprise a porous polyvinylidene fluoride or polyvinylidene difluoride, a highly non-reactive thermoplastic fluoropolymer produced by the polymerization of vinylidene difluoride, and containing ionic liquid or salt water. Alternately, the polymer electrolyte can comprise a gel formed by polyvinylidene fluoride or polyvinylidene difluoride, propylene carbonate and an ionic liquid.

As used herein, the terms "electrically-conductive wire" or "electrically-conductive conduit" refer to a component that conducts electrical signals from a source of electricity to one or more of the plurality of electrodes to affect bending of the polymer electrolyte member, and may comprise a noble metal for superior chemical stability and corrosion resistance. For example, but not by way of limitation, the electrically-conductive wires or conduits that deliver potential to selected electrodes to actuate the polymer electrolyte member comprise highly conductive platinum, a platinum alloy, silver or a silver alloy, or they comprise gold or a gold alloy which, in addition to being chemically stable and corrosion resistant, is malleable and can be advantageously formed into very slender electrically-conductive wires with very low inherent resistance to bending.

The following paragraphs describe certain embodiments of medical devices useful to perform, or to enable the performance of, surgical operations using the same, and methods that can be used to enable the preparation of such medical devices for same. It will be understood that other embodiments of medical devices and methods are within the scope of the claims appended herein below, and the illustration of such embodiments is not limiting of the present invention. <FIG> illustrates one embodiment of a medical device, comprising an isometric view of a portion of a guidewire <NUM>. <FIG> is a perspective view of the portion of a guidewire <NUM> of <FIG> with the polymer sleeve removed to reveal details of the components therein. The guidewire <NUM> comprises an elongate, flexible portion <NUM> and a controllably bendable portion <NUM> disposed at the distal end <NUM> of the elongate, flexible portion <NUM>. The elongate and flexible portion <NUM> further comprises a core <NUM> (see e.g., <FIG>) and a sleeve <NUM> surrounding the core <NUM>. The bendable portion <NUM> includes an ionic electroactive polymer actuator <NUM> comprising a polymer electrolyte member <NUM> disposed adjacent to and generally collinear to the core <NUM> of the elongate, flexible portion <NUM> and centrally within a plurality of energizable electrodes <NUM> as they are positioned in <FIG> and <FIG>. Each of the plurality of electrodes <NUM> that substantially surround the exterior surface <NUM> of the polymer electrolyte member <NUM> is connected to a distal end <NUM> of a different one of a plurality of electrically-conductive wires <NUM>, through which an electrical signal or potential may be supplied to the so connected electrode <NUM>.

As shown in <FIG>, the elongate and flexible portion <NUM> is extendable from an operable portion of a medical device which is provided at the proximal end <NUM> of the elongate and flexible portion <NUM> and available for manipulation by the operator (not shown. The core <NUM> of the elongate, flexible portion <NUM> is sufficiently slender to be inserted into a lumen (not shown) of a body (not shown). Also, the core <NUM> is sufficiently flexible and substantially axially incompressible so that it can be advanced through a lumen having a winding or tortuous pathway by pushing or driving the elongate, flexible portion <NUM> forward after it is introduced into the lumen of the body (not shown). The core <NUM> can include any suitable material including metals, metal alloys, polymers, or the like, or combinations or mixtures thereof. Some examples of suitable metals and metal alloys include stainless steel, such as <NUM> v stainless steel; nickel-titanium alloy, such as nitinol, nickel-chromium alloy, nickel-chromium-iron alloy, cobalt alloy, or the like; or other suitable material. The term "nitinol" herein is referred to a metal alloy of nickel and titanium. The entire core <NUM> can be made of the same material (e.g. nitinol), or in some embodiments, can include portions or sections made of different materials. In some embodiments, the material used to construct core <NUM> is chosen to impart varying flexibility and stiffness characteristics to different portions of shaft <NUM>. For example, a proximal portion and a distal portion of core <NUM> may be formed of different materials (i.e., materials having different moduli of elasticity) resulting in a difference in flexibility of the core <NUM> at different locations thereof. In some embodiments, the material used to construct the proximal portion can be relatively stiff for pushability and torqueability (ability to twist without significant energy storage or hysteresis) of this portion of the core <NUM>, and the material used to construct the distal portion can be relatively flexible by comparison for better lateral trackability and steerability of the distal portion of the core <NUM>. For example, the proximal portion of the core <NUM> can be formed of straightened 304v stainless steel wire, and the distal portion of the core <NUM> can be formed of a straightened super elastic or linear elastic alloy (e.g., nitinol) wire. <FIG> illustrate various embodiments of the elongate, flexible portion <NUM>. In some embodiments, the core <NUM> has a solid cross-section (see <FIG> and <FIG>). In the solid core embodiment of <FIG>, the core <NUM> is a metallic core wire comprising a solid metallic material <NUM>. The core <NUM> having the solid metallic material <NUM> can couple to at least one of the electrodes <NUM> and serve as an additional electrically-conductive conduit to conduct electrical signals selectively sent from a source of electricity to one or more of the plurality of electrodes <NUM> to control bending of the polymer electrolyte member <NUM>, so that the number of electrically-conductive wires <NUM> attached on the exterior surface <NUM> of the core <NUM> can be reduced accordingly, e.g. being reduced to one electrically-conductive wire <NUM> as compared with the two electrically-conductive wires <NUM> of <FIG>. In some alternative embodiments, the core <NUM> may have a hollow cross-section. For example, as shown in <FIG>, an inner lumen <NUM> is formed within the core <NUM> along the elongate and flexible portion <NUM> for receiving the electrically-conductive wires <NUM>.

