CMUT Transducer Collapse Mode Lifetime Extension

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Solution Overview

Problem

Capacitive micro-machined ultrasound transducer (CMUT) cells operated in the collapse mode are prone to electric charging and dielectric breakdown, significantly reducing their lifetime due to prolonged contact with the substrate, which limits their sensitivity and operational lifespan.

Innovation Solution

Implementing a DC voltage control unit to disconnect the DC bias voltage during predefined time periods, temperature thresholds, or during imaging mode dead times to reduce the duration of the collapse mode, thereby limiting membrane contact with the substrate and preventing dielectric breakdown.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If CMUT cells are operated in the collapse mode with DC bias voltage to achieve high sensitivity, then the sensitivity of the transducer is improved, but the lifetime of the CMUT cells is significantly reduced due to electric charging and dielectric breakdown

Engineering Contradiction:

ImprovesensitivityVSAvoidlifetime

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies periodic action by switching the DC bias voltage on and off in a periodic manner. The DC voltage is applied only during the necessary measurement periods to maintain collapse mode for sensitivity, then switched off during dead times to allow the membrane to return to its relaxed state, preventing continuous contact and dielectric breakdown. This periodic switching enables the system to alternate between high-sensitivity collapse mode and protective non-collapse mode.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent implements preliminary action by switching off the DC bias voltage during predetermined dead times before dielectric breakdown can occur. The control system proactively manages the collapse mode duration, switching off the voltage during imaging mode dead times and storage periods to prevent wear-out from prolonged contact, rather than waiting for damage to occur.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If the DC bias voltage is continuously applied to maintain the collapse mode, then the sensitivity is maintained, but the membrane is in prolonged contact with the substrate causing dielectric breakdown

Engineering Contradiction:

ImprovesensitivityVSAvoiddielectric breakdown

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent converts the harmful effect of prolonged contact into a beneficial operational strategy by intentionally introducing dead times where the DC voltage is switched off. These dead times, which were previously wasted periods, are now utilized to protect the dielectric layer by allowing the membrane to separate from the substrate, transforming a previously harmful continuous operation into a protective periodic operation.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enhances the sensitivity of CMUT cells while significantly increasing their lifespan by reducing the time in the collapse mode, utilizing dead times for switching off the collapse mode during imaging scans and storage of image data, thus preventing wear-out from prolonged contact.

Implementation Method 1

a vibration of the flexible membrane, which move or vibrate according to the receiving ultrasound waves, can be detected by measuring a variation of the capacitance between electrodes of the flexible membrane and a substrate of the CMUT cells

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

a DC bias voltage is used to bring the membrane into contact with the CMUT substrate

Methodology Applied

Scientific EffectElectrostatic attraction: Electrostatics

Implementation Method 3

an electrical signal applied to the electrodes of the CMUT cells cause the membrane to vibrate and thereby to emit ultrasound waves

Methodology Applied

Scientific EffectElectrostatic attraction: Electrostatics

Data Source

PatentEP3052250B1Ultrasound transducer assembly and method for transmitting and receiving ultrasound waves

Publication Date: 2022.03.30 KONINKLIJKE PHILIPS NV

Figure 1
Figure 2a~2b
Figure 3a~3b

AI summary

An ultrasound transducer assembly (10) is disclosed comprising a plurality of transducer elements (32) for transmitting and receiving ultrasound waves (24) each having a substrate (40) and a flexible membrane (46) disposed in a distance from a substrate. An AC voltage control unit (56) is provided for controlling an AC voltage provided to each of the transducer elements, and a DC voltage control unit (60) for controlling a DC bias voltage provided to the transducer elements in order to bring the flexible membranes in a collapse mode into contact with the substrate. The DC voltage control unit is adapted to disconnect the DC bias voltage from the transducer elements temporarily during the operation of the ultrasound transducer assembly to limit the collapse mode.