A reconfigurable active acoustic metalens

Abstract

Acoustic metasurfaces have enabled unprecedented control over acoustic waves, offering opportunities in areas such as holographic rendering, sound absorption, and acoustic communication. Despite the steady progress made in this field, most acoustic metasurface designs are passive in that they only provide static functionalities. Here, a reconfigurable active acoustic metalens is implemented to showcase scanning of the focus along arbitrary trajectories in free space with the help of a previously developed active acoustic metasurface platform. Each unit cell of the metasurface contains a cavity, whose size can be tuned continuously by a dynamic control system to adjust the phase of the reflected wave. While this work focuses on beam focusing, it could hold great promise for a wide range of applications including acoustic levitation and tweezers.

Biomass-Derived Carbon Heterostructures Enable Environmentally Adaptive Wideband Electromagnetic Wave Absorbers

“…However, the frequent utilization of wireless electronics has led to the prevalence of electromagnetic (EM) pollution, which now ranks fourth after water, air, and noise pollution [1][2][3]. To mitigate EM pollution, EM absorbing materials have attracted lots of attention for their ability to convert ambient EM waves into Joule heat [4][5][6]. Extensive efforts have been made in the past to develop EM absorbers with wideband EM absorption [7][8][9].…”

Engineering defects in 2D g-C3N4 for wideband, efficient electromagnetic absorption at elevated temperature

“…Besides the health concerns associated with EM waves, EM pollution causes interference to device-to-device communication, which can be detrimental for a variety of applications ranging from self-driving vehicles to remote surgical operations. 3,4 Hence, harvesting the excess EM waves and converting them into thermal energy using a material design strategy (based on the material intrinsic dielectric relaxation and conductive loss) provides a feasible solution to address EM pollution. [5][6][7] The design criteria for an ideal EM absorber include strong EM absorption (calculated by reection loss (RL)), wideband effective absorption (f E ; frequency region with RL < À10 dB, corresponding to >90% EM absorption), small thickness (referring to the thickness of absorption layer made by dispersing the EM absorber into a matrix), and low mass density (lightweight).…”

Coiling-Up Space Metasurface for High-Efficient and Wide-angle Acoustic Wavefront Steering

“…Basically, the uniqueness of metasurfaces rested with their ability of easily adjusting the phase and/or amplitude so as to fully control the wave fields. At present, acoustic metasurfaces with various profiles have been proposed for different functions and applications, including (but not limited to) Helmholtz-resonator-like Wang et al, 2016;Zhang et al, 2021), membrane-type (Ma et al, 2014;Tang et al, 2019;Liu et al, 2020), and coiling-up space (Xie et al, 2014;Liang and Li, 2012;N. Almeida et al, 2021).…”