A polymer sleeve <NUM> surrounds the core <NUM> and a portion of the ionic electroactive polymer actuator <NUM> to facilitate guidewire maneuverability within a body lumen or passage. The polymer sleeve <NUM> comprises, for example, a polymer such as a thermoplastic or thermosetting polymer. For example, the polymer sleeve <NUM> may comprise polyether block amide(PEBA), polyurethane, polyether-ester, polyester, polyaryletherketone (PAEK) or linear low-density polyethylene, and the like, or copolymers or mixtures or combinations thereof. Additionally, the polymer sleeve <NUM> may comprise polymers such as polyamide, elastomeric polyamides, block polyamide/ethers, silicones, polyethylene, and the like, or mixtures, combinations, or copolymers thereof, or with any of the other materials listed above. In a preferred embodiment, the polymer sleeve <NUM> comprises PEBAX® (available from Arkema) or polytetrafluoroethylene (PTFE) or a combination thereof to provide relatively flexible polymeric properties for the sleeve <NUM>. Some other suitable exemplary materials for the polymer sleeve <NUM> include nylon, polyetheretherketone (PEEK), polyimide (PI), polyetherimide (PEI), fluorinated ethylene propylene (FEP) and/or perfluoroalkoxy polymer resin (PFA). By employing careful selection of materials and processing techniques, thermoplastic, solvent soluble, and thermosetting variants of these and other materials can be employed to achieve the desired results such as flexibility, kink resistance or the like.

Additionally, in some embodiments, a coating, for example a lubricious (e.g., hydrophilic) or other type of coating may be applied over portions or all of the polymer sleeve <NUM>, and/or other portions of the guidewire <NUM>. Hydrophobic coatings such as fluoropolymers provide a dry lubricity which improves guidewire handling and device exchanges. Lubricious coatings improve steerability within a body lumen or passage, and improve lesion crossing capability therein. Suitable lubricious polymers are well known in the art and may include hydrophilic polymers such as polyarylene oxides, polyvinylpyrolidones, polyvinylalcohols, hydroxy alkyl cellulosics, algins, saccharides, caprolactones, and the like, and mixtures and combinations thereof. In a preferred embodiment, the polymer sleeve <NUM> is coated with a hydrophilic polymer as discussed above.

The electrically-conductive wires <NUM> are connected to the core <NUM> using any suitable connecting technique (e.g. mechanical fasteners (bolts or clamps), laser welding, ultrasonic bonding, brazing and soldering). For example, in <FIG>, each of the electrically-conductive wires <NUM> is disposed linearly along the length of the exterior surface <NUM> of the core <NUM>. Alternatively, each of the plurality of electrically-conductive wires <NUM> is helically or interweavingly wrapped around the exterior surface <NUM> of the core <NUM> as shown in <FIG>. Then, each of the electrically-conductive wires <NUM> of <FIG> is secured with respect to the polymer sleeve <NUM>, the core <NUM> and at least a portion of the proximal end of the ionic electroactive polymer actuator <NUM>. (see, e.g. <FIG>). In other embodiments, the electrically-conductive wires <NUM> can pass through the inner lumen <NUM> of <FIG>. In yet another embodiment, a plurality of grooves <NUM> as shown in <FIG> are formed to extend linearly along the exterior surface <NUM> of the core <NUM>, each groove receiving one of the electrically-conductive wires <NUM> therein, respectively. The polymer sleeve <NUM> further covers the grooves <NUM> to enclose the electrically-conductive wires <NUM> therein.

