Patent Issued for Piezoelectric Sensor, a Method for Manufacturing a Piezoelectric Sensor and a Medical Implantable Lead Comprising Such a Piezoelectric Sensor
Patent number 8626313 is assigned to St. Jude Medical, AB (Jarfalla, SE).
The following quote was obtained by the news editors from the background information supplied by the inventors: "The invention relates to a piezoelectric sensor having a layer of a piezoelectric material being applied to a supporting substrate.
"The invention also relates to a method for manufacturing of such a piezoelectric sensor.
"The invention also relates to a medical implantable lead comprising such a piezoelectric sensor.
"Piezoelectric sensors of the above type are commonly used to detect and measure physical characteristics, such as fluid pressure, stress in mechanical structures and the like. Briefly, piezoelectric sensors transform deformations into electrical signals or pulses. Accordingly, they have a wide applicability and are frequently used in industrial and electronic applications.
"A piezoelectric sensor of the above kind, may also be used in many different applications for monitoring various functions and organs inside a human or animal body. As such it may be used to monitor e.g. pressures inside tissue or body fluids. Hence, it can be used in for example a medical implantable lead connected to a pace maker to monitor blood pressure and/or heart rate inside a heart.
"U.S. Pat. No. 6,571,130 discloses a medical implantable lead comprising a piezoelectric sensor, which in one embodiment is formed in a distal and surface of the lead and in another embodiment is formed as a ring or envelope surface of the lead.
"Also, WO 02/34130 disclosed piezoelectric sensors for medical implantable leads, which are formed as tubes having the piezoelectric material applied on the outside of the supporting substrate or, on one embodiment, having the piezoelectric material formed as a self-supporting structure. On the outside, only a thin electrode layer is covering the outer surface of the piezoelectric sensor.
"However, in many cases it is disadvantageous to have the piezoelectric material in direct contact with tissue and/or body fluids, e.g. blood, since then the piezoelectric material should preferably be made of a biocompatible and non-toxic material, which might exclude the use of certain materials that could have better characteristics in certain aspects, either electrically and/or mechanically.
"Also the contacting of cables or coils to the electrodes can be problematic when in contact with body tissue or fluids since the connections, which normally are soldered or welded, will be more exposed."
In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "It is an object of the invention to provide an improved piezoelectric sensor. More precisely it is an object of the invention to provide a piezoelectric sensor in which the piezoelectric material and electric connections will be more shielded in relation to the environment.
"The invention also relates to a method for manufacturing of a piezoelectric sensor and a medical implantable lead comprising such a piezoelectric sensor, having essentially the same object as above.
"The invention is based on the insight that the above objects may be achieved by arranging the piezoelectric material on the inner circumference of a tubular supporting substrate. In this way the piezoelectric material and the electrical connections will be better protected against environmental influence and it is also possible to easily shield the piezoelectric material completely from the environment.
"Within this general idea, the invention can be realized in many different ways. Although preferred, it is not necessary that the piezoelectric sensor is cylindrical and formed with a circular cross section. On the contrary it is possible to have other cross sectional shapes as for example triangular, square, other polygonal shapes, oval or other arbitrary, regular or irregular shapes. The piezoelectric sensor could also be conical or truncated conical in longitudinal section. Accordingly, the term 'tubular' as used herein, is to be interpreted in an extensive way.
"Furthermore, the shielding against the environment of the piezoelectric sensor can be accomplished in many different ways. If, for example, the piezoelectric sensor is formed with a through bore, the sensor can be built into the structure of an object, e.g. a medical implantable lead in which it is going to be used, such that the piezoelectric material will be fluid tight shielded against environmental fluids, gases as well as liquids. Alternatively, the inner cavity of the sensor, in which the piezoelectric layer is positioned, can be fluid tight sealed in itself. Still another alternative is that the sensor is formed with an inner cavity, which is sealed but the sensor is provided with a through bore for allowing lead-through of for example electrical leads, torque transmitting wires, coils or the like. One advantage with having a fluid tight sealing of the inner cavity, in which the piezoelectric material is positioned, is that the sensitivity of the sensor will be increased. This is due to the fact that when the piezoelectric layer is in direct contact with fluids, the sensor is reacting on the direct fluid pressure on the piezoelectric material, whereas when sealed off inside a cavity, the piezoelectric layer will react to stresses in the supporting substrate due to deformations when the pressure outside the sensor varies.
"In a preferred embodiment, the supporting substrate also serves as the outer electrode for the piezoelectric sensor. In this way, the electrode can preferably be exposed to the environment, in e.g. a medical implantable lead, and used for the additional purpose of transmitting or receiving electrical signals to and from the environment, for example pacing signals to a heart in the case of a pacemaker lead. For this reason the supporting substrate can suitably be metallic, but it is also conceivable to use any other suitable, electrically conducting material, such as electrically conducting ceramics or plastics. However, it is within the scope of the invention, as is disclosed in a hereinafter described embodiment, that the supporting substrate can be electrically insulating, in which case a separate electrode is arranged between the piezoelectric material and the supporting substrate.
"Usually, the piezoelectric sensor comprises only one unitary piezoelectric layer, in which case only two electrodes, one on each side of the piezoelectric layer, and two connection leads is required. However, it is also possible to provide the sensor with a piezoelectric layer, which is separated into two or more different piezoelectric areas, each having a separate connection lead, which either can be operated separately or be connected in a suitably way to be operated in cooperation."
URL and more information on this patent, see: Eriksson, Tom; Nilsson, Kenth; Hedberg, Sven-Erik. Piezoelectric Sensor, a Method for Manufacturing a Piezoelectric Sensor and a Medical Implantable Lead Comprising Such a Piezoelectric Sensor. U.S. Patent Number 8626313, filed
Keywords for this news article include: St. Jude Medical AB.
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