Capacitive intravascular pressure-sensing devices and associated systems and methods

Intravascular devices, systems, and methods are disclosed. In some embodiments, the intravascular devices are guide wires that include a capacitive pressure-sensing component disposed at a distal portion of the guide wire. Methods of making such intravascular devices, including various manufacturing and assembling techniques, are disclosed. Systems associated with such intravascular devices and methods of using such devices and systems are also disclosed.

TECHNICAL FIELD

The present disclosure relates to intravascular devices, systems, and methods. In some embodiments, the intravascular devices are guide wires that include a capacitive pressure-sensing component.

BACKGROUND

Heart disease is very serious and often requires emergency operations to save lives. A main cause of heart disease is the accumulation of plaque inside the blood vessels, which eventually occludes the blood vessels. Common treatment options available to open up the occluded vessel include balloon angioplasty, rotational atherectomy, and intravascular stents. Traditionally, surgeons have relied on X-ray fluoroscopic images that are planar images showing the external shape of the silhouette of the lumen of blood vessels to guide treatment. Unfortunately, with X-ray fluoroscopic images, there is a great deal of uncertainty about the exact extent and orientation of the stenosis responsible for the occlusion, making it difficult to find the exact location of the stenosis. In addition, though it is known that restenosis can occur at the same place, it is difficult to check the condition inside the vessels after surgery with X-ray.

A currently accepted technique for assessing the severity of a stenosis in a blood vessel, including ischemia causing lesions, is fractional flow reserve (FFR). FFR is a calculation of the ratio of a distal pressure measurement (taken on the distal side of the stenosis) relative to a proximal pressure measurement (taken on the proximal side of the stenosis). FFR provides an index of stenosis severity that allows determination as to whether the blockage limits blood flow within the vessel to an extent that treatment is required. The normal value of FFR in a healthy vessel is 1.00, while values less than about 0.80 are generally deemed significant and require treatment.

Often intravascular catheters and guide wires are utilized to measure the pressure within the blood vessel, visualize the inner lumen of the blood vessel, and/or otherwise obtain data related to the blood vessel. To date, guide wires containing pressure sensors, imaging elements, and/or other electronic, optical, or electro-optical components have suffered from reduced performance characteristics compared to standard guide wires that do not contain such components. For example, the handling performance of previous guide wires containing electronic components have been hampered, in some instances, by the need to physically couple the proximal end of the device to a communication line in order to obtain data from the guide wire, the limited space available for the core wire after accounting for the space needed for the conductors or communication lines of the electronic component(s), the stiffness and size of the rigid housing containing the electronic component(s), and/or other limitations associated with providing the functionality of the electronic components in the limited space available within a guide wire.

Accordingly, there remains a need for improved intravascular devices, systems, and methods that include pressure-sensing components.

SUMMARY

Embodiments of the present disclosure are directed to intravascular devices, systems, and methods.

In one embodiment, a guide wire is provided. The guide wire comprises a first elongate flexible element having a proximal portion and a distal portion, the first elongate flexible element being formed of a conductive material; a second elongate flexible element positioned around the first elongate flexible element, the second elongate flexible element being formed of a conductive material and having an outer diameter of 0.018″, 0.014″, or less; a radial capacitive pressure sensing structure coupled to the distal portion of the first elongate flexible element, the radial capacitive pressure sensing structure having a flexible membrane positioned around at least a portion of a cavity and a conductive member positioned around at least a portion of the flexible membrane such that the conductive member is displaced by changes in ambient pressure relative to a pressure in the cavity; and an application-specific integrated circuit (ASIC) coupled to the distal portion of the elongate flexible element, the ASIC in electrical communication with the conductive member of the radial capacitive pressure sensing component and the first and second flexible elongate elements.

In some instances, a section of the proximal portion of the first elongate flexible element is electrically coupled to a first conductive band. Further, in some instances a section of a proximal portion of the second elongate flexible element defines a second conductive band, such that the first conductive band is positioned proximal of the second conductive band. In some embodiments, the guide wire further includes an insulating member positioned between the first and second conductive bands, the insulating member being positioned around the first elongate flexible element. In some implementations, a majority of the second elongate flexible element is electrically isolated from the first elongate flexible element by a non-conductive layer covering the first elongate flexible element. The cavity of the radial capacitive pressure sensing structure includes a lumen of housing in some instances. In some embodiments, the housing includes a plurality of openings in a sidewall of the housing that are in communication with the lumen. In some instances, the plurality of openings are formed radially around a circumference of the housing where the housing has a cylindrical profile.

In another embodiment, an intravascular pressure-sensing system is provided. The system comprises a pressure-sensing guide wire having features similar to those described above; a processing system configured to process the data obtained by the pressure-sensing guide wire; and an interface configured to communicatively couple the pressure-sensing guide wire to the processing system.

In another embodiment, method of making a pressure-sensing apparatus is provided. The method includes: providing a first conductive tubular member, the first conductive tubular member having a lumen extending along its length; forming a plurality of openings through a sidewall of the first conductive tubular member, the plurality of openings in communication with the lumen of the first conductive tubular member; filling a portion of the lumen of the first conductive tubular member and the plurality of openings with a temporary material; forming a band of the temporary material around an outer surface of the first conductive tubular member, the band of the temporary material formed over the plurality of openings; forming a layer of flexible material over the first conductive tubular member such that the layer of flexible material covers the band of the temporary material; removing the temporary material filling the portion of the lumen and the plurality of openings; and removing the band of temporary material such that a space is created between an inner surface of the layer of flexible material and the outer surface of the first conductive member adjacent each of the plurality of openings such that the layer of flexible material is responsive to changes in ambient pressure relative to a pressure in the lumen of the first conductive tubular member.

