Contactless energy transfer (CET) is a technology that is particularly relevant in applications where wired electrical contact is dangerous or impractical. Furthermore, it would enhance the development, use, and reliability of low-power sensors in applications where changing batteries is not practical or may not be a viable option. One CET method that has recently attracted interest is the ultrasonic acoustic energy transfer, which is based on the reception of acoustic waves at ultrasonic frequencies by a piezoelectric receiver. Patterning and focusing the transmitted acoustic energy in space is one of the challenges for enhancing the power transmission and locally charging sensors or devices. We use a mathematically designed passive metamaterial-based acoustic hologram to selectively power an array of piezoelectric receivers using an unfocused transmitter. The acoustic hologram is employed to create a multifocal pressure pattern in the target plane where the receivers are located inside focal regions. We conduct multiphysics simulations in which a single transmitter is used to power multiple receivers with an arbitrary two-dimensional spatial pattern via wave controlling and manipulation, using the hologram. We show that the multi-focal pressure pattern created by the passive acoustic hologram will enhance the power transmission for most receivers.
Many bio-medical applications entail the problems of spatially manipulating of bubbles by means of acoustic radiation.
The examples are ultrasonic noninvasive-targeted drug delivery and therapeutic applications. This paper investigates the
nonlinear coupling between radial pulsations, axisymmetric modes of shape oscillations and translational motion of a
single spherical gas bubble in a host liquid, when it is subjected to an acoustic pressure wave field. A mathematical model
is developed to account for both small and large amplitudes of bubble oscillations. The coupled system dynamics under
various conditions is studied. Specifically, oscillating behaviors of a bubble (e.g. the amplitudes and instability of
oscillations) undergoing resonance and off-resonance excitation in low- and high- intensity acoustic fields are studied.
Instability of the shape modes of a bubble, which is contributing to form the translational instability, known as dancing
motion, is analyzed. Dynamic responses of the bubble exposed to low- and high-intensity acoustic excitation are compared
in terms of translational motion and surface shape of the bubble. Acoustic streaming effects caused by radial pulsations of
the bubble in the surrounding liquid domain are also reported.
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