<FIG> and <FIG> illustrate the elongate, flexible portion <NUM> and the bendable portion <NUM> of the guidewire <NUM> of <FIG> according to one embodiment where a tapered end <NUM> is provided adjacent to the distal end <NUM> of the core <NUM> of the elongate, flexible portion <NUM>. The diameter of the core <NUM> includes a minor diameter portion extending from a transition to the distal end thereof, a major diameter portion extending from the transition to the proximal end thereof (not shown), and the transition transitions the core <NUM> diameter between the major to minor diameter portions along one or more tapers or steps. In some embodiments, as shown in <FIG>, the core <NUM> surrounded by the polymer sleeve <NUM> has a tapered portion <NUM> having a geometry that decreases in cross sectional area as the surface of the core becomes closer to the distal end <NUM> of the elongate, and the reduced cross section of the minor diameter portion of the core <NUM> at the distal end <NUM> contacts a surface of the proximal end <NUM> of the ionic electroactive polymer actuator <NUM>. The polymer sleeve <NUM> is then formed by extruding any suitable polymer(s) as described above onto the core <NUM> and the proximal end <NUM> of the ionic electroactive polymer actuator <NUM> to firmly secure them together. Also, to be firmly interconnected, in other embodiments shown in <FIG>, the minor diameter portion extending from the tapered end <NUM> to the distal end <NUM> of the core is embedded in an opening provided therefor extending inwardly of the proximal end <NUM> of the polymer electrolyte member <NUM>. In some embodiments, if tapered, the core <NUM> can include a uniform or a nonuniform transition of the tapered portion <NUM>, depending on the transition characteristics desired. For example, the diameter transition surface profile of the tapered portion <NUM> of the core <NUM> may be linear, curvilinear, or step-wise, and can include more than one transition type or change in diameter. The angle of any such transition with respect to a centerline of the core can vary, depending upon the desired flexibility characteristics of the core <NUM>. The length of the tapered portion <NUM> may be selected to obtain a more (longer length) or less (shorter length) gradual transition in stiffness along its length in the core <NUM>. The tapered portion <NUM> of the core <NUM> may be tapered or shaped by any one of a number of different techniques known in the art, for example, by cylindrical grinding (e.g. outside diameter grinding or centerless grinding), but the tapering method is not limited to this.

<FIG> is an isometric view of an end portion of the bendable portion <NUM> of the embodiment of the guidewire <NUM> of <FIG> and <FIG>, illustrating the bendable portion <NUM> in the straight mode. The bendable portion <NUM> includes an ionic electroactive polymer actuator <NUM> comprising a rodlike polymer electrolyte member <NUM> disposed adjacent to the distal end <NUM> of elongate, flexible portion <NUM> <FIG> and centrally to an angularly-distributed plurality of energizable electrodes <NUM> on the circumference thereof, i.e., the exterior surface <NUM>. Each of the plurality of electrodes <NUM> that are laid out to surround the exterior surface <NUM> of the polymer electrolyte member <NUM> is connected to a distal end <NUM> of an electrically-conductive wire <NUM> through which an electrical signal or potential is selectively supplied to the connected electrode <NUM>, and spaced from one another by a gap formed of a portion of the exterior surface <NUM> of the polymer electrolyte member <NUM>. In one embodiment, the ionic electroactive polymer actuator <NUM> may comprise a plurality of angularly distributed electrodes <NUM> equi-angularly distributed about the exterior surface <NUM> of the polymer electrolyte member <NUM>. For example, but not by way of limitation, the ionic electroactive polymer actuator <NUM>, in the embodiment of <FIG>, comprises the polymer electrolyte member <NUM> and four angularly-distributed electrodes <NUM> that are separated or spaced apart along the exterior surface <NUM> of the polymer electrolyte member <NUM>, one from the others by about <NUM> degrees (<NUM> radians) between their centers or centerlines <NUM>. As another example, but not by way of limitation, the ionic electroactive polymer actuator <NUM> may comprise eight angularly-distributed electrodes <NUM> that are separated along the exterior surface <NUM> of the polymer electrolyte member <NUM>, between their centerlines, by about <NUM> degrees (<NUM> radians). In yet another example, the ionic electroactive polymer actuator <NUM> may comprise three angularly-distributed electrodes <NUM> that are separated along the exterior surface <NUM> of the polymer electrolyte member <NUM>, between their centerlines, one from the others by about <NUM> degrees (<NUM> radians). It will be understood that each of the plurality of electrodes <NUM> occupies a circumferential span along the surface of the polymer electrolyte member, and that the "angular separation" may therefore be stated in terms of the centerlines of the electrodes instead of in terms of the adjacent edges of the electrodes, which will be much closer to the adjacent edge of the adjacent electrode. In some embodiments of the medical device, the electrodes are spaced in a manner to provide a substantial gap as insulation channels intermediate adjacent electrodes.