DETAILED DESCRIPTION

As used herein, “flexible elongate member” or “elongate flexible member” includes at least any thin, long, flexible structure that can be inserted into the vasculature of a patient. While the illustrated embodiments of the “flexible elongate members” of the present disclosure have a cylindrical profile with a circular cross-sectional profile that defines an outer diameter of the flexible elongate member, in other instances all or a portion of the flexible elongate members may have other geometric cross-sectional profiles (e.g., oval, rectangular, square, elliptical, etc.) or non-geometric cross-sectional profiles. Flexible elongate members include, for example, guide wires and catheters. In that regard, catheters may or may not include a lumen extending along its length for receiving and/or guiding other instruments. If the catheter includes a lumen, the lumen may be centered or offset with respect to the cross-sectional profile of the device.

In most embodiments, the flexible elongate members of the present disclosure include one or more electronic, optical, or electro-optical components. For example, without limitation, a flexible elongate member may include one or more of the following types of components: a pressure sensor, a temperature sensor, an imaging element, an optical fiber, an ultrasound transducer, a reflector, a mirror, a prism, an ablation element, an RF electrode, a conductor, and/or combinations thereof. Generally, these components are configured to obtain data related to a vessel or other portion of the anatomy in which the flexible elongate member is disposed. Often the components are also configured to communicate the data to an external device for processing and/or display. In some aspects, embodiments of the present disclosure include imaging devices for imaging within the lumen of a vessel, including both medical and non-medical applications. However, some embodiments of the present disclosure are particularly suited for use in the context of human vasculature. Imaging of the intravascular space, particularly the interior walls of human vasculature can be accomplished by a number of different techniques, including ultrasound (often referred to as intravascular ultrasound (“IVUS”) and intracardiac echocardiography (“ICE”)) and optical coherence tomography (“OCT”). In other instances, infrared, thermal, or other imaging modalities are utilized.

The electronic, optical, and/or electro-optical components of the present disclosure are often disposed within a distal portion of the flexible elongate member. As used herein, “distal portion” of the flexible elongate member includes any portion of the flexible elongate member from the mid-point to the distal tip. As flexible elongate members can be solid, some embodiments of the present disclosure will include a housing portion at the distal portion for receiving the electronic components. Such housing portions can be tubular structures attached to the distal portion of the elongate member. Some flexible elongate members are tubular and have one or more lumens in which the electronic components can be positioned within the distal portion.

The electronic, optical, and/or electro-optical components and the associated communication lines are sized and shaped to allow for the diameter of the flexible elongate member to be very small. For example, the outside diameter of the elongate member, such as a guide wire or catheter, containing one or more electronic, optical, and/or electro-optical components as described herein are between about 0.0007″ (0.0178 mm) and about 0.118″ (3.0 mm), with some particular embodiments having outer diameters of approximately 0.014″ (0.3556 mm) and approximately 0.018″ (0.4572 mm)). As such, the flexible elongate members incorporating the electronic, optical, and/or electro-optical component(s) of the present application are suitable for use in a wide variety of lumens within a human patient besides those that are part or immediately surround the heart, including veins and arteries of the extremities, renal arteries, blood vessels in and around the brain, and other lumens.

“Connected”, “coupled”, and variations thereof as used herein includes direct connections, such as being glued or otherwise fastened directly to, on, within, etc. another element, as well as indirect connections where one or more elements are disposed between the connected elements.

“Secured” and variations thereof as used herein includes methods by which an element is directly secured to another element, such as being glued or otherwise fastened directly to, on, within, etc. another element, as well as indirect techniques of securing two elements together where one or more elements are disposed between the secured elements.

Referring now toFIG. 1, shown therein is a portion of an intravascular device100according to an embodiment of the present disclosure. In that regard, the intravascular device100includes a flexible elongate member102, a distal portion104adjacent a distal end105, and a proximal portion106adjacent a proximal end107. A component108is defined within the distal portion104of the flexible elongate member102proximal of the distal tip105. Generally, the component108is representative of one or more electronic, optical, or electro-optical components. In that regard, the component108may be a pressure sensor, a temperature sensor, an imaging element, an optical fiber, an ultrasound transducer, a reflector, a mirror, a prism, an ablation element, an RF electrode, a conductor, and/or combinations thereof. The specific type of component or combination of components can be selected based on an intended use of the intravascular device. As described below, in some particular embodiments of the present disclosure, the component108is a capacitive pressure sensor and associated components. In some instances, the component108is positioned less than 10 cm, less than 5, or less than 3 cm from the distal tip105.

In the illustrated embodiment, the component108is positioned between a proximal flexible element109and a distal flexible element110. The proximal flexible elements109,110typically have an increased flexibility relative to the flexible elongate member102. To that end, in some embodiments one or both of the flexible elements is a coil, a polymer tubing, a polymer tubing embedded with a coil, and/or combinations thereof. In that regard, the coils may take on any suitable form including round wire, flat wire, round and flat wire, constant gauge wire, variable gauge wire, constant pitch, variable pitch, single coil, multiple coils, overlapping coils, threading coils, and/or combinations thereof. In some instances, the component108is positioned within a housing. In that regard, the housing is a separate component secured to the proximal and distal flexible element109,110in some instances. In other instances, the housing is integrally formed as a part of at least one of the flexible elements109,110. To that end, in some instances the proximal and distal flexible element109,110are formed of a single, continuous flexible element with the component108secured thereto.

