Patent Description:
This application relates to implant packages and more particularly to an implant for optimal wireless communication.

Implantable wireless sensors are useful in assisting diagnosis and treatment of many diseases. Examples of wireless sensor readers are disclosed in <CIT>, and <CIT>, each entitled Wireless Sensor Reader. Delivery systems for wireless sensors are disclosed in PCT Patent Application No. <CIT> entitled Pressure Sensor, Centering Anchor, Delivery System and Method. In particular, there are many applications where measuring pressure from within a blood vessel deep in a patient's body is clinically important. For example, measuring the pressure in the heart's pulmonary artery is helpful in optimizing treatment of heart failure and pulmonary hypertension. In this type of application, a sensor may need to be implanted <NUM> to <NUM> beneath the surface of the skin.

Implantable wireless sensors that use radiofrequency (RF) energy for communication and power have been found to be particularly useful in medical applications. However, there are many tradeoffs and design constraints in designing such implantable sensors, such as size, cost and manufacturability.

A key challenge in successful commercialization of these implantable wireless sensors is the design tradeoff between implant size and the "link distance", which is the physical distance between the implant and the external device communicating with or providing energy to the implant. From a medical standpoint, it is desirable for an implant to be as small as possible to allow catheter based delivery from a small incision, implantation at a desired location, and a low risk of thrombosis following implant. However, from a wireless communication standpoint, the smaller the implant, the shorter the link distance. This distance limitation may be a function of the size of the antenna that can be realized for a given overall implant size. A larger antenna may be able to absorb more RF energy and transmit more RF energy than a smaller antenna. For example, in the case of wireless communication via inductive coupling, a typical implant antenna has the form of a coil of wire. The coil's "axis" is the line that extends normal to the plane of the windings, i.e. the axis is perpendicular to the wire's length. As the area encircled by the coil increases, the amount of magnetic flux that passes through it generally increases and more RF energy is delivered to / received from the implant. This increase in flux through the implant antenna can result in an increase in link distance. Thus to achieve maximum link distance for a given implant size, the implant antenna should be of maximal size.

While antenna size is important, other implant architectures may benefit from maximizing the size of other internal components. An implant containing an energy storage device such as a battery, for example, would enjoy longer battery lifetime with a larger battery. In another example, a drug-eluting implant could hold a larger quantity of the drug. Other examples will be apparent to those skilled in the art. Thus, it may be generally advantageous for an implant to have the largest possible internal volume, while maintaining the smallest possible external dimensions. This objective may be constrained by the implant's need for a strong, biocompatible, and hermetically sealed housing, to protect the internal volume from liquid ingress from the body environment.

Moreover, an optimal implantable sensor may be best designed to function with a specific device or reader device. Wireless transmitter and reader devices, such as the wireless reader of <CIT> and <CIT> entitled "WIRELESS SENSOR READER," as well as <CIT> entitled "WIRELESS SENSOR READER (SENSOR BANDWIDTH BASED ON AMBIENT CONDITION) may require a specific implantable sensor to provide optimal functionality of the reader/sensor system. An optimal implantable sensor for such systems may be configured to transduce pressure into an electrical resonant frequency. The sensor may be a passive sensor with no internal power source, such as a sensor having an LC resonant tank circuit. The sensor may minimize its total size while maximizing coil area, as described in PCT Patent No. <CIT> entitled "IMPLANTABLE SENSOR ENCLOSURE WITH THIN SIDEWALLS". The sensor may have a high RF Quality factor (Q), which is maximized by careful materials selection and device design. The sensor may be immune to temperature changes, including temperature changes during the manufacturing process and in transition between ambient conditions and in vivo. The sensor may have high sensitivity and good electrical isolation between electrical nodes and surrounding body fluids or tissue. The sensor may be highly stable over time, have good mechanical strength, incorporate biocompatible materials, and minimize use of ferritic materials. The sensor may be hermetically sealed to keep blood and other liquids from the body environment away from the internal electronics, possibly for the lifetime of the patient.

For an LC type wireless MEMS sensor, overcoming these challenges requires the design of a small sensor with high RF Quality factor (Q) at low operating frequencies (the human body attenuates wireless data signals, with generally more signal attenuation occurring at higher frequencies above <NUM>). Additional challenges arise due to regulatory policies and licensed frequency bands for commercial use. With current technology, it is difficult to reliably fabricate an accurate ultra-miniature implantable wireless pressure sensor with high Q factor at low operating frequencies within a tightly controlled operating range.

Patent document <CIT> from the same applicant describes a solution of an implant according to which a diaphragm vertically overlaps a base, whereby both radially fit in lateral walls of the housing. Such an assembly however involves delicate bonding areas both inside and on top of the lateral horizontal walls of the housing in order to ensure the hermeticity of the implant, which are difficult to realize effectively. Patent document <CIT> describes another implant including a wafer closing lateral walls, and on which electrodes are provided through etching on the inside of the housing. This solution involves yet no base attached to a horizontal wall of the housing an protruding inside of it for arranging further electronic components.

To improve implantable wireless sensors, it is desirable to optimize various features of the sensor implant to ensure a high resonant quality factor may occur over the life of the implant.

This application relates to hermetically packaged wireless electronics and more particularly to an implantable sensor design and manufacturing approach to optimize manufacturability, size, longevity, RF characteristics, and overall performance.

In an embodiment, provided is an implant comprising a housing that defines a cavity. A sensor is connected to the housing. The sensor includes a diaphragm and a hanging base. The hanging base is attached to the diaphragm wherein the hanging base is positioned entirely within said cavity. The hanging base may be attached only to said diaphragm. The sensor is a capacitive sensor. The diaphragm may be connected to the housing to form part of a hermetic seal about the cavity. The sensor includes electrical contacts such as electrodes positioned on said diaphragm. The hanging base may define a capacitive gap and a vent. The hanging base and said diaphragm define the capacitive gap wherein an attachment between the hanging base and the diaphragm includes a discontinuity that allows at least one electrical trace or electrode to connect outside the capacitive gap to at least one electrode positioned at least partially within the capacitive gap. The discontinuity may be a vent to allow the passage of fluid between the cavity and the capacitive gap. A coil may be in electric communication with said sensor and be positioned within said housing. The coil may include a coil axis wherein the coil axis may be substantially perpendicular to said diaphragm. A printed circuit board may be attached to the hanging base and may include at least one electronic component. The electronic component may be a capacitor whose capacitance value may be adjusted by laser trimming, wherein said laser passes through said housing to perform the trimming. Implant parameters may be adjusted after hermetic sealing is complete by transmitting radiation through the housing to inside the cavity. The radiation may be one of laser, ultraviolet light, infrared light, focused light, and gamma radiation. The implant parameters that are adjusted may be performed by at least one of: ablating portions of electrodes on said sensor; ablating portions of a capacitor; ablating portions of tracks on a substrate; curing an adhesive; curing a coating; modifying an optically sensitive chemical; activating a thermally sensitive chemical; attaching items by welding; separating items by cutting; ablating a coating, film, or structure; and causing solder to reflow.

