Sound propagation in viscous flows using piezoelectric sensors and non-destructive propagation techniques and its applications

Structural non-destructive evaluation techniques are applied to viscous flows to detect fluid property changes. The main operating principle consists of an actuator which provides a stimulus, and a sensor to receive a signal traveling to a fluid domain. The main challenge of the operating principle consists of investigating waves traveling in a viscous flow. Traveling waves utilizing a piezoelectric actuator-sensor pair are modeled and the results are validated experimentally. ANSYS models, coupled with a two-way fluid-solid interaction model, are built to investigate how far a signal travels and what frequency ranges are of interest. The numerical model includes modeling three different geometries (square, circular, triangular) for the actuator-sensor pair manufactured with three different piezoelectric materials (PZT4, PZT5A, PMN32). Numerical work is validated with experimental work using a pair of circular actuator-sensors manufactured with PZT5A and immersed in a large container of water and glycerin. Furthermore, in order to establish mesh independence of the results, three mesh refinement levels (coarse, medium and fine) were utilized with different materials, geometries and fluid viscosity values. The actuator receives a 0.5 VAC signal ranging from 100 Hz to 40 MHz. The sensor records the signal at varying distances from the actuator, and the result is labeled as the gain or the ratio of received to send wave magnitude. The pattern of decay for both numerical and experimental results are in close agreement (the numerical decay are 10.825 and 11.4 for water and glycerin, respectively, while the experimental are 11.254 and 14.48 for water and glycerin, respectively). Numerically, the results show that the maximum acoustic pressure can be obtained by using a square piezoelectric actuator- sensor pair fabricated with PMN32. Numerically, the results show that the maximum acoustic pressure can be obtained by using a square piezoelectric actuator- sensor pair fabricated with PMN32. A viscosity probe for medical applications is developed using a piezoelectric actuator-sensor pair. The design constraints were size and cost. The actuator-sensor pair is manufactured with PZT5A with a rectangular shape to fit a 3 mL vacutainer. The actuator is excited by 0.5 VAC sinusoidal waves with varying frequencies ranging from 100Hz to 40 MHz. The sensor will detect the produced wave in the fluid. Also, the phase shift is recorded for different concentrations of glycerin and water to simulate different viscosities ranging from 1 to 1600 cP. The numerical analysis, a modal analysis, of the probe was performed and the results showed that the first, second and third modes of the device were in the range of 684–2358 Hz for air, 500–1080 Hz for water, and 469–625 Hz for glycerin. From the harmonic acoustic analysis, the results showed that the highest phase shifts, and maximum gain, occurs at the ultrasonic frequency range, 6 to 9 MHz. Hence, there is no relation between the natural frequencies of the probe and the ultrasonic frequency for the phase shift. Most importantly, a correlation between the phase shift and viscosity is found, making the probe a feasible device for measuring viscosity in an inexpensive, small, and disposable way

A MEMS Resonant Sensor to Measure Fluid Density and Viscosity under Flexural and Torsional Vibrating Modes

Methods to calculate fluid density and viscosity using a micro-cantilever and based on the resonance principle were put forward. Their measuring mechanisms were analyzed and the theoretical equations to calculate the density and viscosity were deduced. The fluid-solid coupling simulations were completed for the micro-cantilevers with different shapes. The sensing chips with micro-cantilevers were designed based on the simulation results and fabricated using the micro electromechanical systems (MEMS) technology. Finally, the MEMS resonant sensor was packaged with the sensing chip to measure the densities and viscosities of eight different fluids under the flexural and torsional vibrating modes separately. The relative errors of the measured densities from 600 kg/m3 to 900 kg/m3 and viscosities from 200 μPa·s to 1000 μPa·s were calculated and analyzed with different microcantilevers under various vibrating modes. The experimental results showed that the effects of the shape and vibrating mode of micro-cantilever on the measurement accuracies of fluid density and viscosity were analyzed in detail