In one embodiment, the ionic electroactive polymer actuator <NUM> of <FIG> is an ionic polymer-metal composite (IPMC) actuator. In one embodiment, the ionic electroactive polymer actuator <NUM> comprises a polymer electrolyte member <NUM> made of PVDF-HFP that is impregnated with EMITF (as an electrolyte). Alternately, other embodiments of the ionic electroactive polymer actuator <NUM> of the guidewire <NUM> may include a polymer electrolyte member <NUM> that comprises a perfluorinated ionomer such as Aciplex™ (available from Asahi Kasei Chemical Corp. of Tokyo, Japan), Flemion® (available from AGC Chemical Americas, Inc. of Exton, Pennsylvania, USA), fumapem® F-series (available from Fumatech BWT GmbH, Bietigheim-Bissingen, Federal Republic of Germany) or Nation® (available from The Chemours Company of Wilmington, Delaware, USA.

In one embodiment, the electrodes <NUM> may comprise one of platinum, gold, carbon-based material, or a combination (e.g. a composite) thereof. The carbon-material may comprise, for example but not limited to, carbide-derived carbon (CDC), carbon nanotube (CNT), graphene, a composite of carbide-derived carbon and the polymer electrolyte member <NUM>, and a composite of carbon nanotube and the polymer electrolyte member <NUM>. In an exemplary embodiment, the electrodes <NUM> are double-layered, comprising: a layer comprising a composite of carbon (CDC and/or CNT) and PVDF-HFP/EMITF and a gold layer. The electrodes <NUM> are integrated on the exterior surface <NUM> of the polymer electrolyte member <NUM> using any suitable techniques. For example, but not by way of limitation, metal electrodes <NUM> can be deposited (e.g. platinum or gold electrodes) thereon using an electrochemical process. Alternatively, the double-layered electrodes <NUM> can be prepared and integrated on the exterior surface <NUM> by the following steps: spraying a carbon-based material layer on the exterior surface <NUM>, spray coating a gold layer on the carbon-based material layer, followed by integrating the carbon-based material layer and a gold layer using a reflow process. The detail of the reflow process is discussed in PCT Application No. <CIT>; The bendable portion <NUM> is capable of being selectively and controllably deformed into a bent mode by selective energization of one or more of the plurality of electrodes <NUM>, as will be explained in further detail below. <FIG> is a an isometric view of a portion of the bendable portion <NUM> of <FIG> in the deformed or bending mode. Each of the plurality of electrodes <NUM> is connected to a distal end <NUM> of an electrically-conductive wire <NUM> (<FIG>) through which an electrical signal may be applied to the electrode <NUM> to which the wire <NUM> is connected, thereby causing metal cations within the polymer electrolyte member <NUM> to move in a direction determined by the presence of a cathodic or anodic electrical potential selectively applied to individual ones of the electrodes <NUM>. This cation migration produced by the applied electrical potential causes the polymer electrolyte member <NUM> to swell in the portion of the polymer electrolyte member <NUM> disposed proximal to an electrode supplied with the anodic potential and resultantly bend or warp in the direction of the remaining unswelled portion of the polymer electrolyte member <NUM>. As a result, the magnitude and the direction of the bending deformation of the polymer electrolyte member <NUM> of the ionic electroactive polymer actuator <NUM> can be controlled by strategically selecting which of the electrodes <NUM> to energize and by adjusting the magnitude and sign (+ or -) of the electrical potential applied through the electrically-conductive wire <NUM> to the electrodes <NUM>.

Alternately, in the event that the bendable portion <NUM> is observed to be in a deformed (bent) mode in the absence of the application of one or more electrical potentials to one or more of the plurality of the electrodes <NUM>, the magnitude of the observed deflection can be determined by sensing the different electrical potentials imposed on different ones of the wires as a result of the bending, and equate those potential(s) to the extent of bending of the bendable portion <NUM> from a free state to a bent state by imposing the potentials electrically form a voltage source, to determine the magnitude and direction of an external force being applied to the bendable portion <NUM> or, alternately, in the event that the application of a known potential on the electrodes <NUM> fails to produce an anticipated deformation of the bendable portion <NUM>, the difference between the anticipated deformation and the actual deformation (if any) can be used as an indicator of the magnitude of an external force applied to the bendable portion <NUM> of the guidewire <NUM>.