In another embodiment, provided is a method of making an implant. The method includes providing a housing that defines a cavity. A hanging base is attached to a diaphragm to form a sensor. The diaphragm is attached to said housing such that said hanging base is positioned within said cavity. A coil is attached to said sensor. A bottom is attached to said housing to form a hermetic seal about the cavity. A plurality of side walls may be welded together to provide said housing that defines said cavity. Alternatively, a continuous material may be machined to provide said housing that defines said cavity. The floating base may be made of a different material than said diaphragm. The diaphragm may be hermetically attached to said housing by a first laser weld about the perimeter of said cavity and a second laser weld about the perimeter of said cavity. The housing may include an integral base. The sensor comprises a diaphragm having at least one diaphragm electrode and a base attached to the diaphragm. The base includes at least one base electrode wherein said base and diaphragm define a capacitive gap between the at least one diaphragm electrode and the at least one base electrode. The base may include a perimeter that is larger than a perimeter of the diaphragm such that the base attaches to the housing to define the cavity. The base may include at least one "Through Substrate Via" (TSV) to electrically connect the at least one of the base electrode and the diaphragm electrode to a component outside the capacitive gap. The base is a hanging base positioned within the cavity of said housing. The diaphragm may include a thick region and a thin region wherein the thin region is aligned with said capacitive gap between the at least one diaphragm electrode and the at least one base electrode. A coil may be in electric communication with said sensor, said coil may be positioned within said housing. A printed circuit board having at least one electronic component may be attached to the base and electrically attached to said coil. A distal anchor and a proximal anchor opposite the distal anchor may extend from the housing wherein the distal anchor and proximal anchor may form loops that extend from the implant. The anchors may be positionable in a fold down configuration and deployable from the fold down configuration to an open configuration. The proximal and distal anchors may be made of at least one of nitinol, platinum, stainless steel, polymer, and material which is biocompatible and extrudable. The sensor may be at least one of a pressure sensor, a temperature sensor, a gas sensor, and strain gauge. The housing may be attached to the diaphragm by at least one of laser welding, frit bonding, anodic bonding, fusion bonding, and eutectic bonding. The sensor may be electrically attached to the electronics wherein the electrical attachments are accomplished by at least one of wirebonding, soldering, ultrasonic bonding, wedge bonding, laser welding, and conductive adhesives. The implant may be an actuator and may include an energy storage unit within the cavity. The energy storage unit may be at least one of an electrochemical cell and a supercapacitor. An internal component may be provided within said cavity, the internal component may be a drug, a steroid, a battery, a stimulus electrode, a pacing circuitry, a flow sensor, or a chemical sensor. The implant may communicate wirelessly with an external unit. The implant may include a circuit having a resonant frequency that changes in response to a sensed parameter. The implant may include a circuit functional to perform at least one of modulation, demodulation, memory, ac/dc conversion, and signal conditioning. The diaphragm is made of a non-conductive material. The PCB may include at least one chip-scale pressure sensor wherein the chip-scale pressure sensor communicates with the diaphragm through an internal pressure of said cavity.

Embodiments of the present disclosure are described herein with reference to the drawings wherein:.

Reference will now be made in detail to embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. It is to be understood that other embodiments may be utilized and structural and functional changes may be made without departing from the respective scope of the invention, which is defined by the appended claims.

This application relates to an implant <NUM> and more particularly to an implantable sensor design and manufacturing approach to optimize manufacturability, size, longevity, RF characteristics, Q, and overall performance. To maximize RF link distance for a given implant size, the implant housing may be constructed to maximize antenna coil area, while still providing ample protection from the environment.

The implant <NUM> may include a housing <NUM> that may utilize thin membrane materials such as glass, quartz, sapphire, fused silica, alumina, titanium, diamond, or other materials, to increase the space available inside an implant package of a fixed outer size. Materials with low electrical conductivity may be used to prevent RF shielding of electromagnetic energy from the external unit, needed to power the implant, as well as the RF signal that is emitted by the implant. Electrically conductive or partially conductive housing materials may also be considered for systems in which power or signal transfer are at high frequencies, or implemented using other wireless energy transfer means such as ultrasonic, acoustic, et al.

<FIG>, <FIG>, and <FIG> illustrate a wireless implant housing <NUM> that maximizes coil area by its wall arrangement. The implant <NUM> may have an elongated, narrow, rectangular shape, although the housing may have various shapes and geometry. <FIG> illustrates an embodiment of the implant <NUM> in top perspective view and <FIG> and <FIG> illustrate an embodiment of the implant <NUM> in cross section. The dimension of the housing <NUM> may be generally cuboid and may define a cavity <NUM> therein. The housing side walls may be of specific dimensions and proportions to each other. For example, the housing may have four side walls <NUM>, <NUM>, <NUM>, and <NUM>, a top wall <NUM> and a bottom wall <NUM>. The housing <NUM> may be made of a hermetic, strong, and biocompatible material, such as ceramic. The housing <NUM> may be fabricated with processes, including micromachining, ultrasonic machining, wet etching, plasma etching, laser machining, conventional tool machining, injection molding, powder molding, or electrical discharge machining (EDM). The examples illustrate a cuboid housing, but other shapes and configurations may be used, such as cylindrical housings, prism-shaped housings, octagonally or hexagonally cross-sectioned housings, or the like. Additionally, any combination of walls <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> may be machined or molded as a single piece. For example, sidewalls <NUM>, <NUM>, <NUM>, and <NUM> may be machined as a single piece and top wall <NUM> and bottom wall <NUM> may be created separately and then assembled to create the housing <NUM>.

A distal anchor <NUM> and a proximal anchor <NUM> opposite the distal anchor may extend from the top side of the implant <NUM>. The anchors may fixate the implant <NUM> in a desired position in the body of the patient and prevent it from moving. Notably, other anchor configurations and shapes may be implemented, including a different number of anchors (other than two); different locations of anchor attachment to the housing; anchors which attach to the housing at one point, or more than two points; anchors that extend under the housing, around it, or laterally to the sides; anchors with multiple loops or coils; and others. The anchors may be formed as loops which anchor the implant to body structures using spring force, or they may be designed to penetrate body tissues. The anchors may be made of nitinol, stainless steel, polymer, or any material which is biocompatible and extrudable. The anchors may be made of a combination of materials, such as nitinol with a platinum core. The anchors may be configured to fold down during the implantation procedure to allow easy ingress to the deployment location. The anchors may be configured to be tied down to a delivery system, such as a catheter, for minimally invasive ingress to the Implant deployment site. The anchors may be designed to deploy from their tied-down configuration to their open configuration when an operator actuates a control on the proximal end of the delivery system. The control may include release wires that are pulled from the proximal end either directly or with help from a mechanical handle. The anchors may be coated with a material to increase lubricity.

