Scientists use phononic crystals to make dynamic acoustic tweezers

April 30, 2020

Acoustic tweezers are a powerful tool for contactless manipulation of particles and cells using acoustic radiation forces (ARF) generated by the transfer of acoustic wave momentum. They play an important role in display technology, biomedical sensors, imaging devices and diagnostic tools, etc.

Although standing waves or sound beams have been used in acoustic tweezer devices to trap particles, a huge phased array or a displacement platform is needed to shift the wave phase or move the sound source for dynamic manipulation requiring time-variant acoustic fields. Currently, it's still a challenge to achieve dynamic manipulation in a tiny microchannel with a simple, flexible, low-cost and disposable method.

A research team led by Prof. ZHENG Hairong from the Shenzhen Institutes of Advanced Technology (SIAT) of the Chinese Academy of Sciences has addressed the challenge of comprehensive, dynamic manipulation of particles and cells in a microchannel by integrating acoustofluidics, physics and fabrication of phononic crystals on the microscale.

In this study, a phononic crystal plate (PCP) fabricated by chemical etching and located in the microchannel created a tunable and time-variant sound field that generated a nonisotropic and reversible ARF that could be adjusted in real time.

The ARF originated from the interaction of the incident sound waves with the resonant excitation of two different modes in the phononic crystal plate.

These specific modes could be flexibly switched by simply changing the driving frequency. This change in frequency induced a highly localized acoustic field that generated a negative ARF to trap particles, along with a leaky field that caused a positive ARF to levitate particles, respectively.

In conjunction with an offset sound source setting for the PCP location, a radiation force induced by the field gradient along the channel could further transport levitated microparticles or cells toward the source along a certain predefined trajectory, such as a straight line, polyline line, arc line or loop line based on the straight line and arc line.

An arbitrary stop-and-go motion, namely, trapping and transportation, of particles and cells along a predefined path in the channel was achieved by switching the frequency so as to change the PCP' s resonant modes and by designing patterns on the phononic crystal plates in order to construct routes.

"By carefully designing and engineering acoustic fields using phononic crystals or metamaterials in microfluidic devices, a wide range of materials, particles, cells and organisms can be acoustically manipulated in a tunable and multifunctional manner for biomedical applications," said Prof. ZHENG.
-end-
The study was published as an Editors' suggestion in the journal Physical Review Applied on April 30. It has also been highlighted in , a free, online magazine from the American Physical Society featuring news and commentary about papers from the Physical Review that are of particularly broad interest.

Chinese Academy of Sciences Headquarters

Related Particles Articles from Brightsurf:

Comparing face coverings in controlling expired particles
Laboratory tests of surgical and N95 masks by researchers at UC Davis show that they do cut down the amount of aerosolized particles emitted during breathing, talking and coughing.

Big answers from tiny particles
A team of physicists led by Kanazawa University demonstrate a theoretical mechanism that would explain the tiny value for the mass of neutrinos and point out that key operators of the mechanism can be probed by current and future experiments.

How small particles could reshape Bennu and other asteroids
NASA's OSIRIS-REx spacecraft observed tiny bits of material jumping off the surface of the asteroid Bennu.

Probing the properties of magnetic quasi-particles
Researchers have for the first time measured a fundamental property of magnets called magnon polarisation -- and in the process, are making progress towards building low-energy devices.

TU Darmstadt: Pause button for light particles
Researchers at TU Darmstadt halt individual photons and can release them at the push of a button.

Chamber measurement standards established for fine particles
What effects do global warming and the formation of fine particles have on each other?

Distortion isn't a drag on fluid-straddling particles
New research published by EPJ E shows that the drag force experienced by fluid-straddling particles is less affected by interface distortion than previously believed.

Tiny 'bridges' help particles stick together
Understanding how particles bind together has implications for everything from the likelihood a riverbank will erode to the mechanism by which a drug works in the body.

Micromotors push around single cells and particles
A new type of micromotor -- powered by ultrasound and steered by magnets -- can move around individual cells and microscopic particles in crowded environments without damaging them.

Tiny particles lead to brighter clouds in the tropics
When clouds loft tropical air masses higher in the atmosphere, that air can carry up gases that form into tiny particles, starting a process that may end up brightening lower-level clouds, according to a CIRES-led study published today in Nature.

Read More: Particles News and Particles Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.