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Abstract：
This study presents the design and development of an ultrasonic sensor as a fundamental tool for characterizing the properties of fluids and biofluids. The analysis primarily focuses on measuring the electrical parameters of the system, which correlate with the density and viscosity of the solutions, in sample volumes of microliters and with high temporal resolution (up to 1 data point per second). The use of this sensor allows the fast and non-destructive evaluation of the viscosity and density of fluids deposited on its free surface. The measurements are based on obtaining the impedance versus frequency curve and the phase difference curve (between current and voltage) versus frequency. In this way, characteristic parameters of the transducer, such as the resonance frequency, phase, minimum impedance, and the quality factor of the resonant system, can characterize variations in density and viscosity in the fluid under study. The results obtained revealed the sensor\'s ability to identify two parameters sensitive to viscosity and two parameters sensitive to density. As a proof of concept, the unfolding of the bovine albumin protein was studied, resulting in a curve that reflects its unfolding kinetics in the presence of urea.
摘要：
本研究提出了超声波传感器的设计和开发，作为表征流体和生物流体特性的基本工具。分析主要集中在测量系统的电气参数,与溶液的密度和粘度相关，在微升的样品体积和高时间分辨率（高达每秒1个数据点）。该传感器的使用允许快速和无损地评估沉积在其自由表面上的流体的粘度和密度。测量基于获得阻抗对频率曲线和相位差曲线(电流和电压之间)对频率。这样,换能器的特征参数，例如共振频率，阶段,最小阻抗,以及谐振系统的品质因数，可以表征所研究流体中密度和粘度的变化。获得的结果揭示了传感器识别对粘度敏感的两个参数和对密度敏感的两个参数的能力。作为概念的证明，研究了牛白蛋白蛋白的展开，产生反映其在尿素存在下的展开动力学的曲线。
