The development of techniques able to characterize and map the pressure field is crucial for the widespread use of acoustofluidic devices in biotechnology and lab-on-a-chip platforms. In fact, acoustofluidic devices are powerful tools for driving precise manipulation of microparticles and cells in microfluidics in non-contact modality. Here, we report a full and accurate characterization of the movement of particles subjected to acoustophoresis in a microfluidic environment by holographic imaging. The particle displacement along the direction of the ultrasound wave propagation, coinciding with the optical axis, is observed and investigated. Two resonance frequencies are explored, varying for each the amplitude of the applied signal. The trajectories of individual tracers, accomplished by holographic measurements, are fitted with the theoretical model thus allowing the retrieval of the acoustic energy densities and pressure amplitudes through full holographic analysis. The absence of prior calibration, being independent of the object shape and the possibility of implementing automatic analysis make the use of holography very appealing for applications in devices for biotechnologies.

中文翻译：

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通过全息延时成像检索微流体中的声能密度和局部压力幅度†

能够表征和绘制压力场的技术的开发对于在生物技术和芯片实验室平台中广泛使用声流体设备至关重要。实际上，声流体装置是用于以非接触方式驱动微流体中的微粒和细胞的精确操纵的强大工具。在这里，我们报告通过全息成像在微流体环境中进行声泳的粒子运动的完整和准确的表征。观察并研究了沿超声波传播方向与光轴一致的粒子位移。探索了两个共振频率，每个共振频率随所施加信号的幅度而变化。通过全息测量完成的单个示踪剂的轨迹，符合理论模型，因此可以通过完整的全息分析来检索声能密度和压力幅度。无需事先校准，不受物体形状的影响以及实现自动分析的可能性，使得全息照相技术在生物技术设备中的应用非常吸引人。