Piezopolymer transducer with matching layer
Inventors
Vilkomerson, David • Chilipka, Thomas A
Assignees
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Publication Number
US-8564177-B2
Publication Date
2013-10-22
Expiration Date
Abstract
Matching layers improve the performance of ultrasonic transducers. Such layers have traditionally required significant effort and expense to be added to ultrasonic transducers. The present invention discloses a method of producing ultrasonic transducers with a matching layer, specifically for ultrasonic transducers utilizing piezopolymer transducer materials. Rather than the conventional method of forming the piezopolymer on a substrate and then attaching a matching layer through which the transducer emits its ultrasound energy, we teach depositing the piezopolymer on a substrate that also serves as a matching layer through which the ultrasound is emitted. Methods of how to select materials and modify their ultrasonic characteristics are also discussed.
Core Innovation
The invention relates to an ultrasonic transducer for use on a medium in which a piezopolymer layer having a first acoustic impedance is sandwiched between electrode layers to form a resulting structure. The resulting structure is disposed upon a substrate layer having a second acoustic impedance and is supported exclusively by the substrate layer. The substrate layer is configured for acoustically matching the structure to the medium.
The fabrication approach uses the substrate as the acoustic matching layer rather than attaching a separate matching layer after forming the piezopolymer transducer. Piezopolymer is deposited directly onto an acoustically tuned substrate or matching layer, and electrodes are patterned for poling and electrical operation as part of forming the electrode layers sandwiching the piezopolymer. This ties acoustic matching to the substrate impedance and the piezopolymer/electrode arrangement of the resulting structure.
Material selection and tuning are discussed in terms of acoustically matching by quarter-wavelength thickness, a target impedance, and adjusting effective impedance via electrode mass and thickness and piezopolymer thickness. The document also discusses tuning approaches including changing polyimide thickness, tuning metal type and thickness, varying piezopolymer thickness, and adding a reflective silver ink backing.
Claims Coverage
The independent claim provides core coverage for an ultrasonic transducer supported exclusively by an acoustically matching substrate layer, with a piezopolymer layer sandwiched between electrode layers. Dependent claims refine the piezopolymer composition, substrate material options, inclusion of a chrome adhesion layer, and the intended medium as human tissue.
Acoustically matched transducer with piezopolymer supported exclusively by substrate
An ultrasonic transducer for use on a medium comprising a piezopolymer layer sandwiched between electrode layers to form a resulting structure, wherein the resulting structure is disposed upon a substrate layer and supported exclusively by the substrate layer, and wherein the substrate layer is configured for acoustically matching the structure to the medium.
Piezopolymer as P(VDF75–TrFE25) copolymer
The transducer in which the piezopolymer layer comprises a P(VDF75–TrFE25) copolymer.
Substrate layer selected from PET, TPX, PEN, or polyimide
The transducer in which the substrate layer comprises one of the PET (Mylar), TPX, PEN, and polyimide material.
Chrome adhesion layer between electrode and substrate
The transducer further comprising a chrome adhesion layer disposed between an electrode layer and said substrate layer.
Medium is human tissue
The transducer according to claim 1 wherein the medium is human tissue.
Overall, the claim set is directed to a piezopolymer-based ultrasonic transducer in which the piezopolymer/electrode resulting structure is supported exclusively by an acoustically matching substrate, with dependent refinements specifying the P(VDF75–TrFE25) copolymer, particular substrate materials, a chrome adhesion layer, and operation on human tissue.
Stated Advantages
Increased sensitivity (reported as up to about 2.5× per volt).
Peak frequency shifts closer to about 30 MHz.
Documented Applications
Use of the ultrasonic transducer on a medium, including operation on human tissue.
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