<FIG> illustrates the sensor <NUM> which may comprise one component of the implant <NUM>. The sensor <NUM> may include the top wall <NUM> having electronic components placed thereon. The top wall <NUM> may be a diaphragm once bonded together with the remaining side walls. The sensor <NUM> may be Micro Electromechanical Systems (MEMS) type sensor. The sensor <NUM> may be a capacitive type sensor, formed by attaching a base <NUM> to the diaphragm <NUM>. In one embodiment, a capacitive gap <NUM> may be positioned between the base <NUM> and the diaphragm <NUM>. At least one of the base <NUM> and the diaphragm <NUM> may be etched to create the capacitive gap <NUM> at least partially between the base <NUM> and the diaphragm <NUM>. Electrodes 46A, 46B may be patterned on either side of the capacitive gap <NUM> (See Figure. The electrode 46A may be placed on the diaphragm <NUM> and electrode 46B may be placed on the base <NUM>. Electrode 46A may terminate to bond pads 42A, 42B which may be available to connect the electrode 46A to other components in the implant <NUM>. The capacitive gap <NUM> may be vented to the outside of the sensor <NUM> by vent <NUM>. The vent <NUM> may be a break in the bond or weld line between base <NUM> and diaphragm <NUM>, which allows electrical traces or interconnect of the electrodes 46A to pass through and connect bond pads 42A, 42B. The attachment configuration between the base <NUM> and the diaphragm <NUM> may define a discontinuity that allows at least one electrical trace to connect outside said capacitive gap to at least one electrode positioned at least partially within the capacitive gap. The discontinuity may be the vent <NUM>. The vent <NUM> may also allow the passage of fluid between the cavity <NUM> and the capacitive gap <NUM>.

The underside <NUM> of the diaphragm <NUM> may be bonded to the base <NUM>. Processes for this include laser welding, anodic bonding, fusion bonding, eutectic bonding, and glass frit bonding. Etching processes utilized for forming the sensor <NUM> include wet etching, dry etching, plasma etching, deep reactive ion etching (DRIE), laser machining, conventional machining, and ultrasonic machining. Possible electrode patterning processes include liftoff, sputtering, and laser machining. The sensor <NUM> may be a capacitive pressure sensor, wherein the diaphragm <NUM> may be designed to flex slightly and change the height of gap <NUM> when the top surface <NUM> and bottom surface <NUM> of sensor <NUM> are exposed to different pressures. The sensor <NUM> may be a force or strain sensor, wherein the diaphragm <NUM> may be designed to flex and change the gap <NUM> height when exposed to force or strain. The sensor <NUM> may be a temperature sensor, wherein the diaphragm <NUM> and base <NUM> may be made of different materials, designed to expand at different rates when exposed to temperature, and thus vary the gap <NUM>. The sensor <NUM> may be an accelerometer, wherein the base <NUM> acts as a proof mass and changes the gap <NUM> height in response to acceleration or vibration. Electrodes 46A and 46B may include various discontinuities, such as slots or holes, in their patterning, to reduce losses due to eddy currents.

Minor variations to the basic design of the sensor <NUM> may be effected, to create other sensor types. Removing the base <NUM> may create a chemical sensor or a proximity sensor, wherein the top electrodes 46A may form an in-plane capacitor whose capacitance changes when the dielectric constant of the environment outside the top plate <NUM> changes, or when an object that affects capacitance (for example a metal object) gets sufficiently close to top plate <NUM>. Patterning piezoresistive transducing elements onto diaphragm <NUM> may form a resistive type of sensor, which may transduce changes in diaphragm shape due to pressure, temperature, or strain into resistive changes. In such cases the base <NUM> may be eliminated; retaining the base <NUM> as a proof mass but eliminating electrode 46B may creates a sensor type that transduces acceleration into resistance.

The sensor <NUM> architectures includes a large overlapping area of the perimeter of the diaphragm <NUM> relative to the base <NUM>. This feature may assist with the assembly of the implant <NUM>. The base <NUM> and the diaphragm <NUM> may have various thicknesses and this disclosure is not limited. In one embodiment, the base <NUM> may be between <NUM> to <NUM> thick. The diaphragm <NUM> may be about <NUM> to <NUM>. As illustrated by <FIG>, the "floating base" <NUM> includes a configuration having an area that substantially underlaps and hangs from the diaphragm <NUM>. In an embodiment, the diaphragm may be about <NUM> thick. The diaphragm thickness may be selected to be structurally strong enough to form the top wall of the implant <NUM>, and be stiff to minimize the amount of stiffness change caused by cell growth on the outer surface of the diaphragm. In an embodiment, the floating base <NUM> may be about <NUM> to <NUM> thick.

The diaphragm <NUM> and base <NUM> may be made from the same material or from different materials that are amenable to bonding and whose difference in thermal expansion coefficient may be such that the desired thermal properties may be obtained (either thermal stability or a known response to thermal changes). Materials for the diaphragm <NUM> and the base <NUM> may include glass, fused silica, quartz, sapphire, diamond, ceramic, silicon and its derivatives, germanium, SiGe and its derivatives.

The sensor <NUM> may be fabricated on wafer scale by a MEMS process. These components may be generally modular wherein a plurality of MEMs components and floating bases <NUM> may be manufactured along a single wafer.

<FIG> is a cross sectional sketch of an assembled implant <NUM> showing some of its constituent parts. In <FIG>, the bottom wall <NUM>, side walls <NUM>, <NUM>, <NUM>, <NUM>, and top wall <NUM> may be bonded together to form the housing <NUM> that defines the cavity <NUM>. It will be appreciated that the walls may be hermetically bonded or sealed in any appropriate manner such as by welding, brazing, frit bonding, frit welding, eutectic bonding, anodic bonding, fusion bonding, or others. The side wall thicknesses of the housing walls are non-limited but may be thinner than the bottom wall <NUM> and the top wall <NUM>. The side walls <NUM>, <NUM>, <NUM>, and <NUM> may be attached to one another to form the cavity therein before the top wall <NUM> and bottom wall <NUM> to allow for various components to be placed therein. Alternatively, side walls <NUM>, <NUM>, <NUM>, and <NUM> may be machined monolithically, in a generally continuous configuration, as a single four-sided unit, with an open top and bottom, and the top and bottom walls attached later. It may be etched or machined from a solid slab of material.

<FIG> is a flowchart that illustrates an exemplary method for assembling the implant <NUM>. <FIG> represents one possible process for a typical embodiment of the implant <NUM>. Some steps may not be necessary, or can be carried out in a different sequence, or may include other steps. <FIG> illustrate embodiments of assembling the sensor implant <NUM> that may be associated with the flowchart of <FIG>.

In step <NUM>, a housing may be formed having four sides <NUM>, <NUM>, <NUM>, and <NUM>. However, this disclosure is not limited as other shaped housings <NUM> are contemplated, such as cylindrical, triangular, pentagonal, hexagonal, or any shape, including asymmetrical configurations. The side walls, top wall, and bottom wall may be thinner than a design in which some or all of the housing is fabricated monolithically by a machining process. The walls of the housing <NUM> may be thinned by polishing, etching, or other methods and separately attached to one another to form the housing <NUM> and the cavity <NUM>.

