A Novel 3D-Printed Polyvinylidene Fluoride Trifluoroethylene Sensor With Broadband Response for Dynamic Wall Shear Stress Point-Type Measurement

Abstract

Abstract. Accurate measurement of wall shear stress (WSS) is essential for turbulence research, aerodynamic testing, and biomedical flow diagnostics, yet existing sensors remain constrained by limited bandwidth, high noise, or fabrication complexity. Microelectromechanical systems (MEMS) floating-element devices rarely exceed 1 kHz, invade flow, and require complex micromachining. Thermal MEMS are intrinsically frequency dependent with elevated noise floors, and ionic polymer–metal composites (IPMCs) lose fidelity above 100 Hz due to ion transport limitations. This article reports a 3D-printed poly(vinylidene fluoride–trifluoroethylene) (PVDF-TrFE) piezoelectric WSS sensor that uniquely combines broadband fidelity, low noise, and scalable fabrication. To evaluate measurement performance, two complementary approaches were employed. A custom 3D-printed shear-block apparatus was used as a preliminary feasibility test to impose mechanically induced shear stress, providing a reproducible calibration baseline and yielding a near-linear voltage–strain response with an average sensitivity of 7.835 mV/Pa with minimal hysteresis. To validate fluid-induced response, the sensor was mounted in an in-house developed Stokes-layer acoustic-excitation tube, where dynamic testing produced clear spectral signatures: fundamentals at 500 Hz and 1 kHz, nonlinear coupling at 2.046 kHz, and recovery of the fundamental at 5 kHz, extending operational bandwidth nearly an order of magnitude beyond MEMS devices and two orders beyond IPMCs. Baseline analysis confirmed an intrinsically low-noise floor, enabling reliable detection of weak stress without drift correction. Collectively, these findings establish 3D printable PVDF-TrFE sensors as a new class of broadband point measurement WSS sensors.