Acoustically trapped colloidal crystals that are reconfigurable in real time

Area of Science:

• Metamaterials science
• Acoustic physics
• Colloidal science

Background:

• Photonic and phononic crystals are metamaterials with repeating structures.
• These materials exhibit unique wave guiding and filtering properties.
• Current applications include hyperlenses and superabsorbers.

Purpose of the Study:

• To demonstrate the first reconfigurable 3D colloidal phononic crystal.
• To show real-time alteration of frequency filtering characteristics.
• To explore the use of acoustic radiation forces for material assembly.

Main Methods:

• Assembled microspheres in aqueous solution using acoustic radiation forces.
• Created a colloidal crystal with spheres arranged in an orthorhombic lattice.
• Controlled lattice spacing using acoustic wavelength.

Main Results:

• Demonstrated a 3D colloidal phononic crystal reconfigurable in real time.
• Observed rapid alteration of frequency filtering properties.
• Transmission acoustic spectroscopy confirmed metamaterial behavior with tunable band-pass and band-stop frequencies.

Conclusions:

• The developed material represents a novel reconfigurable phononic metamaterial.
• Acoustic radiation forces enable real-time control over crystal structure and filtering.
• This technology opens new avenues for tunable acoustic devices.