Publisher’s Note: “Multifunctional acoustic holography based on compact acoustic geometric-phase meta-array” [J. Appl. Phys. 131, 185108 (2022)]

Acoustic Trapping: An Emerging Tool for Microfabrication Technology

“…To generate such nonsymmetrical acoustic pressure fields generally requires more complex devices using complicated arrangements of transducers or structures such as acoustic holograms, which give rise to a wide range of patterns, including Bessel-function acoustic pressure fields [40,74,75,77,[85][86][87][88] or arbitrary patterns. [41,[89][90][91][92][93][94][95] To this end, different types of acoustic trapping devices with more transducer elements, such as 1D, 2D, [40,77] or circularly arranged [74,75,[85][86][87] ultrasound transducer arrays, have been developed. The additional modulation of the frequency, phase, amplitude, and pulse duration of the individual elements of the ultrasound transducer can be used to deposit microparticles in an arbitrary acoustic pressure field to generate nonsymmetrical patterns.…”

“…An alternative approach to generating arbitrary fields with a single transducer, is to project the sound through a structured plate, known as an acoustic hologram. [41,[89][90][91][92][93][94][95] For instance, Melde et al [90] demonstrated an elegant approach to deposit microparticles into an arbitrary 2D patterns using only one transducer in combination with a 3D-printed acoustic hologram which was a plate with a varying thickness. The acoustic wave passes through the acoustic hologram into the trapping chamber, where the pressure amplitude and phase are determined by the acoustic hologram, and used for the immobilization of microparticles (Figure 5A-C) and cells (Figure 5D,E).…”

“…An alternative approach to generating arbitrary fields with a single transducer, is to project the sound through a structured plate, known as an acoustic hologram. [ 41,89–95 ] For instance, Melde et al. [ 90 ] demonstrated an elegant approach to deposit microparticles into an arbitrary 2D patterns using only one transducer in combination with a 3D‐printed acoustic hologram which was a plate with a varying thickness.…”

Programmable Acoustic Holography using Medium‐Sound‐Speed Modulation

“…A limitation of most static metasurface-based holograms [29,38,39] is that only a single and static acoustic field can be generated at a target plane for a given hologram, limiting the range of activities that can be performed, whereas applications in tissue engineering and 3D printing benefit from the incorporation of designed heterogeneity. [40,41] Flexible and reconfigurable acoustic fields can be generated using phased array transducers (PATs), [17,[42][43][44][45][46] in which many ultrasonic devices are individually actuated with varying phase/amplitude. However, the aperture size and drive circuitry of PATs add cost and complexity as the element number increases, [47,48] limiting the spatial resolution at which PATs can create sophisticated wavefront manipulation.…”

“…Flexible and reconfigurable acoustic fields can be generated using phased array transducers (PATs), [ 17 , 42 , 43 , 44 , 45 , 46 ] in which many ultrasonic devices are individually actuated with varying phase/amplitude. However, the aperture size and drive circuitry of PATs add cost and complexity as the element number increases, [ 47 , 48 ] limiting the spatial resolution at which PATs can create sophisticated wavefront manipulation.…”