The intravascular device100also includes a connector111adjacent the proximal portion106of the device. In the illustrated embodiment, the proximal-most portion of the connector111is extends to the proximal end107of the intravascular device100. In other instances, the proximal-most portion of the connector111is spaced from the proximal end107of the flexible elongate member102. Generally, the spacing of the connector from the proximal end107is between 0% and 50% of the total length of the intravascular device100. While the total length of the intravascular device can be any length, in some embodiments the total length is between about 1300 mm and about 4000 mm, with some specific embodiments have a length of 1400 mm, 1900 mm, and 3000 mm. Accordingly, in some instances the connector111is spaced from the proximal end107between about 0 mm and about 1400 mm. In some specific embodiments, the connector111is spaced from the proximal end by a distance of 0 mm, 300 mm, and 1400 mm.

The connector111is configured to facilitate communication between the intravascular device100and another device. More specifically, in some embodiments the connector111is configured to facilitate communication of data obtained by the component108to another device, such as a computing device or processor. Accordingly, in some embodiments the connector111is an electrical connector. In such instances, the connector111provides an electrical connection to one or more electrical conductors that extend along the length of the flexible elongate member102and are electrically coupled to the component108. In other embodiments, the connector111is an optical connector. In such instances, the connector111provides an optical connection to one or more optical communication pathways (e.g., fiber optic cable) that extend along the length of the flexible elongate member102and are optically coupled to the component108. Further, in some embodiments the connector111provides both electrical and optical connections to both electrical conductor(s) and optical communication pathway(s) coupled to the component108. In that regard, it should again be noted that component108is comprised of a plurality of elements in some instances. In some instances, the connector111is configured to provide a physical connection to another device, either directly or indirectly. In other instances, the connector111is configured to facilitate wireless communication between the intravascular device100and another device. Generally, any current or future developed wireless protocol(s) may be utilized. In yet other instances, the connector111facilitates both physical and wireless connection to another device.

As noted above, in some instances the connector111provides a connection between the component108of the intravascular device100and an external device. Accordingly, in some embodiments one or more electrical conductors, one or more optical pathways, and/or combinations thereof extend along the length of the flexible elongate member102between the connector111and the component108to facilitate communication between the connector111and the component108. Generally, any number of electrical conductors, optical pathways, and/or combinations thereof can extend along the length of the flexible elongate member102between the connector111and the component108. In some instances, between one and ten electrical conductors and/or optical pathways extend along the length of the flexible elongate member102between the connector111and the component108. For the sake of clarity and simplicity, the embodiments of the present disclosure described below and shown inFIG. 1, include two electrically conductive bands112,114that are each coupled to an electrically conductive element extending the length of the flexible elongate member102to component108. In that regard, two electrically conductive bands112,114and associated conductive elements is particularly suited for use with the capacitive pressure sensing system of the present disclosure. However, it is understood that the total number of communication pathways and/or the number of electrical conductors and/or optical pathways is different in other embodiments. More specifically, the number of communication pathways and the number of electrical conductors and optical pathways extending along the length of the flexible elongate member102is determined by the desired functionality of the component108and the corresponding elements that define component108to provide such functionality.

Referring now toFIGS. 2-27, shown therein are various steps and/or aspects of manufacturing and/or assembling the intravascular device ofFIG. 1according to embodiments of the present disclosure. In that regard, theFIGS. 2-27will be described in the context of steps associated with manufacturing and/or assembling the intravascular device. It is understood that the described steps are exemplary in nature and that one or more of the steps may be omitted, one or more additional steps may be added, and/or the order of the steps may be changed without departing from the scope of the present disclosure. Further, one skilled in the art will recognize that there are alternative ways or manners of achieving the same results as the steps described below and that such alternative techniques are included within the scope of the present disclosure.

Referring initially toFIG. 2, shown therein is a distal core120of the intravascular device according to an embodiment of the present disclosure. As shown, the distal core120includes a proximal portion122having a generally cylindrical profile and a distal portion124having a generally rectangular profile. In some instances, the distal portion124is formed by flattening a portion of the distal core120that initially has a cylindrical profile. Generally, the distal portion124is configured to extend to a distal tip or end of the intravascular device. In some instances, a flexible element is positioned around the distal portion124of the distal core120, such as flexible element110described with respect toFIG. 1. The distal core120may be formed of any suitable material, including without limitation stainless-steel, nitinol, optical fiber, and/or other suitable material or combination of materials. In the illustrated embodiment, the distal core120is formed of stainless-steel.

Referring now toFIG. 3, an expander126is shown positioned around the proximal portion122of the distal core120. In particular, the expander126is positioned around the proximal portion122of the distal core120such that distal ends of the expander126and the proximal portion122are aligned along the length of the distal core120. However, such alignment is not required and, in other embodiments, the distal ends are offset along the longitudinal axis of the distal core120. The expander has a generally cylindrical profile and, serves to expand the radial diameter of the proximal portion122of the distal core120. To that end, in some instances the proximal portion122has a diameter between about 0.05 mm and about 0.15 mm, while the expander126has an inner-diameter slightly larger than proximal portion122and an outer-diameter between about 0.15 mm and about 0.35 mm. Further, the expander126has an axial length128. In some implementations, the axial length128of the expander126is between about 0.5 mm and about 6.0 mm. In some instances, the axial length128of the expander126is equal to the axial length of the proximal portion122. In other instances, the axial length128of the expander126is shorter or longer than the axial length of the proximal portion122. In some instances, the inner-diameter of the expander126extends the entire axial length128, while in other instances, the inner-diameter of the expander126does not extend the entire axial length128. The expander126may be formed of any suitable material, including without limitation stainless-steel, nitinol, optical fiber, and/or other suitable material or combination of materials. In some implementations, the expander126is formed, at least partially, of conductive material. The expander126is fixedly secured and sealed against pressure loss to the proximal portion122of the distal core120utilizing suitable techniques for the selected materials of the expander126and the proximal portion122of the distal core120. Accordingly, in some instances the expander126is fixedly secured to the proximal portion122of the distal core120by solder, weld, adhesive, swaging, and/or combinations thereof. In the illustrated embodiment, the expander126is formed of stainless-steel and is laser welded to the proximal portion122of the distal core120.

