Transducer Engineering

The acoustic transducer of an ultrasound measurement system converts the electrical signals from the system into the acoustic wave and vice versa. The acoustic wave is used to collect the desired information from the medium or body (e. g., the distance to an object or changes in tissue or in materials). It is the front end of the measurement system in contact to the object or media of interest and with this an important, performance-determining part of the measurement chain. As it is in direct contact with the measurement object or the medium, it is also exposed to the environmental conditions at the measurement location and, as well as the necessary acoustic properties, also has to fulfil all of the requirements in terms of pressure, temperature, resistance to media, vibrations or shock. In addition to this, there are requirements in terms of space, design or appearance. Such a wide range of special requirements can generally only be fulfilled with an application-specific product development.

This is why we offer services for the new development or optimization of specialized sensors or actuators. This includes, for example, the specification and design of transducer systems, prototype construction, electric and acoustic validation as well as load and endurance tests. Our developments are already on the market in a wide range of products in the fields of medicine, industry or sonar applications. The frequency range in which we offer solutions knows almost no limits. It begins at low frequency at 20 kHz for cleaning or sonar applications, and ends at very high frequency at 1 GHz with sensors for applications in ultrasound microscopes. Other examples for possible sensors include:

  • medical phased, linear or curved arrays
  • matrix arrays for volumetric diagnostics
  • therapeutic and combined diagnostic/therapeutic sensors
  • catheter-based single-element transducers and arrays
  • sensors for flow measurement in gases and fluids (e. g. also clamp-on)
  • level or distance sensors (e. g. level metering in a tank, parking assistance)
  • echosounders, sidescan sonar systems
  • volumetric sonar sensors (based on Mills-Cross technology or full-matrix arrays)
  • special solutions for sonar-based object recognition (active/passive)

We work in close cooperation with the other development groups of the main department of Ultrasound and offer the entire development process from the idea to the product. Thanks to our long years of experience, our effective processes and excellent technical equipment, we can realize lean developments with short time-to-market.

Medical Sensors

© Fraunhofer IBMT.

High frequency linear array for imaging.

Ultrasound technology is well established in the medical sector for diagnostic and therapeutic applications.

Ultrasound imaging is the common application, but blood flow measurement, diagnosis of osteoporosis or the assistance of healing processes by the application of ultrasound are also important applications in medicine.

We offer development services and production technologies for medical sensors with frequencies up to 50 MHz. For example:

  • Linear and phased arrays for imaging
  • Two-dimensional arrays
  • Doppler sonography
  • Catheter-based or intravascular probes
  • Therapeutic applicators
  • Miniaturized Piezosystems (e. g. hearing aid)

Industrial Sensors

© Fraunhofer IBMT.

Phased array for air and measured image.

Ultrasound sensors are used in many industrial measurement applications. The best interaction between sensor, measuring medium and object under given environmental conditions (pressure, temperature, medium) is the basis for a high-quality and safe signal analysis.

We offer development services and production technologies up to 50 MHz for all types of media on the following fields:

  • Level measurement
  • Flow measurement
  • Process control (e. g. concentration)
  • Geometry measurement
  • Object detection
  • Measurement of layer thickness

Air Transducers

© Fraunhofer IBMT.

Ultrasound airborne transducer.

Ultrasound transducers for soft sound propagation media like air are required for distance measuring, for flow metering of gases or the characterization of surfaces. The transmission characteristics should be both sensitive and broadband at acceptable costs. This often canonly be achieved by an application-specific development.

The working group Transducer Development provides market and feasibility studies as well as development capacity for such transducers and takes care of your problem solution right up to production. The upper frequency for these applications is in the range of 2 MHz.

Immersion & Contact Transducers

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Ultrasound immersion and contact transducers.

Immersion and contact transducers form a special group of industrial sensors because they have contact with the medium and/or the object. his means that they are exposed to the environmental conditions (e. g. pressure, temperature). But they also need to have special characteristics such as medium stability and abrasion resistance in the industrial environment.

We offer development services and production technologies for sensors up to 50 MHz in the following fields:

  • Level measurement technology
  • Flow measurement technology
  • Process control
  • Geometry measurement
  • Quality control (e. g. material properties)

Underwater Sensors

© Fraunhofer IBMT.

Sidescan Sonar System.

Underwater applications of ultrasound form a very large group with a long history. Important examples are:

  • Fish finding
  • Census of marine life
  • Object detection and identification
  • Collision avoidance
  • Bottom profiling
  • Sub-bottom profiling
  • Underwater communication
  • Navigation assistance

We offer development services and production technologies for the fields mentioned above and the following devices:

  • Echosounders
  • Sidescan sonar systems
  • Linear or Phased arrays
  • 2D-Arrays
  • Doppler sensors
  • Communication modules

High-Power Ultrasonic Tranducers

© Fraunhofer IBMT.

Ultrasound power transducers.

Applications of ultrasound in which high-acoustic intensity is inserted in a medium are called “high-power applications”. For example:

  • Cleaning
  • Welding
  • Dispersing
  • Disagglomeration
  • Destruction of germs, tissue or objects

We offer development services and production technologies for high-efficiency oscillation systems for the following devices:

  • Sonotrodes (for ultrasonic welding, dispersion, dental technology etc.)
  • Tonpilz resonators for low-frequency cleaning
  • Megasound cleaning systems
  • Ultrasonic applicators for medical applications (e. g. therapy devices, ultrasonic lithotripsy)

High-Frequency Ultrasound Transducers

© Fraunhofer IBMT.

High frequency ultrasound lenses.

Focusing ultrasound lenses and non-focusing ultrasound transducers in the frequency range between 100 MHz and 1 GHz are mostly applied in non-destructive testing and in biomedical research. The small wavelengths at high frequencies allow an increase of the spatial resolution. If high-frequency sound waves are additionally focused by a lens, focus diameters in the range of a few micrometers become possible.

High-Frequency Ultrasound Arrays

© Fraunhofer IBMT.

100 MHz ultrasound array.

High-frequency ultrasound arrays can be applied in non-destructive testing and in medical science. Compared with single element ultrasound transducers, they offer the advantage of electronic beam forming and scanning. A bandwidth of 100 MHz is offered by the 128 channel electronics of the working group Ultrasound Systems/Clinical Applications. An increase in the frequency beyond 100 MHz is not useful for medical applications, because the penetration depth of sound in tissue is only 2 mm at this frequency. Typical medical applications are in the frequency range up to 50 MHz.

Passive Elements for High-Frequency Ultrasound

© Fraunhofer IBMT.

16 x 16 circular piezoelectric layers with gold electrodes on a silicon wafer.

Acoustic matching layers for high-frequency ultrasound have special requirements. They have to match the acoustic impedance of an ultrasound transducer to the acoustic impedance of the examined media, thus enabling a maximum transmission, and at the same time have a low attenuation. These requirements are satisfied by nano-doped acoustic matching layers. The acoustic impedance can be adjusted in the range between 4 and 7 MRayl by the content of nanoparticles. This range allows optimized matching layers for the interface between piezoceramics and water or biological tissue. An attenuation by scattering does not take place, because even at 1 GHz the dispersed nanoparticles are much smaller than the wavelength of ultrasound.

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