The sensor <NUM> may be fabricated as a standalone device, described by step <NUM>. This may allow the sensor <NUM> to be screened by test or inspection before assembly into the implant <NUM>. In-line screening tests and inspections at may actually occur along any point in the process to allow scrapping of unacceptable sensors <NUM> and prevent waste.

The sensor <NUM> may be attached to the housing <NUM> per step <NUM>. <FIG> and <FIG> illustrate the sensor <NUM> attaches to the sidewalls <NUM> and <NUM> of the housing <NUM>, such that the floating base <NUM> resides inside the cavity <NUM>. The diaphragm <NUM> has a perimeter that overlaps the base <NUM> sufficiently to attach to the top surfaces of the side walls by one of the hermetic attachment methods available. Such means may include laser welding, frit bonding, anodic bonding, fusion bonding, or eutectic bonding, or other hermetic attachment method. The top surface <NUM> and the bottom surface <NUM> of the diaphragm <NUM> are shown as flat in the sketch, but these surfaces could have features etched or machined into them to facilitate fitting prior to attachment. Such features may include indentations, slots and ridges, holes and pegs, flanges, and the like. <FIG> illustrates a bonding technique that may be employed to attach the top wall <NUM>, which is also the diaphragm <NUM>, of the sensor <NUM>, to the side walls of the implant <NUM>. A first laser weld line 120A and a second laser weld line 120B may be employed to attach the side walls to the top wall. Each wall may include a double weld line about the perimeter of the side walls to ensure that the top wall <NUM> may be hermetically sealed to the side walls. <FIG> illustrates the first and second laser weld lines 120A, 120B between the top wall <NUM> and the side walls. Although two laser weld line are shown in this embodiment, other embodiments may use a single weld line, or any number of weld lines to affect the strength, stress, and hermetic properties of the weld.

The assembly or fabrication of electronics may occur in step <NUM> as illustrated by <FIG>. The implant <NUM> includes an antenna coil <NUM> that may be placed into the cavity <NUM> of the housing <NUM>. In one embodiment, the coil <NUM> is placed within the cavity via an opening in the bottom side of the housing <NUM> during assembly. Other electronic components, which may include one or more pressure sensors, may also be placed inside housing <NUM>. The electronic components may be placed at least partially inside the region defined by the coil <NUM>, or outside of this region. The electronic components may be positioned and attached along the inner surface <NUM> of the diaphragm <NUM>. The coil <NUM> may be positioned such that it surrounds the floating base <NUM> and the electronic components partially or fully. The electronics and coil <NUM> may be assembled and interconnected electrically prior to insertion into the housing <NUM>, or portions of the electronics and coil <NUM> may be inserted and then interconnected. By positioning the base <NUM> within the cavity <NUM> in a floating arrangement relative to the position of the coil <NUM>, it may reduce the overall size of the implant <NUM>. Additionally, during assembly, this configuration allows for accessibility to the electrodes without through vias or holes.

In the case where implant <NUM> contains a pressure sensor <NUM>, the internal electronic components may include one or more pressure sensors such as MEMS pressure sensor components and the top wall <NUM> may be a diaphragm such as a flexible membrane. The top wall <NUM> and electrodes 46A, 46B may communicate pressure by slight vibrations. Also, a gas, a fluid, or a gel may fill the cavity <NUM> formed by the housing <NUM>. In another embodiment, the bottom wall <NUM> may also be a diaphragm such as a flexible membrane which may include additional electrical components that may also be part of a sensing electronic circuit (not shown). In either embodiment, pressure measurements may be transduced directly into an electronic signal of a sensing circuit or component.

In other embodiments, sensor <NUM> may be a different type of sensor <NUM>, comprising only a single plate with at least two-coplanar electrodes and no base. Such a sensor can sense changes in the capacitance between the co-planar electrodes due to metal objects outside of the hermetic enclosure, or changes in capacitance due to chemical changes outside the enclosure. Coating the outside of the plate with a chemical that reacts with the environment in a desired way, to change capacitance can enhance this configuration.

The electronics may comprise one or more components <NUM>, <NUM>. The components <NUM>, <NUM> may serve as a trim element, to adjust the resonant frequency of the overall implant to a desired value for operation. The components <NUM>, <NUM> may be capacitive elements, inductive elements, or other electrical components. The components <NUM>, <NUM> may be resistive elements configured to adjust the Q factor of the implant <NUM>. They may be temperature sensitive elements configured to compensate for changes in temperature. They may be active circuits or integrated circuits. They may include modulating circuits, analog to digital conversion circuits, rectifiers, or other circuits. Additionally, a printed circuit board (PCB) <NUM> may be used to provide a mounting surface and electrical interconnection of the various electronic components <NUM>, <NUM>. The PCB <NUM> may be positioned on the floating base <NUM>. The PCB <NUM> may include electrical traces thereon to allow for electrical coupling to the coil <NUM>, electric components <NUM>, <NUM>, and may be electrically coupled to the electrodes 46A, 46B on the diaphragm <NUM> via wirebonds <NUM>. The PCB <NUM> may be any substrate that provides means for electrical connectivity between components. The PCB <NUM> substrate material may be plastic such as FR4, ceramic, glass, Rogers board, flex PCB, polyimide, silicon, quartz, paper, or other materials useful for this purpose. This allows for a variety of patterns wherein the connection between the coil <NUM>, the sensor <NUM>, and any other electronic components such as trim elements, may be accomplished through the PCB <NUM>. As illustrated by <FIG>, the coil <NUM> may be electrically connected to the PCB <NUM>. The coil <NUM> may be soldered to electric traces 94A, 94B positioned along the PCB <NUM>. Other electric connections, such as wedge bonding, ultrasonic welding, laser welding, or conductive adhesive, may also be utilized. The PCB <NUM> may be positioned within the perimeter of the coil <NUM>. In one embodiment, the PCB <NUM> may include electrical components such as a first capacitor <NUM> and a second capacitor <NUM> in electrical communication with the traces 94A, 94B and the coil <NUM>.

The coil <NUM> may be wound about center axis <NUM> as shown in <FIG>. The center axis may be generally parallel with the side walls <NUM>, <NUM>, <NUM>, and <NUM> and may be generally perpendicular to the top wall <NUM> and the bottom wall <NUM>. By orienting the top and bottom walls <NUM>, <NUM> such that they are generally perpendicular to the center axis <NUM> of coil <NUM>, this allows for more efficient assembly and use of space. In this way, the implant housing <NUM> may achieve the maximum cavity <NUM> area within the width constraint imposed on the short dimension. It will be appreciated that the coil axis <NUM> refers to the central axis of a generally spirally wound coil <NUM>, as shown in <FIG>. The spirally wound coil <NUM> may be any appropriate shape, such as circular, rectangular, or any other shape. The coil <NUM> may encircle the largest possible area within the cavity <NUM> of the implant <NUM>. The larger the area of the coil may provide a larger coupling coefficient for communication with an antenna of an external element. The external element, such as a reader, may provide power to the implant <NUM> and receive power or signals from the coil <NUM>. This inductive coupling between the coil <NUM> and the reader is disclosed by <CIT>. A larger coupling coefficient may provide more power to the implant <NUM> during energization, and may provide a stronger signal to the external reader unit when the implant <NUM> is transmitting or ringing back at a resonant frequency.