Referring now toFIG. 4, a tubular member130is shown positioned around the expander126. In that regard, the expander has a generally cylindrical profile and, therefore, further expands the radial diameter of the expander. To that end, in some instances the tubular member130has an inner-diameter slightly larger than the outer-diameter of expander126and an outer-diameter between about 0.15 mm and about 0.35 mm. In the illustrated embodiment, the tubular member130is positioned around the expander126such that distal ends of the tubular member130and the expander126are aligned along the length of the proximal portion122. However, such alignment is not required and, in other embodiments, the distal ends are offset along the longitudinal axis of the proximal portion122. Further, the tubular member130has an axial length132that may be greater than, equal to, or less than the axial length128of the expander126. In the illustrated embodiment, the axial length132of the tubular member130is greater than the axial length128of the expander126. In some implementations, the axial length132of the tubular member130is between about 0.5 mm and about 6.0 mm. As will be discussed in greater detail below, the increased length or axial offset of the tubular member130relative to the expander126allows a central lumen of the tubular member130to be only partially occupied by the expander126(and proximal portion122of the distal core120). In the illustrated embodiment, with the distal ends of the tubular member130and the expander126aligned and a tubular member130with an axial length132greater than the axial length128of expander126, a cavity is created in the central lumen equal to the difference between the axial length132and the axial length128. This open space in the lumen of the tubular member130is utilized to facilitate capacitive pressure measurements in some implementations of the present disclosure.

The tubular member130may be formed of any suitable material, including without limitation stainless-steel, nitinol, optical fiber, polymer, copper, gold, and/or other suitable material or combination of materials. In some implementations, the tubular member130is formed, at least partially, of conductive material. For example, in some instances the tubular member is formed first of a non-conductive material, then coated with a conductive material. In such instances, all or only portions of the tubular member may be coated with the conductive material. The tubular member130is fixedly secured to the expander126utilizing suitable techniques for the selected materials of the tubular member130and the expander126. Accordingly, in some instances the tubular member130is fixedly secured to the expander126by solder, weld, adhesive, pressed, swaged, and/or combinations thereof. In the illustrated embodiment, the tubular member130is formed of stainless-steel and is laser welded to the expander126. Thus, in the illustrated embodiment the tubular member130is electrically coupled to the expander126. In other embodiments, the tubular member130and the expander126are micro-molded as one device then welded, glued, soldered, pressed, swaged, and/or otherwise coupled to proximal portion122of the distal core120. Similarly, in some implementations a shape corresponding to the shape resulting from the tubular member130and the expander126is over-molded directly onto the proximal portion122of the distal core120. The over-molded materials can be conductive or non-conductive. If a non-conductive material is utilized, then a conductive coating could be applied as described above. Generally speaking, the assembly consisting of the distal core120, the expander126, and the tubular member130may be thought of as the substrate of an electrical device (like a printed-circuit board or flex-circuit) or an “anode” or static member of a capacitive sensor.

Referring now toFIG. 5, portions of the tubular member130and the expander126have been removed according to an embodiment of the present disclosure. In particular, a mounting structure134has been defined by removal of portions of the tubular member130and the expander126. The mounting structure134is sized and shaped to facilitate mounting and interconnection of one or more electrical, optical, and/or electro-optical components. Accordingly, the mounting structure134can take on virtually any shape desirable for mounting such components. In the illustrated embodiment, the mounting structure134has a generally rectangular profile with a planar bottom surface136bounded by a proximal wall138and distal wall opposite the proximal wall. As will be described below, the mounting structure134of the illustrated embodiment is sized and shaped to facilitate the mounting of an application-specific integrated circuit (ASIC), including electrical coupling of the ASIC to associated components of the intravascular device. Further, a plurality of openings140are formed in the tubular member130to provide access to the central lumen of the tubular member. Generally, any number of openings may be utilized, but in some instances between 1 and 20 openings are formed. In the illustrated embodiment, the openings140are formed annularly around the circumference of the tubular member130. In that regard, the openings may be equally spaced about the circumference, symmetrically spaced about the circumference, or irregularly spaced about the circumference. Further, in the illustrated embodiment the openings140have circular cross-sectional profiles. However, it is understood that the openings may have virtually any geometric (e.g., triangle, rectangle, square, circle, oval, ellipse, trapezoid, pentagon, hexagon, etc.) or non-geometric cross-sectional profile.

Generally, the portions of the tubular member130and the expander126may be removed using any suitable technique for the applicable material. For example, in some instances the portions of the tubular member130and the expander126are removed using laser, EDM, micro-drill, grinding, CNC, other suitable techniques, and/or combinations thereof. Further, it is understood that in some instances that portions of the tubular member130and/or the expander126are removed prior to assembly of the tubular member130onto the expander126and/or prior to assembly of the expander126onto the proximal portion122of the distal core120. Further still, in some instances a plurality of tubular members130are formed from a single elongated hypotube. In that regard, the single elongated hypotube may be cut into a plurality of sections, each having the axial length132. Also, the portions of tubular member130shown as being removed inFIG. 5may likewise be removed while in the form of the single elongated hypotube (e.g., by repeatedly removing the requisite portions along the length of the elongated hypotube at spacings necessary to form the plurality of tubular members) or after formation of the individual tubular member components. Likewise, a plurality of expanders126are formed from a single elongated hypotube in some instances. In that regard, the single elongated hypotube may be cut into a plurality of sections, each having the axial length128. Also, the portions of expander126shown as being removed inFIG. 5in the context of mounting structure134may likewise be removed while in the form of the single elongated hypotube (e.g., by repeatedly removing the requisite portions along the length of the elongated hypotube at spacings necessary to form the plurality of expanders) or after formation of the individual expander components.

