# US 8,787,116 B2 · Collapsed mode operable cMUT including contoured substrate > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,787,116 B2 - Document ID: US8787116B2 - Status: Granted - Kind: B2 - Application number: 12/747,249 - Filed: 2008-12-12 - Published: 2011-02-17 - Granted: 2014-07-22 - Earliest claimed: 2007-12-14 - Assignees: Koninklijke Philips N.V. - Applicants: John Petruzzello; John Douglas Fraser; Shiwei Zhou; Benoit Dufort; Theodore James Letavic - Inventors: John Petruzzello; John Douglas Fraser; Shiwei Zhou; Benoit Dufort; Theodore James Letavic - Web page: https://patentgrep.com/patent/US8787116B2 ## CPC - B06B 1/0292: {Electrostatic transducers, e.g. electret-type} - B06B: METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, {e.g.} FOR PERFORMING MECHANICAL WORK IN GENERAL (for particular applications, see the relevant subclasses, e.g. B07B1/40, B23Q17/12, B24B31/06; measurement of mechanical vibrations G01H; in direction finding, locating, distance or velocity measuring G01S; {generating seismic energy G01V1/02}; control of mechanical vibrations in general G05D; sound-producing devices, e.g. bells, sirens, whistles G10K, {e.g. methods or devices for transmitting, conducting, or directing sound in general G10K11/00}; generation of electrical oscillations H03B; electromechanical resonators in general H03H; electromechanical transducers {for communication techniques, e.g. microphones, speakers} H04R) ## Abstract A capacitive ultrasound transducer capable of operation in collapsed mode either with a reduced bias voltage, or with no bias voltage, is provided. The transducer includes a substrate that is contoured so that a middle region of the flexible membrane is collapsed against the substrate in the absence of a bias voltage. A non-collapsible gap may exists between the substrate and peripheral regions of the flexible membrane. The contour of the substrate may be such as to strain the flexible membrane past the point of collapse, or to mechanically interfere with the flexible membrane. The substrate may include a further membrane disposed beneath the flexible membrane, the further membrane being contoured so that the flexible membrane is collapsed against it. The substrate may a support disposed beneath the further membrane to deflect a corresponding portion of the further membrane upward toward the flexible membrane. The support may be a post. The transducer may be operated in collapse mode with an improved efficiency (k2eff) as compared to otherwise similar conventional transducers exhibiting comparably uncontoured substrates. A related medical imaging system is provided, which may include an array of such transducers disposed on a common substrate. A method of operating such a transducer is provided that includes operating the transducer in the collapse mode in the absence of a bias voltage. ## Claims ### Claim 1 A capacitive ultrasound transducer, comprising: a substrate; and a flexible membrane, the flexible membrane including peripheral regions along which the flexible membrane is mounted to the substrate, and a middle region extending between the peripheral regions; wherein the substrate is contoured so that the flexible membrane is collapsed against the substrate in a vicinity of the middle region in the absence of a bias voltage, thereby permitting the transducer to be operated in collapse mode either with a reduced bias voltage, or with no bias voltage, wherein the substrate further includes a further membrane disposed beneath the flexible membrane, the further membrane being contoured so that the flexible membrane is collapsed against the further membrane in the vicinity of the middle region in the absence of a bias voltage, and wherein the substrate further includes a support disposed beneath the further membrane, the support being dimensioned and configured to deflect a corresponding portion of the further membrane upward toward the flexible membrane to an extent at least equal to the thickness of an original gap therebetween. ### Claim 2 (depends on 1) A capacitive ultrasound transducer in accordance with claim 1, wherein a non-collapsible gap exists between the substrate and the flexible membrane in a vicinity of the peripheral regions. ### Claim 3 (depends on 1) A capacitive ultrasound transducer in accordance with claim 1, wherein the substrate is contoured to strain the flexible membrane past the point of collapse in the vicinity of the middle region. ### Claim 4 (depends on 1) A capacitive ultrasound transducer in accordance with claim 1, wherein the substrate is contoured to mechanically interfere with the flexible membrane to an extent of up to about 2 μm in the vicinity of the middle region. ### Claim 5 (depends on 1) A capacitive ultrasound transducer in accordance with claim 1, wherein the substrate is contoured to mechanically interfere with the flexible membrane to an extent of about 1.6 μm in the vicinity of the middle region. ### Claim 6 (depends on 1) A capacitive ultrasound transducer in accordance with claim 1, wherein a length and thickness of the flexible membrane is greater than about 80 μm and less than about 3 μm, respectively, and the further membrane is at least about 4 μm thick. ### Claim 7 (depends on 1) A capacitive ultrasound transducer in accordance with claim 1, wherein a length and thickness of the membrane is about 100 μm and about 2 μm, respectively, and the further membrane is about 5 μm thick. ### Claim 8 (depends on 1) A capacitive ultrasound transducer in accordance with claim 1, wherein the support is a post disposed beneath the further membrane and vertically aligned with the middle region of the flexible membrane. ### Claim 9 (depends on 1) A capacitive ultrasound transducer in accordance with claim 1, wherein the support is structurally incomplete beneath regions of the further membrane other than a central portion thereof vertically aligned with the middle region of the flexible membrane. ### Claim 10 (depends on 1) A capacitive ultrasound transducer in accordance with claim 1, wherein the support operates to deflect a central portion of the further membrane vertically aligned with the middle region of the flexible membrane vertically upward to an extent of at least about 0.5 μm, while permitting at least one relatively peripheral portion of the further membrane to remain substantially vertically undeflected. ### Claim 11 (depends on 10) A capacitive ultrasound transducer in accordance with claim 10, wherein the support operates to deflect the central portion of the further membrane vertically upward to an extent of between about 0.9 μm and about 2.5 μm. ### Claim 12 (depends on 1) A capacitive ultrasound transducer in accordance with claim 1, wherein the substrate is contoured so that the flexible membrane is collapsed against the substrate in a vicinity of the middle region in the absence of a bias voltage, thereby permitting the transducer to be operated in collapse mode with an improved efficiency (k2eff) as compared to otherwise similar conventional transducers exhibiting comparably uncontoured substrates. ### Claim 13 (depends on 1) A medical imaging system comprising a capacitive ultrasound transducer in accordance with claim 1. ### Claim 14 (depends on 1) A medical imaging system comprising an array of capacitive ultrasound transducers in accordance with claim 1 disposed on a common substrate. ### Claim 15 A method of operating a capacitive ultrasound transducer, comprising: providing a transducer including a substrate and a flexible membrane, the flexible membrane including peripheral regions along which the flexible membrane is mounted to the substrate, and a middle region extending between the peripheral regions, wherein the substrate is contoured so that the flexible membrane is collapsed against the substrate in a vicinity of the middle region in the absence of a bias voltage; and operating the transducer in collapse mode in the absence of a bias voltage, wherein the substrate further includes a support disposed beneath a further membrane, the support being dimensioned and configured to deflect a corresponding portion of the further membrane upward toward the flexible membrane to an extent at least equal to the thickness of an original gap therebetween. ### Claim 16 (depends on 15) A method in accordance with claim 15, wherein the support includes a post disposed beneath the further membrane and vertically aligned with the middle region of the flexible membrane. ### Claim 17 (depends on 16) A method in accordance with claim 16, wherein the support is structurally incomplete beneath regions of the further membrane other than a central portion thereof vertically aligned with the middle region of the flexible membrane.