Office of Technology Transfer – University of Michigan

Methods and Devices for Generating High-Amplitude and High-Frequency Focused Ultrasound With Light-Asorbing Materials

Technology #5233

Drawbacks Of Conventional Ultrasound Transducer Technology

Obtaining high-frequency ultrasound waves while maintaining strong pressure amplitudes at focal spots is a major challenge in the field of ultrasounic transducers.

Conventional ultrasound transducers such as those based on piezoelectric technologies are often used to generate high-amplitude waves. However, conventional transducers have low operation frequencies (<5 MHz), and large lens diameters, focal distances, and focal spot sizes. Such transducers cannot be used in applications that require high spatial resolutions—for example, at the level of an individual cell or single tissue layer.

Optoacoustic transducers are used to generate waves with high frequencies, but such transducers suffer from low output pressures. While wave pressure can be boosted externally by increasing the excitation laser energies, these energies are typically limited to prevent thermal damage to the optoacoustic sources.

University of Michigan’s High-Amplitude And High-Frequency Ultrasound Transducer Technology

Scientists at the Department of Electrical Engineering and Computer Science at the University of Michigan have developed a transducer technology that overcomes the above issues. The proposed technology, called laser-generated focused ultrasound (LGFU), can deliver optoacoustic pressures of over 100 MPa and 25 MPa on positive and negative peaks respectively, and over a 15 MHz frequency range.

LGFU utilizes multi-walled carbon nanotube (MW-CNT)-polymer composite films deposited uniformly on concave surfaces to generate strong optoacoustic pressures. LGFU is non- invasive and non-ionized, and has a clean bipolar waveform which can be controlled in a single pulse unit.

Applications

  • High-accuracy therapeutic transducers
  • High-frequency ultrasound generation
  • Diagnostic and therapeutic biomedical applications
  • Investigation of cell-ultrasound and membrane-bubble interactions in high resolution
  • Material and structural analysis using ultrasonic imaging
  • Thickness gauging of very thin material layers
  • Proximity/distance detection
  • Flow-rate sensing
  • Ultrasonic cleaning, welding, and testing
  • Fundamental understanding of nonlinear acoustics in high-frequency regimes

Advantages

  • Large wave pressures (over 100 MPa and 25 MPa on positive and negative peaks respectively)
  • High frequency (greater than 15 MHz frequency range) at focal point
  • Non-ionizing and non-invasive
  • Highly focused waves