<FIG> is a cross-sectional view of the bendable portion <NUM> of <FIG> illustrating one embodiment wherein a first selected set of four electrical potentials are applied to four circumferentially distributed electrodes <NUM> disposed about the exterior surface <NUM> of the polymer electrolyte member <NUM> to provide two degrees of bending freedom (e.g. bending along X-axis direction and/or Y-axis direction). <FIG> illustrates the charge (sign) of the electrical potential applied to the plurality of angularly distributed electrodes <NUM> to impart bending of the bendable portion <NUM> in the direction of the arrow <NUM>. It will be understood that the application of a positive potential on the electrodes <NUM> on the left and right sides of the bendable portion <NUM> of <FIG>, in addition application of a positive potential to the electrode <NUM> at the top of <FIG>, and further in addition to the application of a negative potential to the electrode <NUM> at the bottom of <FIG>, will result in a different amount of deformation than would occur as a result of the application of only a positive potential on the electrode <NUM> at the top of <FIG> and a negative potential imparted to the remaining electrodes <NUM>. It will be understood that the user may select the plurality of electrical signals that produces the deformation desired by the user.

<FIG> is a cross-sectional view of the bendable portion <NUM> of <FIG> revealing another embodiment wherein a second selected set of four electrical potentials are applied to the circumferentially distributed electrodes <NUM> disposed about the polymer electrolyte member <NUM>. <FIG> illustrates the application of a positive potential to the electrode <NUM> at the top of the bendable portion <NUM> of <FIG> and also to the electrode <NUM> at the right side of the bendable portion <NUM> of <FIG> further illustrates the application of a negative potential to the electrode <NUM> at the bottom of <FIG> and also to the electrode <NUM> at the left side of <FIG>. The deformation of the polymer electrolyte member <NUM> which results from the application of these electrical potentials is in the direction of the arrow <NUM>.

It will be understood from <FIG> that the bendable portion <NUM> of the guidewire <NUM> can be bent in multiple directions and with varying degrees of deformation or deflection by strategic control of the electrical charges imparted to each of the individual electrodes <NUM>. Although the embodiment illustrated in <FIG> illustrates a bendable portion <NUM> including four electrodes <NUM>, it will be understood that the bendable portion <NUM> of the actuation part <NUM> of the guidewire <NUM> may include fewer than four or more than four electrodes <NUM>, and such other embodiments will have differing deflection and deformation directional capacities and thus provide more or less degree(s) of freedom.

<FIG> is an isometric view of the bendable portion <NUM> of the guidewire <NUM> according to another embodiment illustrating an ionic electroactive polymer actuator 110a where two circumferentially distributed electrodes are respectively disposed about the exterior surface 113a of the rodlike polymer electrolyte member 111a to provide one degree of freedom in bending motion (e.g. up or down. A top electrode 112a is disposed about the top of the exterior surface <NUM> of the rodlike polymer electrolyte member 111a and a bottom electrode 112a' is disposed symmetrically about the bottom of the exterior surface 113a. As described above, for example, the top portion of the polymer electrolyte member 111a adjacent to the energized top electrode 112a will contract (given the application of a positive potential to the top electrode 112a of <FIG>), while the bottom portion of the polymer electrolyte member 111a adjacent to the energized bottom electrode 112a' will swell (given the application of a negative potential to the bottom electrode 112a'), thereby causing the polymer electrolyte member 111a to bend in the direction of the arrow <NUM>.

<FIG> illustrates another embodiment of a medical device, comprising an isometric view of a portion of a guidewire <NUM>. <FIG> is an isometric view of the guidewire of <FIG> with an overlying polymer sleeve shown in phantom in <FIG> to reveal details of the components therein. The details related to the elongate, flexible portion <NUM> and the components thereof can be understood by reference to the above paragraphs. Compared with the above-described embodiments, the ionic electroactive polymer actuator 110b of the guidewire <NUM> of <FIG> and <FIG> is provided herein in a different cross-sectional shape. For example, but not by way of limitation, in one embodiment, <FIG> is an isometric view of the bendable portion <NUM> of the guidewire <NUM> of <FIG> and <FIG> illustrating a rectangular in cross section, or more specifically a "sandwich-structured" ionic electroactive polymer actuator 110b with two circumferentially distributed electrodes -a top electrode 112b and a bottom electrode 112b' which are respectively disposed about the top and the bottom exterior surface 113b of the rectangular in section polymer electrolyte member 111b to form a "sandwich" structure. The "sandwich-structured" ionic electroactive polymer actuator 110b can be prepared by any suitable techniques. For example, but not by way of limitation, the electrodes 112b, 112b' can be fabricated by casting thereof and then be assembled with the rectangular polymer electrolyte member 111b using heat-pressing without additional precise micromachining, thereby no gaps, which would form insulation channels, remaining between adjacent electrodes and the concomitant open circuit issues which may result from such processing. Similarly, the ionic electroactive polymer actuator 110b can bend as described in <FIG> to provide one degree of freedom in bending motion (e.g. up or down in Y-axis direction) when the top electrode 112b and the bottom electrode 112b' are energized with an electric potential of opposite sign or potential, i.e., + and-.

