Spatial ultrasound modulation by digitally controlling microbubble arrays

Abstract

Acoustic waves, capable of transmitting through optically opaque objects, have been widely used in biomedical imaging, industrial sensing and particle manipulation. High-fidelity wave front shaping is essential to further improve performance in these applications. An acoustic analog to the successful spatial light modulator (SLM) in optics would be highly desirable. To date there have been no techniques shown that provide effective and dynamic modulation of a sound wave and which also support scale-up to a high number of individually addressable pixels. In the present study, we introduce a dynamic spatial ultrasound modulator (SUM), which dynamically reshapes incident plane waves into complex acoustic images. Its transmission function is set with a digitally generated pattern of microbubbles controlled by a complementary metal–oxide–semiconductor (CMOS) chip, which results in a binary amplitude acoustic hologram. We employ this device to project sequentially changing acoustic images and demonstrate the first dynamic parallel assembly of microparticles using a SUM.

A Microfluidic Acoustic Metamaterial using Electrowetting: Enabling Active Broadband Tunability

“…Without any liquid droplet, the acoustic wave transmission from open slit and apertures has been investigated in literature for different slit aspect ratios and lower frequencies (<12 kHz). [32,33] However, when the water droplet covers the slit, the impedance mismatch of the liquidair interface affects the sound transmission, as shown recently by an air bubble based acoustic hologram in water [34] where electrolytic bubbles were used to create acoustic holograms because they can provide binary switching due to the impedance mismatch of air-water interface. The large impedance mismatch of air-water interface has also been used to modulate sound waves in superhydrophobic acoustic metasurface designs, where the Cassie-Baxter state of microstructured poly(vinylidene fluoride) membrane enabled confining of acoustic waves in an all-angle and wide spectrum range.…”

Three-Dimensional Trapping and Dynamic Axial Manipulation with Frequency-Tuned Spiraling Acoustical Tweezers: A Theoretical Study

“…Experimentally, some early demonstrations of particles trapping at the nodes and antinodes of standing waves depending on their properties were reported at the beginning of the twentieth century [10][11][12]. Since then, this principle has been refined, e.g., by combining highfrequency surface acoustic wave orthogonal transducers and microfluidics techniques to manipulate microparticles and cells in two dimensions in a microchannel [13,14], or by using static [15] or reconfigurable holograms [16][17][18][19][20] to pattern or manipulate many particles simultaneously in two and three dimensions. In acoustics, the term "acoustical tweezers" was introduced by Wu [21] in analogy with optical tweezers.…”

Bubble‐Induced In Situ Property Modulation of Liquid Metal

“…Due to the extreme fluidity and deformability of gas, the introduction of bubbles has been demonstrated to be a controllable real‐time technique for many applications, such as acoustic wave imaging. [ 18 ] Furthermore, bubbles between the interface of atomically thin films and substrates have been proved to be useful for exploring the local surface properties, such as adhesion energy [ 19 ] and strain engineering, [ 20 ] which attribute to the compression and expansion of bubble volume. Hence, the formation of bubbles at the liquid metal/oxide interface provides a favorable system to real‐time study and regulate novel interfacial properties of liquid metal at nanoscale.…”