Referring now toFIG. 6, a material142has been introduced into the lumen of the tubular member130to fill the open space within the tubular member130, including the central lumen and openings140. The material142forms a temporary structure that will be removed subsequently. Accordingly, the material142is formed of a material that can be chemically removed without damaging the tubular member130, expander126, and/or the proximal portion122of the distal core120in some instances. For example, in some instances the material142could be copper (Cu).

In some instances, the surface of tubular member130is precision center-ground and polished. Further, in some instances a precision groove is optionally cut or ground into the tubular member130. In that regard, the groove is sized and shaped to receive an annular band144described in greater detail below. Accordingly, in some instances the groove is formed prior to the introduction of material142such that the material142fills the groove. In some instances, the groove filled with the material142is precision center-ground and polished to be smooth such that it has the same outer diameter as the remaining portions of tubular member130.

Referring now toFIG. 7, an annular band144is formed around a portion of the tubular member130according to an embodiment of the present disclosure. In that regard, the annular band144extends annularly around the tubular member130in alignment with the openings140. In some embodiments, the annular band144is formed in a groove formed in the outer surface of the tubular member as discussed above. The annular band144is also a temporary structure that will be removed subsequently. Accordingly, the annular band144is formed of a material that can be chemically removed without damaging the tubular member130, expander126, and/or the proximal portion122of the distal core120in some instances. To that end, in some implementations the annular band144is formed of the same material as the temporary structure defined by material142. For example, in some instances the annular band144could be formed of copper.

Referring now toFIG. 8, a material layer146is formed over the tubular member130, expander126, and proximal portion122of the distal core120according to an embodiment of the present disclosure. Generally, the material layer146is formed of a flexible material suitable to act as a membrane for a capacitive pressure sensing arrangement as will described in further detail below. Accordingly, in some instances the material layer146is formed of a flexible, non-conductive polymer material. In some embodiments, the material layer146is formed of parylene, PDMS (Polydimethylsiloxane), and/or combinations thereof. Further, the material layer146has a thickness between about 0.001 mm and about 0.003 mm in some instances. In the illustrated embodiment, the material layer146is parylene having a thickness of approximately 0.0013 mm. In some instances, the material layer146extends over the distal portion124of the distal core120. In other instances, the distal portion124of the distal core120is masked and/or otherwise treated, protected, or avoided such that material layer146does not extend over the distal portion124.

Referring now toFIG. 9, a section of the material layer146extending around the tubular member130and portions of the tubular member130are shown in phantom to reveal the presence of the temporary structure142and the temporary annular band144after formation of the material layer146. With the material layer146formed, the temporary structure142and the temporary annular band144are chemically removed. In some embodiments, the temporary structure142and the temporary annular band144are removed immediately following formation of the material layer146. In other embodiments, one or more additional steps are performed after formation of the material layer146before the temporary structure142and the temporary annular band144are removed. For example, in some instances the formation of the electrode described in the context ofFIG. 14is performed prior to removal of the temporary structure142and the temporary annular band144.

Referring now toFIGS. 10-12, the material layer146, the tubular member130, the expander126, and the proximal portion122of the distal core120are shown after removal of the temporary structure142and the temporary annular band144according to an embodiment of the present disclosure. As best shown inFIGS. 11 and 12, with the temporary structure142and the temporary annular band144removed, the flexible material layer146is in communication with the central lumen148of the tubular member130via openings140. Further, the sections of the material layer146positioned adjacent to the openings140are spaced from the outer wall of the tubular member130by a distance equal to the thickness of the temporary annular band144that was removed. This spacing allows the material layer146to flex in response to pressure changes.

Referring toFIG. 13, a more detailed cross-sectional profile of the arrangement of the material layer146and tubular member130adjacent an opening140is shown. As illustrated, space150is provided between a lower surface152of the material layer146and the outer wall of the tubular member130adjacent the opening140. As noted above, the space150is defined by the thickness of the annular band144. In the illustrated embodiment, the annular band144had a width154that is greater than the diameter156of the opening140. In some instances, the width154is between about 0.1 mm and about 0.2 mm, while the diameter156is between about 0.1 mm and about 0.2 mm. The space150facilitates flexing of the material layer146in response to pressure changes and, in particular, relative changes in pressure between the environmental pressure surrounding material layer146and an ambient (if vented) or sealed central lumen148of the tubular member130. In some instances, the pressure within the central lumen148of the tubular member130is an atmospheric pressure. For example, in some instances the central lumen148is in communication with one or more additional lumens associated with the intravascular device that extend from the lumen148to an atmospheric pressure source. In other instances, the lumen148is sealed with a known and/or fixed pressure value.

Referring now toFIG. 14, an electrode158has been formed over a portion of the material layer146, and over the cavity formed by144. The width of electrode158may be greater than groove width154, equal to groove width154, or less than groove width154. In the illustrated embodiment, the width of158is greater than groove width154. Electrode158is formed of a conductive material, such as gold (Au), titanium/gold alloy (Ti/Au), and/or other suitable conductive material, and may consist of one or multiple layers of identical or varied materials. The electrode158may be formed by additive or subtractive methods. These methods include, but are not limited to: aerosol jet printing, ink-jet printing, powder-metal fabrication, laser-direct sintering, plating-etching, plating-laser ablation, and/or other suitable technique. In the illustrated embodiment, the electrode158includes and is in electrical communication with, an annular portion160that extends around the tubular member130, an axial portion162that extends along the major axis of the tubular member130, and a pad portion164that extends across the distal-most region of mounting structure134.