The electrically-conductive wires <NUM> are interconnected with the electrodes <NUM> using any suitable connecting techniques. For example, in the embodiment of <FIG>, the electrically-conductive wires <NUM> are interconnected with at least a portion of each of the electrodes <NUM> (e.g. being integrated and embedded) at the proximal end <NUM> of the ionic electroactive polymer actuator <NUM> using conducting paste or laser welding. Then, the polymer sleeve <NUM> is overlayed on the core <NUM>, a portion of the proximal end <NUM> and the electrically-conductive wires <NUM> connected thereto, to firmly secure them together.

<FIG> illustrates a side sectional view of the elongate, flexible portion <NUM> and the bendable portion <NUM> of the guidewire according to another embodiment. Here, a conductive bridge <NUM> is formed over the surface of the proximal end <NUM> of the ionic electroactive polymer actuator <NUM> to interface with the electrodes <NUM> and the polymer electrolyte member <NUM> and facilitate transmission of electrical signals therebetween. The electrically-conductive wire <NUM> is interconnected to the exterior surface <NUM> of the core <NUM> from the proximal end <NUM> (see, e.g. <FIG>) to the distal end <NUM> and a portion of the tapered end <NUM> of the elongate, flexible portion <NUM>. The reduced diameter portion of the core <NUM> extending from the tapered portion to the distal end <NUM> thereof, and thus the distal end <NUM> of the electrically-conductive wire <NUM>, is embedded into an opening provided in the polymer electrolyte member <NUM> and where the conductive bridge <NUM> extends inwardly of the opening into which the reduced diameter extends, a greater area of contact between the conductive bridge <NUM> and the wire <NUM> can be achieved. The tip of the distal end <NUM> of the reduced diameter portion may be spaced from the terminal end of the opening in the polymer electrolyte member as shown in <FIG>, or may be grounded thereagainst. The conductive bridge <NUM> can be prepared by applying any conductive foil or tape made of metallic materials (e.g. gold, silver or copper) or non-metallic materials comprising conductive polymers onto the surface of the electrodes <NUM> and the polymer electrolyte member <NUM> using any suitable techniques (e.g. using adhesives, coating, plating, etching or depositing, but not limited to this). Then, as shown in <FIG>, the polymer sleeve <NUM> (shown in phantom) overlaying the core <NUM> and a portion of the proximal end <NUM> of the ionic electroactive polymer actuator <NUM> and the electrically-conductive wires <NUM> connected thereto, firmly secures them together.

<FIG> illustrates a sectional side view of the elongate, flexible portion <NUM> and the bendable portion <NUM> of the guidewire <NUM> having generally the same configuration as that shown in, and described herein with respect to, <FIG> according to one embodiment. <FIG> illustrates a sectional side view of the bendable portion <NUM> of <FIG>. An inner lumen <NUM> is formed within the core <NUM> over the length of the elongate and flexible portion <NUM> and a corresponding lumen extends into a portion of the polymer electrolyte member <NUM> at the proximal end <NUM> thereof. In <FIG>, individual conductive bridges 13a are shown provided at the distal end <NUM> of ionic electroactive polymer actuator <NUM> to electrically connect together the electrodes <NUM> and the polymer electrolyte member <NUM>, with the electrically-conductive wires <NUM> passing through the inner lumen <NUM> and embedded into the polymer electrolyte member <NUM> from the proximal end <NUM> to the distal end <NUM> thereof, thereby electrically connecting to the conductive bridges 13a using conventional wire bonding techniques such as soldering, crimping, stapling, pinching, welding, conductive adhesive (e.g., using conductive epoxy), and the like.