<FIG> shows the coil <NUM> extending vertically up to alignment with the PCB <NUM>. In another embodiment, the base <NUM> may be sized such that the coil <NUM> can wrap around the base <NUM> and PCB <NUM>, extending upwards in height until it spans the distance between the bottom surface <NUM> of the diaphragm <NUM> and the bottom wall <NUM> of the implant <NUM>. Increased coil <NUM> space allows for additional coil height which allows for additional coil turns. Coil <NUM> size may effect coil inductance, Q factor, coupling coefficient, and implant sensitivity. Coil <NUM> height can also be increased by increasing the thickness of the coil wire, which may also increase Q factor for the implant <NUM>.

The inner surface of the cavity <NUM> may be shaped to correspond to the shape of the coil <NUM> such that the coil <NUM> frictionally abuts against the inner surface of the side walls for a snug fit within the housing <NUM>. This configuration allows the coil <NUM> to surround the floating base <NUM> and may allow for a taller coil dimension within the cavity <NUM>. Alternatively, the side walls <NUM>, <NUM>, <NUM>, <NUM> may include an annular ridge or protrusion <NUM> (<FIG>) formed about at least a portion along the perimeter of the cavity <NUM> such that the coil <NUM> may be slightly deformed during assembly to overcome the annular ridge <NUM> to be retained within the cavity <NUM>. The annular ridge <NUM> may extend inwardly from the side walls <NUM>, and <NUM>. In yet another embodiment, coil <NUM> may be wound about a bobbin, made of plastic, ceramic, glass or a ferritic material. The bobbin may provide structure to the coil <NUM> to prevent false readings due to coil motion, to facilitate handling during assembly, or to change the coil's electrical properties.

<FIG> illustrates an embodiment of the housing <NUM> during assembly step <NUM> of <FIG>. Here the coil <NUM> and PCB <NUM> may be placed within the cavity <NUM> through the bottom opening. The PCB <NUM> may be attached to the floating base <NUM> of the sensor <NUM> and the coil <NUM> may be inserted within the side walls <NUM>, <NUM>, <NUM>, and <NUM>. The PCB <NUM> may be glued or otherwise attached to the floating base <NUM> on the underside of the top wall <NUM>. Referring to <FIG>, which is a view into the cavity <NUM> through the bottom of the partially assembled implant <NUM>, the bondpads 42A, 42B of the sensor <NUM> may be electrically attached to the PCB <NUM> by wirebonds <NUM>. The bondpads 42A, 42B may be laterally opposed such that the wirebonds <NUM> are attached to electrical traces 94A and 94B in electrical communication with the coil <NUM>, first capacitor <NUM>, and second capacitor <NUM>, as shown in <FIG>. In one embodiment, two wirebonds <NUM> may be made from each bondpad 42A, 42B to bondpads 93A, 93B at the end of each electrical trace 94A, 94B. Further, in one embodiment, the second capacitor <NUM> may be a capacitive temperature sensor provided on the PCB <NUM>. This second capacitor <NUM> may function to normalize capacitance related to temperature. As temperature increases, the capacitance may increase, which may counteract the effect of gas expansion, which may cause the capacitance of the sensor <NUM> to decrease. The second capacitor <NUM> may help reduce sensitivity to temperature changes.

In yet another embodiment, the PCB <NUM> may be eliminated as a separate component, and the interconnect pattern and pads may be deposited directly onto base <NUM>. In yet another embodiment, the walls <NUM>, <NUM>, <NUM>, or <NUM> of the housing <NUM> may have a flange that extends inwardly to support the PCB <NUM>. This arrangement may serve to reduce stress on the base <NUM>.

Step <NUM> of <FIG> describes connecting the sensor <NUM> to the assembly that includes the electronics and the coil <NUM>. It should be understood that the steps of <FIG> may be performed in a different sequence than that shown, depending on details of the implant <NUM> design, as well as process capabilities and priorities. In <FIG>, <FIG>, and <FIG>, the electrodes 46A, 46B of the sensor <NUM> are arranged in a series pattern otherwise referred to herein as the "serial capacitor" embodiment. In this embodiment, the top electrode 46A may include a plurality of electrodes 48A and 48B as illustrated by <FIG>. The bottom electrode 46B may be a single electrode. This electrode arrangement creates a first capacitor 46B-48A that is in series with a second capacitor 46B-48B. Electrodes 48A and 48B include bondpads 42A and 42B, respectively (as illustrated by <FIG>), and the bondpads 42A, 42B are accessible to make the electrical connection with the wirebonds <NUM> as illustrated by <FIG>.

In one embodiment, the series capacitance architecture may have a decreased overall capacitance compared to a parallel capacitance architecture. However, this configuration allows bondpads 42A and 42B to be accessible for electrical connection. In one embodiment, the electrodes 48A, 48B extend from the gap <NUM> through the vent <NUM> of the floating base <NUM> to bondpads 42A and 42B. The electrodes 48A, 48B may be placed near one another such that the wirebonds <NUM> are attached along only one side of the diaphragm <NUM>. This allows for a shorter interconnect which may provide for an improved manufacturing step and improved Q factor. The connection of the sensor <NUM> to the electronics may be accomplished by conventional wirebonding, soldering, ultrasonic bonding, wedge bonding, laser welding, conductive adhesives, or other means known to those in the art.

In step <NUM> of <FIG>, the bottom <NUM> may be attached to the housing <NUM>, completing the hermetic enclosure. The bottom wall <NUM> may cover the cavity <NUM> and abut against the bottom portion of side walls <NUM>, <NUM>, <NUM>, and <NUM> as illustrated by <FIG>. The bottom wall <NUM> may be attached to the side walls with a first laser weld line 122A and a second laser weld line 122B. Each wall may include a double weld line about the perimeter of the side walls to ensure that the bottom wall <NUM> may be hermetically sealed to the side walls, and to increase weld strength. Other embodiments may use single weld lines, partial weld lines, or multiple weld lines.

Further, scribe lines may be applied to the bottom wall <NUM>. <FIG> illustrates first and second scribe lines 124A, 124B on the bottom wall <NUM> in alignment with an outer perimeter of the side walls <NUM> and <NUM>. <FIG> illustrates second and third scribe lines 126A, 126B applied along the top wall <NUM> in alignment with an outer perimeter of the side walls <NUM> and <NUM>. The scribe lines allow excess pieces of the bottom wall <NUM> to be removed from the housing <NUM> to form the sensor implant <NUM> having a compact shape as illustrated by <FIG>.

The bottom wall <NUM> may be fabricated as a thin film with a thickness between about <NUM> - <NUM>, in one embodiment. The bottom wall <NUM> may be made from any material that can be attached to the housing <NUM>. Possible materials include, but are not limited to glass, quartz, sapphire, fused silica, alumina, titanium, and diamond.