The annular portion160of the electrode158is fixedly attached to the outer surface of material layer146directly above the cavity formed by144. In some embodiments, the annular portion160is centered on the cavity formed by144, while in other embodiments, annular portion160is not centered on the cavity formed by144. A capacitor is formed from the annular portion160(cathode), the material layer146(dielectric), and the structure formed from120,126, and130(anode). With sufficient difference between the pressure surrounding the cavity formed by144and the ambient or sealed cavity pressure, the suspended material layer146and annular portion160will deflect—creating a variable capacitor. To facilitate this capacitive pressure sensing operation, in some embodiments the annular portion160of electrode158is centered upon the openings140and extends around the circumference of the tubular member130between about 25% and about 100% of the total circumference of the tubular member. As shown inFIGS. 15-18, in the illustrated embodiment the annular portion160of electrode158extends around a majority of the circumference of the tubular member130, but not completely around, such that a non-conductive section166of material layer146remains between the extents of annular portion160. In other instances, annular portion160of electrode158extends completely around the circumference of the tubular member130. In such instances, a dielectric patch or layer may be formed over a section of the annular portion160to define a non-conductive area similar to section166.

The axial portion162of the electrode158extends between annular portion160and pad portion164. In the illustrated embodiment, axial portion162of the electrode158is positioned on a side of the tubular member130substantially opposite section166. The pad portion164of the electrode158defines a pad site for an ASIC component that will be subsequently mounted within the mounting structure134. Accordingly, the axial portion162of the electrode158provides a conductive path between the annular portion160and the pad portion164such that changes in capacitance of the annular portion160can be conveyed to the ASIC component.

Referring now toFIG. 15, a section167of the material layer146within the mounting structure134has been removed (e.g., using laser ablation or other suitable technique) to expose a ground pad168on the expander126and proximal portion122of distal core120. Section167defines a bond pad for the ASIC component that will be subsequently mounted within the mounting structure134. Further, a flexible elongate member170is coupled to a proximal portion of the tubular member130. In the illustrated embodiment, a distal portion of the flexible elongate member170is positioned within the lumen148of the tubular member130. However, the distal portion of the flexible elongate member170is positioned within the lumen such that it is spaced proximally from the openings140in the tubular member130so as to not block the material layer146and annular portion160of the electrode158from having access to the lumen pressure through the openings140. In some implementations, the lumen148of the tubular member130includes a counter bore, shoulder(s), and/or other suitable engagement structures to ensure that the distal portion of the flexible elongate member170is properly positioned within the tubular member130without blocking the openings140.

In some implementations, the flexible elongate member170is a tubular member having a lumen extending along its length. To that end, the lumen of the flexible elongate member170is in communication with the lumen148of the tubular member130such that the lumen of the flexible elongate member170, alone or in combination with other elements, can be used to expose the lumen148to a reference pressure source, such as atmospheric pressure and/or a known pressure value. In some embodiments, the flexible elongate member170is a solid wire and therefore does not reference atmospheric pressure. The flexible elongate member170may be formed of any suitable material, including without limitation stainless-steel, nitinol, optical fiber, ceramic, and/or other suitable material or combinations thereof. In some implementations, the flexible elongate member170is formed, at least partially, of conductive material. For example, in some instances the tubular member is formed of a non-conductive material coated with a conductive material. In such instances, all or only portions of the tubular member may be coated with the conductive material. The flexible elongate member170is fixedly secured to the tubular member130utilizing suitable techniques for the selected materials of the flexible elongate member170and the tubular member130. Accordingly, in some instances the flexible elongate member170is fixedly secured to the tubular member130by solder, weld, adhesive, pressing, swaging, and/or combinations thereof. In the illustrated embodiment, the flexible elongate member170is formed of stainless-steel and is laser welded to tubular member130as indicated by weld line172. In the illustrated embodiment the flexible elongate member170is electrically coupled to the tubular member130. In some implementations, the elongate member170, tubular member130, and associated electrically coupled portions of the device carry a ground signal.

In some instances, the flexible elongate member170includes an outer insulating coating (e.g., a parylene layer or other suitable insulating material) along a majority of its length. In some instances, the insulating coating is applied after the flexible elongate member170is coupled to the tubular member130. In other instances, the insulating coating is applied prior to the flexible elongate member170being coupled to the tubular member130. To that end, in some instances one or more sections of the flexible elongate member170are masked, treated, and/or avoided to prevent application of the insulating coating. For example, the section of the flexible elongate member170that is welded to the tubular member130may not include an insulating coating after the procedure, and/or a proximal section of the flexible elongate member170that is used to define an electrical connector (or be coupled to an electrical connector) may not include an insulating coating. Alternatively, in some instances an insulating coating is applied to the entire flexible elongate member170and then sections of the insulating coating are removed, as necessary, to expose underlying portions of the flexible elongate member170.

Referring now toFIG. 16, a dielectric patch174is formed over the weld line172. As shown, the dielectric patch174is generally aligned with the section166of material layer146separating the ends of the annular portion160of the electrode158. For embodiments where the annular portion160of the electrode158extends completely around the tubular member130, the dielectric patch174can extend across both the weld line172and the annular portion160. Alternatively, two different dielectric patches could be formed across the weld line172and the annular portion160, respectively, for embodiments where the annular portion160of the electrode158extends completely around the tubular member130. The dielectric patch can be formed of any suitable dielectric material such as Parylene, PDMS, or other suitable dielectric material. The dielectric patch174and section166serve to electrically isolate an electrode176(See,FIG. 17) from the electrode158and the tubular member130.