Referring back to <FIG> and <FIG>, the "sandwich-structured" ionic electroactive polymer actuator 110b can be prepared by the following exemplary method. The polymer electrolyte member 111b is fabricated by first dissolving a fluoropolymer resin (e.g. poly(vinylidene fluoride-co-hexafluoropropylene (P(VDF-HFP)) in appropriate solvent such as acetone, dimethylacetamide (DMAc) or the like. The obtained PVDF-HFP formulation is then cast on a Polytetrafluoroethylene (PTFE) substrate using a Doctor blade method and cured at room temperature. Additionally, the PVDF-HFP film is dried under vacuum at <NUM> C to remove solvent residues. Finally, the PVDF-HFP film is heat-pressed between two PTFE plates and annealed at <NUM>-<NUM> C for <NUM> hours. After cooling down to room temperature, the PVDF-HFP film is peeled off from the PTFE substrate. The final film thickness is around <NUM>-<NUM>. Next, the polymer film is impregnated with appropriate ionic liquid electrolyte, such as <NUM>-Ethyl-<NUM>-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIMTFSI) or <NUM>-Ethyl-<NUM>-methylimidazolium trifluoromethanesulfonate (EMITF) at <NUM>-<NUM> C for at least <NUM> hours.

Then, the top electrode 112b and the bottom electrode 112b' are respectively disposed about the top and the bottom exterior surface 113b of the obtained polymer electrolyte member 111b according to the following exemplary embodiment. Carbon-polymer composite used for the layered top electrode 112b and bottom electrode 112b' is fabricated by preparing a dispersion containing a desired conductive carbon material, PVDF-HFP and ionic liquid in a solvent (e.g. dimethylacetamide (DMAc)). Conductive carbon material used herein may be carbide-derived carbon (CDC), carbon nanotubes, carbon aerogel, graphene or other carbon allotrope or the combination thereof. The carbon-polymer mixture is stirred at elevated temperature for <NUM> hours to achieve homogenous dispersion. Then, the dispersion is treated with ultrasonic bath and ultrasonic probe for <NUM> hours. Thereafter, the obtained carbon dispersion is cast on a PTFE substrate using a Doctor's blade method and dried at room temperature for at least <NUM> hours. After that, the film is dried under vacuum at <NUM> C for <NUM> hours. Finally, the carbon-polymer composite film is heat-pressed at <NUM> - <NUM> C for <NUM>-<NUM>.

The electrical conductivity of the obtained carbon-polymer composite film is often inadequate to provide proper electromechanical performance for the ionic electroactive polymer actuator 110b due to the type of carbon material used. Thus, in some embodiments, a thin gold foil with a thickness of <NUM>-<NUM> may be coated over the obtained carbon-polymer composite film to serve as a conductive current collector and increase the electrical conductivity of the electrode. Alternatively, in other embodiments, the carbon-polymer composite film may be covered with a gold nanoparticle dispersion coating using a spray-coating process to form the top electrode 112b and the bottom electrode 112b'.

Finally, the obtained polymer electrolyte member 111b, the top electrode 112b and the bottom electrode 112b' are assembled using heat-pressing at <NUM>-<NUM> C for <NUM>-<NUM>, depending on the type of carbon material and electrode configuration used, to form the "sandwich-structured", laminated ionic electroactive polymer actuator 110b. In some embodiments, the total thickness of the ionic electroactive polymer actuator 110b is around <NUM>-<NUM>. To be used in the bendable portion <NUM> of the guidewire <NUM>, in one embodiment, the obtained ionic electroactive polymer actuator 110b may be cut into a <NUM> wide strip with a length of <NUM>.

A process for manufacturing a guidewire shown in <FIG> and <FIG> is illustrated as shown in <FIG>. <FIG> illustrate schematically the integration of the ionic electroactive polymer actuator 110b and the reduced width portion of the core <NUM> distal to the tapered portion <NUM> at the distal end <NUM> of the core <NUM> of the elongate, flexible portion <NUM>. <FIG> is an exploded view showing a core <NUM> and an ionic electroactive polymer actuator <NUM> of the guidewire shown in <FIG> and <FIG>. <FIG> is an isometric view of the core <NUM> and ionic electroactive polymer actuator <NUM> of the guidewire shown in <FIG> and <FIG> assembled on the core <NUM>. <FIG> is a perspective view of <FIG> with a section of the ionic electroactive polymer actuator <NUM> shown in phantom to better reveal details of the components therein. As shown in <FIG>, a top electrode 112b and a bottom electrode 112b' are respectively disposed about the top and the bottom exterior surfaces 113b of the rectangular polymer electrolyte member 111b, at a rectangular in section reduced width portion of the core extending distally of the tapered portion <NUM> of the core <NUM>. In <FIG>, the reduced width portion and a portion of the tapered portion <NUM> of the core are then sandwiched between two rectangular polymer electrolyte member 111b using any suitable technique (e.g. heat pressing, reflowing or the like) to form a laminated "sandwich" structure.