Prior to step <NUM>, in some embodiments, additional items or materials may be placed within the cavity <NUM> to enhance implant <NUM> performance. Step <NUM> may take place in an air environment, or in another gas selected for its properties. Examples may include dry air or dry inert gas to reduce humidity inside the implant <NUM>. The bottom <NUM> may be attached in a vacuum, or a pressure other than ambient pressure. If the implant <NUM> is being used to sense pressure, a non-ambient internal pressure may be used to bias the implant towards a certain pressure, or to change the effects of internal gas expansion due to temperature change. The cavity <NUM> may be filled with a liquid or gel, used for example in a design where chip-scale pressure sensors reside on PCB <NUM>, and the liquid or gel transfers pressure from the diaphragm <NUM> to the chip scale pressure sensors. The cavity <NUM> may contain fluoroscopic ink, paint, contrast die, or other material or hardware designed to make the implant <NUM> visible under fluoroscopy. The cavity <NUM> may contain a getter or desiccant material to remove moisture, water or other undesired materials from other areas within cavity <NUM>. Desiccant may assist with controlling humidity or moisture within the cavity as moisture may cause the electrical components to drift or otherwise provide errors. Additionally, the desiccant may be adapted to change color when a change in humidity is detected and viewed through the transparent top and bottom walls. The cavity <NUM> may contain ferritic or other material to alter the properties of the coil <NUM> or other components. The cavity <NUM> may contain a gel, insert, or other material to alter the dielectric constant or other properties of the internal implant components. The cavity <NUM> may contain a bladder, whose stiffness is significantly lower than that of the pressure sensitive diaphragm <NUM>, which may compress more readily than diaphragm <NUM> when gas pressure inside the cavity <NUM> increases due to temperature change.

After the bottom <NUM> has been attached, the assembly of the implant <NUM> may, in some embodiments, proceed to step <NUM> of <FIG>. In this step, anchors <NUM> and <NUM> may be attached, and the body of the implant <NUM> may be coated with a material. A variety of anchor sizes, shapes, and attachment methods are possible. <FIG> illustrates the housing <NUM> with apertures <NUM>, <NUM> that extend through side walls <NUM>, <NUM> to receive the anchors <NUM>, <NUM>. The distal anchor <NUM> and the proximal anchor <NUM> may be inserted into the apertures <NUM>, <NUM>. Marker bands <NUM> may be attached to the ends of the anchors <NUM>, <NUM> within the apertures <NUM>, <NUM> to retain the anchors to the housing <NUM> and allow the anchors to extend from the top side <NUM> of the implant <NUM>. In one embodiment, the marker bands <NUM> may be made from radiopaque ink that may show up in various medical scans to identify the orientation of the implant <NUM> as it is positioned within the patient. The anchors may extend from the same side as the diaphragm <NUM>.

Once the anchors have been attached to the housing <NUM>, a coating may be applied to portions of the outer surface of the implant <NUM>. In one embodiment, the coating may be a silicone dip coating or dispersion coating. The thickness of the coating may be between about <NUM> to about <NUM>. A variety of other coatings may be considered, including parylene or other polymers. Coatings may be applied for their hydrophilic or hydrophobic properties, or to provide lubricity, mechanical strength, or fluoroscopic visibility. Coatings may be applied by dipping, spraying, vapor deposition, or other means in the art.

The implant <NUM> may meet the complex requirements of medical implants: (i) small cross-sectional area, (ii) non-metal housing, (iii) hermetic sealing, (iv) biocompatibility, and (v) maximum internal volume for a given external volume.

Any of the side walls <NUM>, <NUM>, <NUM>, <NUM>, bottom wall <NUM>, and diaphragm <NUM> may be generally transparent to allow one to view the components within the cavity <NUM> from outside the housing <NUM>. After the implant <NUM> has been assembled, it may be possible to adjust the functionality of the implant <NUM> to ensure that it may be compatible with a particular sensor reader. <FIG> illustrates that a laser beam <NUM> may be applied to the electric components through the top wall <NUM> to adjust the components in a desired manner. In particular, the first capacitor <NUM> may include a surface that may be affected by the laser beam. The capacitor <NUM> may be trimmable such that the laser may ablate part of an electrode on the surface of the first capacitor <NUM> to decrease the capacitance and change a property of the implant <NUM>, such as the resonant frequency. In one embodiment, the first capacitor <NUM> is adjusted to allow the implant sensor to transmit a signal in response to an excitation pulse at a desired frequency range. In one embodiment, that frequency range is between <NUM> to <NUM>, and more particularly between <NUM> to <NUM>, or between <NUM> to <NUM>, and preferably between <NUM> to <NUM>. Further, additional electronic adjustments may be made after assembly due to the transparent housing. Tracks on PCB <NUM> may be ablated by laser to add, remove, or reconfigure components within the circuitry. Notably, certain adhesives may be cured by the application of UV energy. MEMS electrodes may be trimmable, and resistors, ship inductors or other electrical components may be trimmable by the application of a laser beam through the housing. Sterilization of the components within the implant <NUM> may be accomplished through irradiation by gamma particles or other means. Other chemical or physical processes that can be affected or catalyzed by the application of light energy can also be carried out. An advantage to transparent or partially transparent sidewalls is that these adjustment steps may be carried out after the implant <NUM> has been hermetically sealed. These adjustments may be done in response to final measurements of the implant <NUM>, and not rendered invalid or inaccurate by later process steps.

In another embodiment, the PCB <NUM> may include indicia <NUM> printed thereon that may be viewed through the transparent top or bottom walls <NUM>, <NUM> for identification of the implant <NUM> as shown in <FIG>. Additionally, internal components may be inspected for damage or wear. Further, any of a number of visual indicator materials may be inspected: for example, a material in the cavity designed to change color in the presence of humidity would indicate that internal humidity has increased, possibly indicating a breach in the hermetic seal of the housing <NUM>.

It will be further appreciated that although the exemplary embodiments depict a rectangular coil, the coil <NUM> can be generally circular, ovular, rectangular, or can take the form of any polygon that encloses an area. Additionally, although a rectangular housing is shown in the exemplary embodiment figures, the concept of disposing the walls on the outer periphery of coil <NUM>, parallel to coil axis <NUM>, can be generalized to any polygonal shape. It will be further appreciated that the implant architecture can be used to maximize the size of any internal component, substance, or combination thereof. These may include, but are not limited to, drugs, steroids, batteries, stimulus electrodes, pacing circuitry, flow sensors, chemical sensors, or other electronics.