Referring now toFIG. 17, an electrode176has been formed over a portion of the material layer146surrounding the tubular member130according to an embodiment of the present disclosure. The electrode176is formed of a conductive material, such as gold (Au), titanium/gold alloy (Ti/Au), and/or other suitable conductive material, and may consist of one or multiple layers of identical or varied materials. The electrode176may be formed by additive or subtractive methods. These methods include, but are not limited to: aerosol jet printing, ink-jet printing, powder-metal fabrication, laser-direct sintering, plating-etching, plating-laser ablation, etc. In the illustrated embodiment, the electrode176includes and is in electrical communication with, a ring pad178that is formed on the proximal end of tubular member130, an axial portion180that extends along the major axis of the tubular member130, and a pad portion182that extends across the proximal-most region of mounting structure134.

The ring pad178of the electrode176extends around the circumference of the tubular member130between about 25% and about 100% of the total circumference of the flexible elongate member170. In the illustrated embodiment, the ring pad178of electrode176extends completely around the circumference of the flexible elongate member170. The axial portion180of the electrode176extends between ring pad178and pad portion182. In the illustrated embodiment, axial portion180of the electrode176is positioned on a side of the tubular member130substantially opposite axial portion162of electrode158. To that end, the axial portion180extends across dielectric patch174and section166of the material layer146such that the electrode176is electrically isolated from the electrode158and the tubular member130. The pad portion182of the electrode176defines a further pad site for the ASIC component that will be subsequently mounted within the mounting structure134. Accordingly, the pad portion182of the electrode176provides a conductive path between the ring pad178and the pad portion182.

Referring now toFIG. 18, a conductive material (e.g. conductive adhesive, conductive film, solder paste, solder balls, etc.) is applied to the pad sites on mounting structure134. In the illustrated embodiment, conductive adhesive is applied to pad portion164of electrode158, ground pad168on expander126, and pad portion182of electrode176to facilitate mounting of an ASIC within the mounting structure134such that the ASIC is electrically coupled to the pad sites. As shown, adhesive184is applied to pad portion164of electrode158, adhesive186is applied to ground pad168on expander126, and adhesive188is applied to pad portion182of electrode176. Generally, any suitable conductive adhesive may be utilized. In some instances, the adhesive is silver-epoxy.

Referring now toFIG. 19, an ASIC module190has been mounted within the mounting structure134and electrically coupled to pad portion164of electrode158, ground pad168on expander126, and pad portion182of electrode176by the conductive adhesives184,186,188, respectively. In some instances, the ASIC module190may be one or more components and may include one, several, or all of the capabilities related to memory storage, signal conditioning, wireless communication interface, etc. The memory element may store information about the characteristics and use of the sensor. In some instances, the memory element stores device-specific information such as: device ID, usage limit, sensor ID, temperature coefficient, zero offset, scale factor, sensitivity, manufacture date, manufacture time, and manufacture location. In addition, the memory element may store information related to one or more specific periods of device activation or use, such as: count, date, time, location, system ID, pressure minimum, pressure maximum, velocity minimum, velocity maximum, temperature minimum, temperature maximum, and centered (y/n). The ASIC module190is energized via VCC from pad portion164and ground from ground pad168. With the ASIC module190mounted within the mounting structure134, the spacing around the ASIC module190can be filled in using under-filling and/or over-molding to further secure the ASIC module190in place and/or return the outer profile of the device to a cylindrical form such that it has generally constant outer profile along the length of the tubular member130.

Referring now toFIG. 20, a conductive layer192is formed over the material layer146such that the conductive layer covers all but an insulating band portion194at the proximal-most portion of insulating material layer146. As shown, the proximal-most portion of insulating material layer146defining insulating band portion194is spaced from the proximal-most portion of flexible elongate member170such that a conductive band196is defined. As discussed above, in some instances the flexible elongate member170serves as a ground source such that the conductive band196is a ground band.FIG. 20also illustrates an opening to the lumen198of the flexible elongate member170at the proximal end of the flexible elongate member170. In some instances, the material layer146defining insulating band portion194and/or the conductive layer192of the flexible elongate member170are formed prior to the assembly of the flexible elongate member with any other components of the intravascular device. In this manner, the flexible elongate member170may be a separate sub-assembly to streamline manufacturing procedures.

Referring now toFIG. 21, a conductive spacer200is positioned around the distal portion of the flexible elongate member170adjacent to the proximal end of the tubular member130. In that regard, the conductive spacer includes a conductive material on at least its distal end surface to electrically couple to the ring pad178of electrode176and its inner surface to electrically couple to the conductive layer192. An electrically conductive adhesive (such as silver-epoxy) is utilized in some instances to secure the conductive spacer200to the electrode176and/or the conductive layer192. In other instances, the conductive spacer200is electrically coupled and secured to the electrode176and/or the conductive layer192using conductive film. In an alternate embodiment, ring pad178and conductive layer192are direct-printed as one continuous, and electrically connected structure.

Referring now toFIG. 22, a flexible element204is positioned around a distal portion of the flexible elongate member170adjacent to the conductive spacer200. In particular, a distal end of the flexible element204abuts a proximal end of the conductive spacer200. In some embodiments, the outer-diameter of the conductive spacer200is smaller than the inner-diameter of the flexible element204or contains external threads or protrusions that allow the flexible element204to slide or thread onto the conductive spacer200. The flexible element204is fixed to the conductive spacer200with a suitable adhesive. The flexible element204is similar to the proximal flexible element109discussed in the context ofFIG. 1. Further, the flexible element204has a generally cylindrical outer profile and, therefore, further expands the radial diameter of the flexible elongate member170. To that end, in some instances the flexible element204has an outer diameter generally equal to the sensor region202(about 0.36 mm).

