EAGER: A Novel 3-D Printed PVDF-TrFE Copolymer Wall Shear Stress Measuring Device for Measurement of Wall Shear Stress in Unsteady Flow Applications

在气动和生理流动应用中，壁面剪应力测量和剪应力的影响是至关重要的。虽然在空气动力学和生理流体流动研究方面有广泛的文献，但对非定常流动的许多基本特性了解很少。在各种非恒定流模型的实验验证中，一个主要的限制是没有足够的流动测量仪器，特别是一种直接非侵入性测量壁面剪应力的方法。在复杂的非定常流动中评估壁面剪切应力所需的灵敏度和准确性是现有最先进的测量技术所无法达到的。本研究旨在研究一种多层三维印刷聚偏氟乙烯-三氟乙烯(PVDF-TrFE)共聚物传感器，作为壁面剪应力测量的候选器件。与现有方法相比，该技术的优点在于它不包含移动部件，可以直接测量壁面剪应力，可以直接安装在流动表面上，并且制造起来很容易。初步研究结果表明，PVDF-TrFE对挠度具有极高的灵敏度，具有较高的精度和灵敏度。本研究将致力于将这一新型传感器技术应用于非定常流动中的直接壁面剪应力测量。这项研究工作将解决与灵敏度、传感器的安装、使用粒子成像测速仪进行的壁面剪切应力测量以及泊松、沃姆斯利和斯托克斯流动的精确解析解的传感器测量验证相关的问题，以及传感器厚度引入的误差问题。如果建议的工作成功，建议的方法将为各种尺寸的平装式传感器提供制造和实施的简便性，这些传感器消除了移动部件，增加了坚固性，降低了流动仪器工具的成本，并提供了非侵入性的壁面剪切应力测量。PVDF-TrFE传感器从未被测试或用于壁面剪切传感，因此提供剪切传感的机电耦合机制还不完全清楚。这项开创性的研究工作将确定PVDF-TrFE在壁面剪切下的基本传感特性，改进传感器制造和封装，并将开发一种高频动态校准方法。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Wall shear stress measurements and the influence of shear stresses in aerodynamic and physiological flow applications are vital. Although there is widespread literature in aerodynamic and physiological fluid flow research, many of the basic properties of unsteady flows are poorly understood. A major limitation in the experimental validation of various unsteady flow models is insufficient flow measurement instrumentation, specifically a method of direct non-invasive measurement of wall shear stress. The sensitivity and accuracy needed to evaluate the wall shear stresses in complex unsteady flows is not attainable with the existing state-of-the-art measurement technologies. This research effort aims to investigate a multi-layered 3-D printed piezoelectric polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) copolymer sensor as a wall shear stress measuring device candidate. The proposed technology has an advantage in that it contains no moving parts, can potentially perform a direct measurement of wall shear stress, can be mounted directly to the flow surface with no modification, and can be manufactured easily as compared to existing methods. Preliminary results demonstrate that PVDF-TrFE exhibits exceptional sensitivity to deflection with high accuracy and sensitivity.This research effort will focus on implementing this novel sensor technology to perform direct wall shear stress measurements in unsteady flow applications. This research effort will address issues related to sensitivity, installation of the sensor, validation of sensor measurements with particle imaging velocimetry wall shear stress measurements and with exact analytical solutions for Poiseuille, Womersley and Stokes flows, and issues of error introduced by the sensor thickness. If the proposed effort is successful, the proposed methodology will provide ease of fabrication and implementation for a range of sizes of flush mountable sensors that eliminate moving parts increasing robustness, provides a reduction of cost in flow instrumentation tools, and provides a non-intrusive wall shear stress measurement. PVDF-TrFE sensors have never been tested or used for wall shear sensing, thus the electromechanical coupling mechanism that provides shear transduction is not fully understood. This pioneering research effort will determine the fundamental sensing properties of PVDF-TrFE under wall shear, improve sensor fabrication and packaging, and will develop a methodology for high frequency dynamic calibration.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.