We present an accessible and versatile experimental technique that generates sub-kilohertz sinusoidal oscillatory flows within microchannels. This method involves the direct interfacing of microfluidic tubing with a loudspeaker diaphragm, which allows independent control of oscillation frequency and amplitude. Oscillatory flows were generated with frequencies ranging from 10 to 1000 Hz and amplitudes ranging from 10 to \(600 \ \upmu\)m. Fourier spectral analysis of particle trajectories, obtained by particle tracking velocimetry, was used to evaluate the oscillatory displacement in microchannels and shown to accurately represent simple harmonic motion specified by the loudspeaker. Oscillatory flow profiles in microchannels of square and rectangular cross-sections were characterized as a function of oscillation frequency, or Womersley number, and compared to theoretical benchmarks, such as Stokes flow and Stokes’ second problem. To highlight the versatility and effectiveness of the experimental method, prototypical applications were demonstrated utilizing pulsatile flow in microfluidic devices, such as inertial focusing and enhanced mixing at low Reynolds numbers.

我们提出了一种可访问且通用的实验技术，可在微通道内产生亚千赫兹正弦振荡流。该方法涉及将微流体管与扬声器膜片直接连接，从而可以独立控制振荡频率和幅度。产生的振荡流的频率范围为10到1000 Hz，幅度范围为10到\（600 \ \ upmu \）米 通过粒子跟踪测速法获得的粒子轨迹的傅立叶光谱分析，用于评估微通道中的振动位移，并显示为精确表示扬声器指定的简单谐波运动。将方形和矩形横截面的微通道中的振荡流剖面表征为振荡频率或沃默斯利数的函数，并将其与理论基准进行比较，例如斯托克斯流量和斯托克斯的第二个问题。为了突出实验方法的多功能性和有效性，在微流体装置中利用脉动流展示了原型应用，例如惯性聚焦和在低雷诺数下的增强混合。