Similarly, in a previous or subsequent step, another flexible element is positioned around the distal portion124of the distal core120in a manner similar to the distal flexible element110discussed in the context ofFIG. 1. This distal flexible element also has a generally cylindrical outer profile and, therefore, further expands the radial diameter of the distal portion124of the distal core120. To that end, in some instances the distal flexible element110has an outer diameter generally equal to the sensor region202(about 0.36 mm). In the illustrated embodiment, the distal-most tip105of the distal flexible element110is radiopaque. The radiopaque tip is generally round to facilitate navigation while minimizing tissue damage while manipulating the intravascular device through the vasculature.

Referring now toFIG. 23, a conductive tubular member206is positioned over the conductive layer192of the flexible elongate member170. As shown, a distal end of the conductive tubular member206abuts a proximal end of the flexible element204, while a proximal end of the conductive tubular member206terminates adjacent to the insulating band portion194of the flexible elongate member170. Further, the conductive tubular member206has a generally cylindrical outer profile and, therefore, further expands the radial diameter of the flexible elongate member170. To that end, in some instances the conductive tubular member206has an outer generally equal to the sensor region202(about 0.36 mm).

The conductive tubular member206may be formed of any suitable conductive material, including without limitation stainless-steel, nitinol, and/or other suitable conductive material. In some implementations, conductive tubular member206is formed of a non-conductive material, then coated/plated with a conductive material. In such instances, all or only portions of the tubular member may be coated with the conductive material. The conductive tubular member206is fixedly secured and electrically coupled to the conductive layer192of the flexible elongate member170utilizing suitable techniques for the selected materials of the conductive tubular member206and the conductive layer192. Accordingly, in some instances the conductive tubular member206is fixedly secured to the flexible elongate member170by conductive adhesive, swaging and/or combinations thereof. In the illustrated embodiment, the conductive tubular member206is formed of stainless-steel and is coupled to the flexible elongate member170by conductive adhesive. Thus, in the illustrated embodiment the conductive tubular member206is electrically coupled to the conductive layer192, the conductive spacer200, and the electrode176.

Referring now toFIG. 24, an insulating layer208is formed over the conductive tubular member206along a majority of the length of the conductive tubular member. In some instances, the insulating coating is applied after the conductive tubular member206is coupled to the conductive layer192of flexible elongate member170. In other instances, the insulating layer208is applied prior to the conductive tubular member206being coupled to the flexible elongate member170. To that end, in some instances one or more sections of the conductive tubular member206are masked, treated, and/or avoided to prevent application of the insulating coating. For example, in the illustrated embodiment the insulating layer208does not extend over a section210at the proximal end of the conductive tubular member206. In that regard, in some implementations the section210defines an electrical connector similar to conductive band114of connector111discussed in the context ofFIG. 1. Alternatively, in some instances the insulating coating is applied to the entire conductive tubular member206and then sections of the insulating coating are removed, as necessary, to expose underlying portions of the conductive tubular member206.

Referring now toFIG. 25, an insulating spacer212is positioned over insulating band portion194of the flexible elongate member170according to an embodiment of the present disclosure. As shown, a distal end of the insulating spacer212abuts a proximal end of the conductive tubular member206, while a proximal end of the insulating spacer212terminates adjacent to the distal extent of ground band196of the flexible elongate member170. The insulating spacer212has a generally cylindrical outer profile and, therefore, further expands the radial diameter of the flexible elongate member170. To that end, in some instances the insulating spacer212has an outer diameter generally equal to the sensor region202(about 0.36 mm). The insulating spacer212may be formed of any suitable insulating material, including without limitation PP/PE/PA/PC/ABS. The insulating spacer212is fixedly secured to the flexible elongate member170utilizing suitable techniques for the selected materials of the insulating spacer212and the insulating material of insulating band portion194of the flexible elongate member170. Accordingly, in some instances the insulating spacer212is fixedly secured to the flexible elongate member170by an adhesive. In other instances, the insulating spacer212is not itself fixedly secured to the flexible elongate member, but is positioned between components that are fixedly secured, such as conductive tubular member206and conductive sleeve214(See,FIG. 26). In the illustrated embodiment, the insulating spacer212is formed of PP and is not fixedly coupled to insulating band portion194on the flexible elongate member170.

Referring now toFIGS. 26 and 27, a conductive sleeve214is positioned over ground band196at the proximal extent of flexible elongate member170. As shown, a distal end of the conductive sleeve214abuts a proximal end of the insulating spacer212, while a proximal end of the conductive sleeve214terminates adjacent to proximal end of the flexible elongate member170. Further, the conductive sleeve214has a generally cylindrical outer profile and, therefore, further expands the radial diameter of the flexible elongate member170. To that end, in some instances the conductive sleeve214has an outer diameter generally equal to the sensor region202(about 0.36 mm).

The conductive sleeve214may be formed of any suitable conductive material, including without limitation gold (Au), titanium-gold (Ti/Au), platinum-iridium (PtIr), and/or other suitable conductive material. In some implementations, conductive sleeve214is formed of a non-conductive material then coated with a conductive material. In such instances, all or only portions of the tubular member may be coated with the conductive material. The conductive sleeve214is fixedly secured and electrically coupled to the conductive ground band196of the flexible elongate member170utilizing suitable techniques for the selected materials of the conductive sleeve214and the conductive ground band196of the flexible elongate member170. Accordingly, in some instances the conductive sleeve214is fixedly secured to the flexible elongate member170by solder, weld, conductive adhesive, pressing, swaging, and/or combinations thereof. In the illustrated embodiment, the conductive sleeve214is formed of PtIr and is coupled to ground band196of the flexible elongate member170by swaging. Thus, in the illustrated embodiment the conductive sleeve214is electrically coupled to the flexible elongate member170, tubular member130, and expander126, which is electrically coupled to the ASIC module190via ground pad168.