Morrell Mia C, Lee Julianne E, Grier David G
Department of Physics and Center for Soft Matter Research, New York University, New York, New York 10003, USA.
Cornell University, Ithaca, New York 14853, USA.
Phys Rev E. 2024 Apr;109(4-1):044901. doi: 10.1103/PhysRevE.109.044901.
Acoustic trapping uses forces exerted by sound waves to transport small objects along specified trajectories in three dimensions. The structure of the time-averaged acoustic force landscape acting on an object is determined by the amplitude and phase profiles of the sound's pressure wave. These profiles typically are sculpted by deliberately selecting the amplitude and relative phase of the sound projected by each transducer in large arrays of transducers, all operating at the same carrier frequency. This approach leverages a powerful analogy with holographic optical trapping at the cost of considerable technical complexity. Acoustic force fields also can be shaped by the spectral content of the component sound waves in a manner that is not feasible with light. The same theoretical framework that predicts the time-averaged structure of monotone acoustic force landscapes can be applied to spectrally rich sound fields in the quasistatic approximation, creating opportunities for dexterous control using comparatively simple hardware. We demonstrate this approach to spectral holographic acoustic trapping by projecting acoustic conveyor beams that move millimeter-scale objects along prescribed paths. Spectral control of reflections provides yet another opportunity for controlling the structure and dynamics of an acoustic force landscape. We use this approach to realize two variations on the theme of a wave-driven oscillator, a deceptively simple dynamical system with surprisingly complex phenomenology.
声阱利用声波施加的力在三维空间中沿着指定轨迹移动小物体。作用于物体的时间平均声学力场的结构由声压波的幅度和相位分布决定。这些分布通常是通过在大型换能器阵列中精心选择每个换能器投射的声音的幅度和相对相位来塑造的,所有换能器都在相同的载波频率下工作。这种方法利用了与全息光阱的强大类比,但代价是技术复杂性相当高。声学力场也可以通过组成声波的频谱内容来塑造,这是光无法做到的。预测单调声学力场时间平均结构的相同理论框架可以应用于准静态近似下频谱丰富的声场,从而为使用相对简单的硬件进行灵活控制创造机会。我们通过投射能使毫米级物体沿规定路径移动的声传输束来演示这种频谱全息声阱方法。反射的频谱控制为控制声学力场的结构和动力学提供了另一个机会。我们用这种方法实现了波动驱动振荡器主题的两种变体,这是一个看似简单但现象学却惊人复杂的动力学系统。