Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Optical generation of ultrasound via photoacoustic effect

01.03.2017

A group of University College London researchers have used tailored optoacoustic surface profiles to generate acoustic fields focused at multiple points using a single optical pulse

Limitations of the piezoelectric array technologies conventionally used for ultrasonics inspired a group of University College London researchers to explore an alternative mechanism for generating ultrasound via light, also known as the photoacoustic effect. Coupling this with 3-D printing, the group was able to generate sounds fields with specific shapes for potential use in biological cell manipulation and drug delivery.


This is a fabricated sample before absorber deposition.

Credit: Brown et al.

Piezoelectric materials generate mechanical stress in response to an applied electric field, resulting in a usable and precisely controllable force that can, for example, be used to create sound waves. But achieving this control with conventional piezoelectric arrays requires both complicated electronics and large numbers of extremely small individual components which are expensive and difficult to manufacture.

The photoacoustic effect, in contrast, occurs when a short pulse or modulated source of light is absorbed by a material, producing a sound wave. As the group reports in this week's Applied Physics Letters, from AIP Publishing, their work focuses on using the photoacoustic effect to control ultrasound fields in 3-D.

"One useful feature of the photoacoustic effect is that the initial shape of the sound that's generated is determined [by] where the light is absorbed," said Michael Brown, a doctoral student at the Biomedical Ultrasound Group of the Department of Medical Physics and Biomedical Engineering at University College London. "This can be used to create tightly focused intense points of sound just by depositing an optical absorber on a concave surface, which acts like a lens."

More generally, it's possible to manufacture samples with nearly any surface shape by using a 3-D printer and a transparent material.

"By depositing an optical absorber on this surface, which can be done via spray painting, a sound wave of nearly any shape can be created by illuminating this sample with a laser," Brown said. "If you carefully tailor the design of the surface and therefore the shape of the acoustic wave, it's possible to control where the sound field will focus and even create fields focused over continuous shapes. We're using letters and numbers."

This is particularly significant because, in theory, the ability to control the shape of the wavefront -- the surface over which the sound wave has a constant phase, somewhat like the edge of the wave -- enables a large degree of control over the resulting field.

"But actually designing a wavefront that generates a desired pattern becomes more challenging as the complexity of the target increases," Brown said. "A clear 'best' design is only available for a few select cases, such as the generation of a single focus."

To overcome this limitation, the group "developed an algorithm that allows users to input a desired sound field in 3-D, and it then outputs a 3-D printable surface profile that generates this field," Brown said. "Our algorithm allows for precise control of the intensity of sound at different locations and the time at which the sound arrives, making it quick and easy to design surfaces or 'lenses' for a desired application."

Brown and his colleagues demonstrated the effectiveness of their algorithm by creating a lens designed to generate a sound field shaped like the numeral 7. After illuminating the lens by a pulsed laser, they recorded the sound field and the desired "7" was clearly visible with high contrast.

"It was the first demonstration of generating a multi-focal distribution of sound using this approach," Brown said.

There are many potential uses for the tailored optoacoustic profiles created by the group. "Highly intense sound can cause heating or exert forces on objects, such as in acoustic tweezers," Brown said. "And similar single-focus devices are already being used for cleaving cell clusters and targeted drug delivery, so our work could be useful within that area."

The group is also interested in the effects of propagating through tissue, which introduces distortions to the shape of wavefronts caused by variations in the speed of sound. "If the structure of the tissue is known beforehand via imaging, our approach can be used to correct for these aberrations," Brown said. "Manipulating the shape and time during which the focused sound is generated can also be useful for the maneuvering and controlling biological cells and other particles."

Going forward, Brown and his group hope to investigate the use of other light sources and what advantages they might offer.

"One limitation of our work was the use of a single-pulsed laser," Brown said. "This meant that the temporal shape of the sound generated from the sample was only one short pulse, which limited the complexity of the fields that could be generated. In the future, we're interested in using alternative modulated optical sources to illuminate these devices."

###

The article, "Generating arbitrary ultrasound fields with tailored optoacoustic surface profiles," is authored by Michael Brown, Daniil Nikitichev, Bradley E. Treeby and Ben Cox. The article will appear in the journal Applied Physics Letters Feb. 28, 2017 (DOI: 10.1063/1.4976942). After that date, it can be accessed at http://aip.scitation.org/doi/full/10.1063/1.4976942.

ABOUT THE JOURNAL

Applied Physics Letters features concise, rapid reports on significant new findings in applied physics. The journal covers new experimental and theoretical research on applications of physics phenomena related to all branches of science, engineering, and modern technology. See http://apl.aip.org.

Media Contact

AIP Media Line
media@aip.org
301-209-3090

 @jasonbardi

http://www.aip.org 

AIP Media Line | EurekAlert!

Further reports about: Applied Physics Letters Optical piezoelectric sound wave

More articles from Physics and Astronomy:

nachricht A two-atom quantum duet
12.11.2018 | Institute for Basic Science

nachricht Improving understanding of how the Solar System is formed
12.11.2018 | Goethe-Universität Frankfurt am Main

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

Im Focus: Coping with errors in the quantum age

Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly

The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...

Im Focus: Nanorobots propel through the eye

Scientists developed specially coated nanometer-sized vehicles that can be actively moved through dense tissue like the vitreous of the eye. So far, the transport of nano-vehicles has only been demonstrated in model systems or biological fluids, but not in real tissue. The work was published in the journal Science Advances and constitutes one step further towards nanorobots becoming minimally-invasive tools for precisely delivering medicine to where it is needed.

Researchers of the “Micro, Nano and Molecular Systems” Lab at the Max Planck Institute for Intelligent Systems in Stuttgart, together with an international...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

In focus: Peptides, the “little brothers and sisters” of proteins

12.11.2018 | Life Sciences

Materials scientist creates fabric alternative to batteries for wearable devices

12.11.2018 | Materials Sciences

A two-atom quantum duet

12.11.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>