Improvements to a Thermally Actuated MEMS Viscosity Sensor

Being able to measure and monitor the viscosity of a fluid accurately and in real-time can provide insights and prevent field failures of lubricated mechanical elements. A micro electro mechanical system (MEMS) viscosity sensor that measures the properties of liquids through thermal vibrations of a silicon membrane has been previously developed. The device measures viscosity through three different characteristics: the frequency, amplitude and the quality factor of the vibrating membrane. The membrane is actuated via a short pulse of heat delivered by the heater resistor provided by an external voltage. The pulse width is controlled by a waveform generator and a power MOSFET. The movement of the membrane is measured with an in-situ piezoresistor Wheatstone bridge, which is powered by an external voltage source, and amplified with and instrumentational amplifier before the resulting vibrating signal is analyzed in LabView. The end goal of this work is to characterize the sensitivity and real-time response of a thermally actuated MEMS viscosity sensor. In addition, a process modification to include a deep reactive ion etch instead of a KOH etch, has been developed. As viscosity is dependent on temperature, when the membrane is actuated by heat, the effects of locally changing the fluid temperature will affect the sensitivity of the sensor. Optimized test bias condition results were, Wheatstone bridge bias voltage when increased over 7 V, the natural frequency of vibration of the sensor is modified. Pulse width and heater bias value can be adjusted for optimum sensor response. With these established bias conditions, the real-time response of the system was investigated. Epoxy was used to cover the sensor perimeter, protect the 25 - micron aluminum wire bond connections to a copper PCB and to glue the sensor onto the PCB. Test result show a spike in frequency and amplitude when different oils were added. As shown with additional tests, the spike is mainly caused by slight temperature variations that are introduced with new oil and how they affect the sensor packaging. Spikes were reduced by lowering the bridge bias voltage from 7 V to 3 V, which minimized the sensor heating. Furthermore, addition of oil in very small quantities, in the µL range, reduced the changes in temperature. Figure 1 shows frequency and amplitude response with varying viscosities without agitation. During testing, when oil is added, the amplitude shows an immediate overdamped response which takes about 1-2 minutes to stabilize, whereas frequency is characterized by an underdamped response with response time 5-7 minutes. Frequency response time was slower as it is very dependent on intrinsic stresses of both sensor and packaging, whereas amplitude of oscillations seems to be more independent to these properties changing and shows faster response

Functionalized magnetoelastic resonant platforms for chemical and biological detection purposes

211 p.In recent years, research on magnetoelastic materials has focused on their applications as sensors to observe, measure and control different kind of physical, chemical and biological parameters, taking advantage of the remote query and answer of this kind of materials. In order to use those magnetoelastic materials for sensing purposes, they must be coated with an active layer which will be the responsible of selectively detect and trap the target molecule or analyte desired to be detected. This thesis work is devoted to different functionalization processes performed using different active materials as a polymer, ZnO or zeolites onto magnetoelastic materials. Polystyrene depositions allowed studying the main two parameters affecting the detection process, the sensitivity and the quality factor. By following the change on the resonance frequency with the deposited polymer mass it has been probed that the linearity of the detection process can be applied just for small-deposited mass changes.Different methods to form a homogenous ZnO film onto the magnetoelastic material were tried. Finally, ZnO depositions were performed by casting a nanoparticle suspension onto the Metglas materials. This allowed to measure by using the resonance-antiresonance method the Young modulus of the ZnO deposited film. As ZnO is biocompatible and allows protein immobilization, a H2O2 sensor was fabricated by pinning hemoglobin onto the ZnO layer. Hemoglobin reacts with hydrogen peroxide, which plays an important role in some physiological and biological processes. The response of the sensor was followed for first time by using simultaneously two methods, the magnetoelastic resonance method in order to study the evolution of the resonance frequency and by cyclic voltammetry measurements as the reaction between H2O2 and hemoglobin is electrochemical.The third material used to functionalize the resonant platforms were zeolites. Three different zeolites, LTA, FAU and MFI were hydrothermally synthesized onto a homemade magnetoelastic material in order to use those systems as sensor for o-xylene detection.BC Materials:basque center for materials, applications & nanostructure

Functionalized magnetoelastic resonant platforms for chemical and biological detection purposes

211 p.In recent years, research on magnetoelastic materials has focused on their applications as sensors to observe, measure and control different kind of physical, chemical and biological parameters, taking advantage of the remote query and answer of this kind of materials. In order to use those magnetoelastic materials for sensing purposes, they must be coated with an active layer which will be the responsible of selectively detect and trap the target molecule or analyte desired to be detected. This thesis work is devoted to different functionalization processes performed using different active materials as a polymer, ZnO or zeolites onto magnetoelastic materials. Polystyrene depositions allowed studying the main two parameters affecting the detection process, the sensitivity and the quality factor. By following the change on the resonance frequency with the deposited polymer mass it has been probed that the linearity of the detection process can be applied just for small-deposited mass changes.Different methods to form a homogenous ZnO film onto the magnetoelastic material were tried. Finally, ZnO depositions were performed by casting a nanoparticle suspension onto the Metglas materials. This allowed to measure by using the resonance-antiresonance method the Young modulus of the ZnO deposited film. As ZnO is biocompatible and allows protein immobilization, a H2O2 sensor was fabricated by pinning hemoglobin onto the ZnO layer. Hemoglobin reacts with hydrogen peroxide, which plays an important role in some physiological and biological processes. The response of the sensor was followed for first time by using simultaneously two methods, the magnetoelastic resonance method in order to study the evolution of the resonance frequency and by cyclic voltammetry measurements as the reaction between H2O2 and hemoglobin is electrochemical.The third material used to functionalize the resonant platforms were zeolites. Three different zeolites, LTA, FAU and MFI were hydrothermally synthesized onto a homemade magnetoelastic material in order to use those systems as sensor for o-xylene detection.BC Materials:basque center for materials, applications & nanostructure