The disclosed invention may have a further benefit for pressure sensing implants. Many commonly available chip-scale pressure sensors are well suited for use in wireless implants. However, such pressure sensors generally have small, thin, pressure sensing diaphragms, on the order of <NUM> diameter or less and thickness of <NUM> or less. If such a diaphragm is exposed to living tissue or blood, one or more layers of cells will usually grow on it after a period of several days or weeks. Cell layers such as this are known to exhibit a stiffening effect to the sensor's or diaphragm, thereby decreasing the device's sensitivity. In the embodiment, shown in <FIG>, <FIG> and <FIG>, the top wall <NUM> (and in some embodiments, the bottom wall <NUM>) may serve as flexible pressure diaphragms, which communicate pressure to chip-scale pressure sensors on internal electronics through a pressure-communicating medium. In one embodiment, because the diaphragms of the instant implant are larger in area and generally stiffer than the diaphragms of known chip scale sensors, the top wall <NUM> will not be stiffened significantly by several layers of cell growth, compared to the smaller diaphragms of the chip-scale sensors. Thus the present invention allows pressure sensor implant designers to select from a number of available off-the-shelf or custom chip-scale pressure sensors, without having to worry about diaphragm stiffening due to cell growth.

The sensor implant housing <NUM> may be used with RF medical implants, the designs set forth herein are useful for any micro device or component where a non-metal hermetic enclosure is required and where it is desirable to maximize internal cavity space. Examples include, but are not limited to, sensors, actuators, or transponders located in harsh chemical environments, in liquid immersion, in high temperature zones (such as engines), or in environments where sterility is critical. Other examples include applications where the internal electronics must be hermetically housed, but cannot tolerate shielding or eddy current losses imposed by metal housings or braze rings. The designs and methods described herein overcome the many challenges associated with wireless sensors that use radiofrequency.

There are also numerous variations of the embodiment shown in <FIG>. For example, as shown in <FIG>, the housing <NUM> may be formed from a material having a single continuous construction wherein the top and bottom walls <NUM>, <NUM> may be attached. The cavity of the housing <NUM> maybe formed by one of the micromachining processes, chemical etching, conventional machining, or other type of machining known in the art. The cavity <NUM> may include the coil <NUM>, sensor <NUM>, and other internals inserted into the housing <NUM>. As shown in <FIG>, housing <NUM> may be formed with an integral base <NUM> that is continuous with the side walls of the housing <NUM> that includes a wirebond cavity <NUM> to allow attachment between the diaphragm <NUM> with the PCB <NUM> and coil <NUM>. The integral base <NUM> may include a top side and a bottom side wherein the top wall <NUM> may be adjacent to the top side of the integral base <NUM> and the bottom wall <NUM> may be adjacent to the integral base <NUM>. The diaphragm <NUM> and the bottom wall <NUM> may be laser welded <NUM> to the housing <NUM>.

<FIG> depict an embodiment in which the housing <NUM> may be formed with an integral base <NUM> that is continuous with the side walls of the housing <NUM> and includes at least one through substrate via (TSV) <NUM> to allow attachment between the sensor <NUM> on the top side of integral base <NUM> and the PCB <NUM> (<FIG>) and coil <NUM>. Alternatively, the sensor <NUM> may be connected to electronic traces patterned directly on the integral base <NUM> (<FIG>). The diaphragm <NUM> and bottom wall <NUM> may be laser welded <NUM> to the housing <NUM>. In these embodiments, use of the TSVs <NUM> may make the integral base <NUM> more robust and reduce assembly steps. Also, a capacitive gap <NUM> may be formed between the integral base <NUM> and the diaphragm <NUM>. Further, the embodiment of <FIG> does not require an attachment between the PCB <NUM> and base <NUM> as the electrical traces may be placed directly on the base for attachment to the coil, trimmable capacitors, and wirebonding.

In <FIG>, housing <NUM> may be made from a continuous material as in <FIG> but may include a deep bore for room to receive the sensor <NUM> as described above. The housing <NUM> includes a deep shelf <NUM> to support the PCB <NUM> thereon and is spaced to allow for attachment in a wirebond cavity <NUM>. Alternatively, deep shelf <NUM> may be implemented using a separate insert that is fixed to the housing walls by adhesives, press fit, fasteners, or welding. The top and bottom walls <NUM>, <NUM> are hermetically attached to housing <NUM> by laser weld <NUM> as before.

In <FIG>, housing <NUM> may be made from a continuous material as in <FIG> but includes a deep bore for room to receive the sensor <NUM> as described above. The housing <NUM> includes a deep shelf <NUM> to support the PCB <NUM> thereon and a space to allow for attachment in a wirebond cavity <NUM>. The housing <NUM> further includes through substrate vias (TSV) <NUM> to allow attachment between the sensor <NUM> on the top wall <NUM> with the PCB <NUM> and coil <NUM>. The top and bottom walls <NUM>, <NUM> are hermetically attached to housing <NUM> by laser weld <NUM> as before and a hermetic MEMS cavity <NUM> may be formed between the base <NUM> and the top wall <NUM>.

In <FIG>, housing <NUM> is made from a continuous material as in <FIG> but includes a coil cavity <NUM> to allow room for an enlarged coil <NUM> and to receive a top wall diaphragm <NUM> which is part of the sensor <NUM> with a floating base <NUM>. The coil <NUM> extends about the base <NUM>. The thick floating base <NUM> may be attached to the diaphragm <NUM> and include TSVs <NUM> as described above. The PCB <NUM> may be supported on the thick floating base <NUM> and be attached to TSVs <NUM> to allow attachment between the sensor <NUM>, the coil <NUM>, and other components. The top and bottom walls <NUM>, <NUM> are hermetically attached to housing <NUM> by laser weld <NUM> as before and a hermetic MEMS cavity <NUM> may be formed between the base <NUM> and the diaphragm <NUM>.

The invention disclosed herein is particularly advantageous when the wireless implant is required to be long and narrow, as is typically the case with cardiovascular implants. With such geometries, any coil width gained in the short dimension has a dramatic impact on coil area and hence link distance. In other embodiments, it may be advantageous to use the present invention to increase the height of a coil inside the implant.

<FIG> illustrates an alternativeversion for the implant <NUM>, yet not belonging to the invention. The sensor <NUM> may be fabricated as a unit as in previous embodiments, but in this case the base <NUM> is not "floating" wherein the base <NUM> may have a perimeter that extends passed portions of the perimeter of the diaphragm <NUM>. The base <NUM> may include a through hole <NUM> etched or machined into the base <NUM> such that bondwires <NUM> may extend to connect bondpads <NUM> on the sensor <NUM> to other bondpads on PCB <NUM>. Other components such as coil <NUM>, PCB <NUM>, and bottom <NUM> are attached as in previously described embodiments. This alternative embodiment may be somewhat taller overall than embodiments with a floating base, but it may bring about several advantages: (i) the thicker base <NUM> may make the sensor <NUM> more robust during handling and other operations during the assembly process; (ii) the weld <NUM> between the sensor <NUM> and housing <NUM> may induce less mechanical stress on the diaphragm <NUM>; (iii) the PCB <NUM> may induce less stress on the larger base <NUM>, and; (iv) the cavity <NUM> may have more volume for inclusion of other components described elsewhere.

