Institute of Mechanical Systems, Department of Mechanical and Process Engineering, ETH Zentrum, Zurich, Switzerland.
Lab Chip. 2012 Mar 7;12(5):852-62. doi: 10.1039/c2lc21067c. Epub 2012 Feb 2.
Because of uncertainties in material and geometrical parameters in ultrasonic devices, experimental characterization is an indispensable part in their successful application for the manipulation of particles or cells. Its miniaturized size precludes the use of many of the usual tools used for macroscopic systems. Also, a further challenge is the fact that the resulting motion due to the electromechanical actuation has both high frequency and small amplitudes. Contactless methods like laser interferometry are therefore promising methods. In addition, as long as there is strong electromechanical coupling between the transducer and the device also electrical measurements like admittance curves give insight into the frequencies at which the devices might work best. This is the case for example for piezoelectric transducers working at one of their resonance frequencies. Because the devices usually are used in resonant modes, narrow frequency detection methods like lock in amplifiers help to improve the signal to noise ratio. Also many analysis tools have been established in the context of modal analysis, which is based on frequency domain methods. Special emphasis is placed here on the determination of the quality factor Q of the resonator, as Q determines the efficiency of a device.
由于超声设备中的材料和几何参数存在不确定性，因此实验特性分析是成功应用于操控粒子或细胞的不可或缺的部分。由于其微型化尺寸，许多用于宏观系统的常用工具都无法使用。此外，另一个挑战是由于机电致动而产生的运动具有高频和小振幅。因此，非接触式方法（如激光干涉法）是很有前途的方法。此外，只要换能器和设备之间存在很强的机电耦合，像导纳曲线这样的电测量也可以深入了解设备可能工作的最佳频率。例如，对于工作在其一个共振频率的压电换能器就是如此。由于设备通常在谐振模式下使用，因此像锁相放大器这样的窄频检测方法有助于提高信噪比。此外，在基于频域方法的模态分析的背景下，已经建立了许多分析工具。这里特别强调确定谐振器的品质因数 Q，因为 Q 决定了设备的效率。
