Mouro João, Paoletti Paolo, Sartore Marco, Vassalli Massimo, Tiribilli Bruno
Institute for Complex Systems, National Research Council (ISC-CNR), 50019 Florence, Italy.
School of Engineering, University of Liverpool, Liverpool L69 3GH, UK.
Sensors (Basel). 2022 Nov 2;22(21):8421. doi: 10.3390/s22218421.
This work presents a feedback closed-loop platform to be used for viscosity or viscoelasticity sensing of Newtonian or non-Newtonian fluids. The system consists of a photothermally excited microcantilever working in a digital Phase-Locked Loop, in which the phase between the excitation signal to the cantilever and the reference demodulating signals is chosen and imposed in the loop. General analytical models to describe the frequency and amplitude of oscillation of the cantilever immersed in viscous and viscoelastic fluids are derived and validated against experiments. In particular, the sensitivity of the sensor to variations of viscosity of Newtonian fluids, or to variations of elastic/viscous modulus of non-Newtonian fluids, are studied. Interestingly, it is demonstrated the possibility of controlling the sensitivity of the system to variations of these parameters by choosing the appropriate imposed phase in the loop. A working point with maximum sensitivity can be used for real-time detection of small changes of rheological parameters with low-noise and fast-transient response. Conversely, a working point with zero sensitivity to variations of rheological parameters can be potentially used to decouple the effect of simultaneous external factors acting on the resonator.
这项工作展示了一个反馈闭环平台，用于对牛顿流体或非牛顿流体进行粘度或粘弹性传感。该系统由一个在数字锁相环中工作的光热激发微悬臂梁组成，在该锁相环中，选择施加到悬臂梁的激励信号与参考解调信号之间的相位并在环路中加以设定。推导了用于描述浸没在粘性和粘弹性流体中的悬臂梁振荡频率和幅度的通用分析模型，并通过实验进行了验证。特别地，研究了传感器对牛顿流体粘度变化或非牛顿流体弹性/粘性模量变化的灵敏度。有趣的是，通过在环路中选择合适的施加相位，证明了控制系统对这些参数变化灵敏度的可能性。具有最大灵敏度的工作点可用于以低噪声和快速瞬态响应实时检测流变参数的微小变化。相反，对流变参数变化零灵敏度的工作点可潜在地用于解耦同时作用于谐振器的外部因素的影响。