<FIG> schematically illustrate the connection of the electrically-conductive wires <NUM> to the electrodes 112b, 112b' of the ionic electroactive polymer actuator 110b and the core <NUM> of the elongate, flexible portion <NUM>. <FIG> is perspective view of a core, an ionic electroactive polymer actuator and the electrically-conductive wires of a guidewire according to one embodiment. <FIG> is a side view of <FIG>. <FIG> is a perspective view of <FIG> with the ionic electroactive polymer actuator shown in phantom to better reveal details of the components therein. <FIG> is a side view of <FIG> with the ionic electroactive polymer actuator shown in phantom to better reveal details of the components therein. Here, the electrically-conductive wires <NUM> shown in <FIG> are wound over the core <NUM> from the proximal end <NUM> to the distal end <NUM> thereof, and then the distal end <NUM> of each of the electrically-conductive wires <NUM> is interconnected to a surface of a single one of the electrodes 112b, 112b' using any suitable connecting technique (e.g. conducting paste or laser welding. In some embodiments, the reduced diameter portion of the core <NUM> distal of the tapered portion <NUM> is further embedded into the distal end <NUM> of ionic electroactive polymer actuator 110b to be better secured thereto, as shown in <FIG>.

<FIG> illustrate schematically the integration of the polymer sleeve <NUM> over the core <NUM>, the proximal end 114b of the ionic electroactive polymer actuator 110b and the electrically-conductive wires <NUM>. <FIG> is an isometric view of an elongate, flexible portion <NUM> and a bendable portion <NUM> of a guidewire according to one embodiment, wherein the elongate, flexible portion <NUM> comprises a core <NUM> (see e.g., <FIG>) and a polymer sleeve <NUM> surrounding the core <NUM> while the bendable portion 11b includes an ionic electroactive polymer actuator 110b as described above (see. e.g. <FIG>). <FIG> is a side view of <FIG>. <FIG> is an isometric view of <FIG> with a section of a polymer sleeve shown in phantom to better reveal details of the components therein. <FIG> is a side view of <FIG> with a section of a polymer sleeve indicated in solid lines to better reveal details of the components therein. <FIG> is a side view of <FIG> with a section of a polymer sleeve and an ionic electroactive polymer actuator shown in phantom to better reveal details of the components therein. As shown in <FIG>, a polymer sleeve <NUM> is further provided to surround the core <NUM>, a portion (i.e. the proximal end <NUM>) of the ionic electroactive polymer actuator 110b and the electrically-conductive wires <NUM> thereon to facilitate guidewire maneuverability. The polymer sleeve <NUM> may be formed by extruding any suitable polymers as described herein onto the core <NUM> and the proximal end 114b of the ionic electroactive polymer actuator 110b to firmly secure them together. Then, a parylene coating (not shown) can be further applied to the outer surface of the resulting integrated guidewire <NUM> to provide the final moisture and dielectric barrier protection. The parylene coating also helps to provide biocompatibility and excellent lubricity over the entire length of the guidewire <NUM>.

Claim 1:
A medical device, comprising:
a bendable portion (<NUM>) having at least one ionic electroactive polymer actuator, the actuator (<NUM>) comprising:
at least one polymer electrolyte member (<NUM>) defining at least a surface, the at least one polymer electrolyte member including a polymer electrolyte member proximal end and a polymer electrolyte member distal end that is distal to the polymer electrolyte member proximal end; and
a plurality of electrodes (<NUM>) disposed about the at least a surface of the at least one polymer electrolyte member;
an elongate, flexible portion (<NUM>) defining a flexible portion proximal end and a flexible portion distal end, the flexible portion distal end contacting the polymer electrolyte member proximal end, the elongate, flexible portion further comprising:
a core (<NUM>) extending from the flexible portion proximal end to the flexible portion distal end and having a tapered portion that is adjacent to the flexible portion distal end and extends inwardly to the polymer electrolyte member proximal end, and
a sleeve (<NUM>) surrounding the core, and;
a plurality of electrically-conductive wires (<NUM>), each having a proximal end and a distal end coupled to at least one of the plurality of electrodes;
wherein, when an electrical signal supplied through at least one of the plurality of electrically-conductive wires to at least one of the plurality of electrodes, the at least one polymer electrolyte member bendably deforms in response to the electrical signal supplied through at least one of the plurality of electrically-conductive wires.