Implantable wireless pressure sensor

#Embodiments herein relate to implantable sensors and methods of manufacturing implanted sensors for wirelessly sensing pressure, temperature and other physical properties within the human body. More particularly, embodiments herein concerns a method of manufacturing a wireless, un-powered, micromachined pressure sensor that can be delivered using catheter-based endovascular or surgical techniques to a location within an organ or vessel. Embodiments are further directed in general to communicating with a wireless sensor, and in particular to communicating with a wireless sensor implanted within the body to measure a physical condition.

#The measurement of blood pressure within the human heart and its vasculature provides critical information regarding the organ's function. Many methods and techniques have been developed to give physicians the ability to monitor heart function to properly diagnose and treat various diseases and medical conditions. For example, a sensor placed within the chambers of the heart can be used to record variations in blood pressure based on physical changes to a mechanical element within the sensor. This information is then transferred through a wire from the sensor to an extracorporeal device that is capable of translating the data from the sensor into a measurable value that can be displayed. The drawback of this type of sensor is that there must be a wired connection between the sensor and the extracorporeal device, thus limiting Its use to acute settings.

#Many types of wireless sensors have been proposed that would allow implantation of the device into the body. Then, through the appropriate coupling means, pressure reading can be made over longer periods of interest. The primary limitation to these type of sensors is that the fabrication methods used to manufacture them do not provide sufficient miniaturization to allow them to be introduced and implanted into the heart using nonsurgical, catheter based techniques while maintaining the ability to communicate wirelessly with external electronics.

#FIG. 1 is a perspective view of a first embodiment of an implantable wireless sensor according to the present invention, with the sensor body shown as transparent to reveal interior detail.

#FIG. 2 is a schematic view of two pressure sensitive capacitor plates being formed in recessed trenches on two substrate wafers.

#FIG. 3 is a schematic view showing the wafers of FIG. 2 imposed in face-to-face relation.

#Referring now to the drawings, in which like numerals indicate like elements throughout the several views, FIG. 1 illustrates a sensor 10 for the measurement of physical parameters. The sensor can be fabricated using micro-machining techniques and is small, accurate, precise, durable, robust, biocompatible, and insensitive to changes in body chemistry, or biology. Additionally, the sensor can incorporate radiopaque features to enable fluoroscopic visualization during placement within the body. Furthermore, this sensor is encased in a hermetic, unitary package of electrically insulating material where the package is thinned in one region so as to deform under a physiologically relevant range of pressure. The LC circuit contained in the packaging is configured so that one electrode of the capacitor is formed on the thinned region. This sensor does not require the use of external connections to relay pressure information externally and does not need an internal power supply to perform its function. The pressure sensor of the current invention can be attached to the end of a catheter to be introduced into a human body and delivered to an organ or vessel using catheter-based endovascular techniques.

#Referring to FIG. 1, the sensor 10 includes a body 12. The body 12 is formed from electrically insulating materials, preferably biocompatible ceramics. In a preferred embodiment, the body is comprised of fused silica. The sensor 10 comprises a deflectable region 14 at the lower end of the body 12. The body 12 further comprises a lower chamber 19 and an upper chamber 21.

#An LC resonator is hermetically housed within the body 12 and comprises a capacitor 16 and an inductor 20. As used herein, the term “hermetic” will be understood to mean “completely sealed, especially against the escape or entry of air and bodily fluids.” The capacitor 15 is located within the lower cylindrical chamber 19 and comprises at least two plates 16, 18 disposed in parallel, spaced apart relation. The inductor 20 comprises a coil disposed within the upper chamber 21 and which is in conductive electrical contact with the capacitor 15.