<FIG> illustrates another version of the implant <NUM> not belonging to the invention. In this embodiment the sensor <NUM> is fabricated as a standalone unit as in previous embodiments but in this case the base <NUM> is not "floating" wherein the base <NUM> may have a perimeter that extends passed portions of the perimeter of the diaphragm <NUM>. The sensor <NUM> may be provided with one or more TSVs <NUM> (described elsewhere) in the base <NUM>, to electrically connect a base electrode <NUM> to a bondpad 996B located on the bottom side of base <NUM>. The sensor <NUM> features the large area base <NUM> and the small area diaphragm <NUM>, as well as the through hole <NUM> shown in the embodiment of <FIG>, and resides on top of housing <NUM>. The PCB <NUM> has bondpads which connect to bondpads 996A and 996B by wirebonds <NUM> and <NUM>, respectively. Alternatively, the PCB <NUM> may connect to bondpad 996B using a flipchip connection, such as ball bumping or stud bumping, or any other flipchip technology. This embodiment uses the TSVs <NUM> to connect directly to the base electrode <NUM> and the through hole <NUM> to connect directly to the diaphragm electrode <NUM>. This configuration enables a parallel capacitor arrangement, with one electrode <NUM> on the diaphragm <NUM> and one electrode <NUM> on the base <NUM>. This may be considered a "parallel capacitor" embodiment as distinct from the "serial capacitor" embodiment of <FIG>, <FIG>, and <FIG>, which includes two electrodes 48A and 48B along the diaphragm <NUM> and one electrode 46B along the base <NUM>. The parallel capacitor embodiment may provide twice the capacitance for the same electrode area and gap height as the serial capacitor embodiment which may provide an advantage in performance and design flexibility.

<FIG> illustrates another alternative embodiment of the implant <NUM>, which combines the concept of the TSV <NUM> from <FIG> with the floating base <NUM> concept of previous embodiments. Here, the implant <NUM> may include a parallel capacitor arrangement utilizing TSV <NUM>, as well as the reduced overall height provided by the floating base <NUM>.

<FIG> illustrates yet another embodiment of the implant <NUM>. As in <FIG>, it features TSV <NUM> and floating base <NUM>. However, the sensor <NUM> in <FIG> has a diaphragm <NUM> that is, in general, substantially thicker than the diaphragms in other floating base embodiments. The diaphragm <NUM> may have a thin region <NUM> machined over an area that is in alignment with the diaphragm electrode <NUM> and the base electrode <NUM> of the sensor <NUM>. The thin region <NUM> may be flexible as the surrounding thicker regions may provide increased mechanical strength that may bring about additional robustness during sensor <NUM> fabrication, handling, and implant <NUM> assembly. The increased thickness may also serve to isolate the flexible diaphragm region from stresses on the periphery of diaphragm <NUM>, or from the bond between diaphragm <NUM> and base <NUM>.

<FIG> is an alternative embodiment of the sensor <NUM>. As in other embodiments, the base <NUM> may include one or more TSVs <NUM>, <NUM> connecting a base electrode <NUM> to one or more bondpads 996A, 996B on opposite side of the base <NUM>. The base <NUM> may include one or more TSVs <NUM>, <NUM> that connect one or more electrodes <NUM>, <NUM> of the sensor <NUM> along or adjacent to the diaphragm <NUM> to one or more pads 996A, 996B on the opposite side of the base <NUM>. A cavity <NUM> may be formed between the base <NUM> and the diaphragm <NUM>. The top electrode <NUM> may electrically connect to the TSV <NUM> at pad <NUM> through the cavity <NUM>. The electrical connection may be made by thermo-compression bond, conductive epoxy, eutectic bond, solder reflow, or by capacitive coupling. Note that this multiple TSV concept could also be implemented in a sensor <NUM> embodiment that has the large base <NUM> feature as presented in <FIG>. In such an embodiment, the through hole <NUM> and wirebonds <NUM>, <NUM> in <FIG> would be replaced by the TSVs <NUM> and <NUM> from <FIG>.

<FIG> illustrates the sensor <NUM> embodiment of <FIG> incorporated into an implant <NUM>. This embodiment includes PCB <NUM> from earlier embodiments, but it may also use interconnect patterned directly on the base as described elsewhere.

It can readily be seen that key features from the various embodiments shown in <FIG> and <FIG> may be combined together in many other permutations, to achieve different design objectives. The figures are exemplary and intended to illustrate various design features.

Many of the embodiments disclosed herein may benefit from having the final sidewalls attached in a vacuum environment, to prevent internal pressures inside the housing from varying with temperature. Alternatively, the internal volume may be filled with an inert gas to limit corrosion of the internals. This may reduce the risk of problems related to moisture or other particulates.

It will also be appreciated that the implant housing embodiments disclosed herein can be made using all thick walls, and then post-processing the housing to thin portions of the walls that are parallel to the coil's axis. State of the art post-processing technologies such as grinding, polishing, etching, or laser ablation are some possible means for accomplishing this.

In one embodiment, the electrodes may be made of a metal, such as gold. In one embodiment, the TSVs may be made of an electrically conducting material, such as copper, nickel, titanium, or highly doped silicon.

It will be further appreciated that the embodiments of the invention described herein, as well as housing and wireless implant integration, may be performed at the die level or wafer scale, or some parts at wafer scale and some parts at die level.

The present invention describes several means of manufacturing an implantable wireless pressure sensor. Electronics may be inserted into the housing in a variety of locations and sequences. It should be appreciated that in other embodiments, the wireless sensor may incorporate sensitive biologic, chemical, optical, or other elements to allow for sensing of a variety of metrics.

In all embodiments, the external housing may be surface treated with a biocompatible material to limit clot formation, control cell growth, elute drugs, or improve lubricity. Such materials may include heparin, silicone, parylene, cell tissue monolayers, or other coatings well known to those of ordinary skill in the art. Other materials may be applied or coated onto the housing to improve overall shape for flow dynamics, improved deliverability, or other features. Additional mechanical features may be attached to the housing to facilitate implantation in a desired location in the body. Many such features are disclosed in PCT Patent Application No. PCT/<CIT> entitled Pressure Sensor, Centering Anchor, Delivery System and Method.

Claim 1:
An implant (<NUM>) comprising:
a housing (<NUM>, <NUM>, <NUM>, <NUM>) that defines a cavity (<NUM>);
a capacitive sensor (<NUM>) connected to said housing comprising:
a diaphragm (<NUM>, <NUM>) made of non-conductive material; and
a base attached to the diaphragm wherein said base is positioned entirely within said cavity,
wherein said base is a hanging base (<NUM>,<NUM>), wherein a first electrode (46A) is placed on said diaphragm (<NUM>,<NUM>) and a second electrode (46B) is placed on said hanging base (<NUM>,<NUM>), said hanging base (<NUM>,<NUM>) and said diaphragm (<NUM>,<NUM>) defining a capacitive gap (<NUM>),
characterized in that an attachment between the hanging base (<NUM>,<NUM>) and the diaphragm includes a discontinuity (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) that allows at least one electrical trace to connect at least one electrical contact (46A, 46B) outside of said capacitive gap to at least one electrode (46A, 46B, 48A, 48B) positioned at least partially within the capacitive gap..