# US 10,770,058 B2 · Acoustic lens for micromachined ultrasound transducers

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- Number: US 10,770,058 B2
- Document ID: US10770058B2
- Status: Granted
- Kind: B2
- Application number: 15/995,015
- Filed: 2018-05-31
- Published: 2018-10-04
- Granted: 2020-09-08
- Earliest claimed: 2013-03-15
- Assignees: Fujifilm Sonosite, Inc.
- Applicants: FUJIFILM SonoSite, Inc.
- Inventors: Wei Li; Paul Dunham; Chak-Yoon Aw; N. Chris Chaggares
- Web page: https://patentgrep.com/patent/US10770058B2

## CPC

- G10K 11/30: using refraction, e.g. acoustic lenses
- B06B 1/0292: {Electrostatic transducers, e.g. electret-type}
- B06B 1/0611: {in a pile}
- B81B 3/0021: {Transducers for transforming electrical into mechanical energy or vice versa (dynamo-electric machines H02K99/00; electrostatic machines H02N1/00; piezoelectric devices H10N30/00)}
- G01N 29/06: Visualisation of the interior, e.g. acoustic microscopy {(medical or veterinary diagnosis using sonic waves A61B8/00; representation of acoustic wave distribution G01H3/125, G01H9/002; short-range imaging systems using reflection of acoustic waves G01S15/8906)}
- G01N 29/221: {Arrangements for directing or focusing the acoustical waves (electronic orientation or focusing G01N29/262; sound directing or focusing G10K11/26; mechanical steering of sound transducers or their beams G10K11/35)}
- G01N 29/2406: {Electrostatic or capacitive probes, e.g. electret or cMUT-probes}
- G01N 29/2437: {Piezoelectric probes}
- G01N 29/28: providing acoustic coupling {, e.g. water (impedance matching G10K11/02)}
- G10K 11/168: Plural layers of different materials, e.g. sandwiches
- H10N 30/101: {with electrical and mechanical input and output, e.g. having combined actuator and sensor parts}
- B81B 2201/02: Sensors
- G10K: SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- 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)
- B81B: MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES (piezoelectric, electrostrictive or magnetostrictive elements per se H10N30/00, H10N35/00)
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR

## Abstract

Matching layers configured for use with ultrasound transducers are disclosed herein. In one embodiment, a transducer stack can include a capacitive micromachined ultrasound transducer (CMUT), an acoustic lens, and a matching layer therebetween. The matching layer can be made from a compliant material (e.g. an elastomer and/or an liquid) and configured for use with CMUTs. The matching layer can include a bottom surface overlying a top surface of the transducer and a top surface underlying a bottom surface of the lens.

## Claims

### Claim 1

An ultrasonic transducer stack comprising:
a first matching layer having a first top surface and a first bottom surface, wherein the first matching layer comprises a compliant material, and wherein the first matching layer has a first thickness and a first acoustic impedance;
a lens layer having a second bottom surface comprising a polymethylpentene or a thermoset cross-linked styrene copolymer material that is textured overlying the first top surface, and a second top surface, wherein the lens layer has a second thickness and a second acoustic impedance; and
a transducer layer having a third top surface underlying the first bottom surface and the second bottom surface, wherein the transducer layer includes a micromachined ultrasound transducer configured to generate ultrasound at a center frequency, and wherein the third top surface comprises an upper membrane of the transducer.

### Claim 2 (depends on 1)

The transducer stack of claim 1 wherein the compliant material comprises a PDMS-type silicone.

### Claim 3 (depends on 1)

The transducer stack of claim 1 wherein the compliant material has a Young's Modulus of less than 100 MPa.

### Claim 4 (depends on 1)

The transducer stack of claim 1 wherein the first thickness is less than the second thickness.

### Claim 5 (depends on 1)

The transducer stack of claim 1 wherein the first thickness is less than ¼ wavelength of the center frequency.

### Claim 6 (depends on 1)

The transducer stack of claim 1 wherein the center frequency is greater than 15 MHz.

### Claim 7 (depends on 1)

The transducer stack of claim 1 wherein the second bottom surface is textured with a plurality of ridges and a plurality of grooves therebetween.

### Claim 8 (depends on 1)

The transducer stack of claim 1 wherein the compliant layer comprises a matrix material, and wherein the first matching layer comprises a composite layer made of a first plurality of micron-sized particles and a second plurality of nano-sized particles combines with the matrix material.

### Claim 9 (depends on 1)

The transducer stack of claim 1 wherein the first plurality of micron-sized particles are selected based on a desired acoustic impedance of the composite material.

### Claim 10 (depends on 1)

The transducer stack of claim 1, further comprising a second matching layer disposed between the first matching layer and the lens layer.

### Claim 11

An ultrasound transducer stack for external use, the ultrasound transducer stack comprising:
a first matching layer having a first top surface and a first bottom surface, wherein the first matching layer includes a first compliant material and wherein the first matching layer has a first acoustic impedance;
a lens layer having a second bottom surface comprising a polymethylpentene or a thermoset cross-linked styrene copolymer material that is textured with a plurality of ridges and a plurality grooves therebetween overlying the first top surface and a second top configured to be placed against a subject's skin, wherein the lens layer has a second acoustic impedance different from the first acoustic impedance; and
a third layer having a third top surface underlying the first bottom surface and the second bottom surface, wherein the third layer includes a micromachines ultrasound transducer configured to generate ultrasound.

### Claim 12 (depends on 11)

The transducer stack of claim 11 wherein the compliant material is a PDMS-type silicone.

### Claim 13 (depends on 11)

The transducer stack of claim 11 wherein the complaint material includes water.

### Claim 14 (depends on 11)

The transducer stack of claim 11 wherein the third top surface comprises an anti-corrosive material.

### Claim 15 (depends on 11)

The transducer stack of claim 11 wherein the lens layer is removably attached to the first matching layer.

### Claim 16 (depends on 11)

The transducer stack of claim 11 wherein the first matching layer includes a first plurality of micron-sized and second plurality of nano-sized particles combined with the compliant material to form a composite material.

### Claim 17 (depends on 11)

The transducer stack of claim 11 wherein the compliant material includes a fluid.

### Claim 18 (depends on 11)

The transducer stack of claim 11 wherein the micromachines ultrasound transducer is a CMUT.

### Claim 19 (depends on 11)

The transducer stack of claim 11 wherein the micromachined ultrasound transducer is a PMUT.