Electromechanical and Dynamic Characterization of In-House-Fabricated Amplified Piezo Actuator

A diamond-shaped amplified piezo actuator (APA) fabricated using six multilayered piezo stacks with maximum displacement of 173 μm at 175V and the amplification factor of 4.3. The dynamic characterization of the actuator was carried out at different frequencies (100 Hz–1 kHz) and at different AC voltages (20V–40V). The actuator response over this frequency range was found neat, without attenuation of the signal. Numerical modeling of multilayered stack actuator was carried out using empirical equations, and the electromechanical analysis was carried out using ABAQUS software. The block force of the APA was 81 N, calculated by electromechanical analysis. This is similar to that calculated by dynamic characterization method

Flexible Strain Detection Using Surface Acoustic Waves: Fabrication and Tests

Over the last couple of decades, smart transducers based on piezoelectric materials have been used as sensors in a wide range of structural health monitoring applications. Among them, a Surface Acoustic Wave sensor (SAW) offers an overwhelming advantage over other commercial sensing technologies due to its passive, small size, fast response time, cost-effectiveness, and wireless capabilities. Development of SAW sensors allows investigation of their potential not only for measuring less-time dependent parameters, such as pressure and temperature, but also dynamic parameters like mechanical strains. The objective of this study is to develop a passive flexible SAW sensor with optimized piezoelectric properties that can detect and measure mechanical strains occurred in aerospace structures. This research consists of two phases. First, a flexible thin SAW substrate fabrication using hot-press made of polyvinylidene fluoride (PVDF) as a polymer matrix, with lead zirconate titanate (PZT), calcium copper titanate (CCTO), and carbon nanotubes (CNTs) as micro and nanofillers’ structural, thermal and electrical properties are investigated. Piezoelectric property measurements are carried out for different filler combinations to optimize the suitable materials, examining flexibility and favorable characteristics. Electromechanical properties are enhanced through a noncontact corona poling technique, resulting in effective electrical coupling. Second, the two-port interdigital transducers (IDTs) deposition made of conductive paste onto the fabricated substrate through additive manufacturing is studied. Design parameters of SAW IDTs are optimized using a second-order transmission matrix approach. An RF input signal excites IDTs and generates Rayleigh waves that propagate through the delay line. By analyzing the changes in wave characteristics, such as frequency shift and phase response, the developed passive strain sensor can measure mechanical strains

HIGH PERFORMANCE PIEZOELECTRIC MATERIALS AND DEVICES FOR MULTILAYER LOW TEMPERATURE CO-FIRED CERAMIC BASED MICROFLUIDIC SYSTEMS

The incorporation of active piezoelectric elements and fluidic components into micro-electromechanical systems (MEMS) is of great interest for the development of sensors, actuators, and integrated systems used in microfluidics. Low temperature cofired ceramics (LTCC), widely used as electronic packaging materials, offer the possibility of manufacturing highly integrated microfluidic systems with complex 3-D features and various co-firable functional materials in a multilayer module. It would be desirable to integrate high performance lead zirconate titanate (PZT) based ceramics into LTCC-based MEMS using modern thick film and 3-D packaging technologies. The challenges for fabricating functional LTCC/PZT devices are: 1) formulating piezoelectric compositions which have similar sintering conditions to LTCC materials; 2) reducing elemental inter-diffusion between the LTCC package and PZT materials in co-firing process; and 3) developing active piezoelectric layers with desirable electric properties. The goal of present work was to develop low temperature fired PZT-based materials and compatible processing methods which enable integration of piezoelectric elements with LTCC materials and production of high performance integrated multilayer devices for microfluidics. First, the low temperature sintering behavior of piezoelectric ceramics in the solid solution of Pb(Zr0.53,Ti0.47)O3-Sr(K0.25, Nb0.75)O3 (PZT-SKN) with sintering aids has been investigated. 1 wt% LiBiO2 + 1 wt% CuO fluxed PZT-SKN ceramics sintered at 900oC for 1 h exhibited desirable piezoelectric and dielectric properties with a reduction of sintering temperature by 350oC. Next, the fluxed PZT-SKN tapes were successfully laminated and co-fired with LTCC materials to build the hybrid multilayer structures. HL2000/PZT-SKN multilayer ceramics co-fired at 900oC for 0.5 h exhibited the optimal properties with high field d33 piezoelectric coefficient of 356 pm/V. A potential application of the developed LTCC/PZT-SKN multilayer ceramics as a microbalance was demonstrated. The final research focus was the fabrication of an HL2000/PZT-SKN multilayer piezoelectric micropump and the characterization of pumping performance. The measured maximum flow rate and backpressure were 450 μl/min and 1.4 kPa respectively. Use of different microchannel geometries has been studied to improve the pumping performance. It is believed that the high performance multilayer piezoelectric devices implemented in this work will enable the development of highly integrated LTCC-based microfluidic systems for many future applications

Additive manufacturing (3D print) of air-coupled diaphragm ultrasonic transdrucers

Air-coupled ultrasound is a non-contact technology that has become increasingly common in Non Destructive Evaluation (NDE) and material evaluation. Normally, the bandwidth of a conventional transducer can be enhanced, but with a cost to its sensitivity. However, low sensitivity is very disadvantageous in air-coupled devices. This thesis proposes a methodology for improving the bandwidth of an air-coupled micro-machined ultrasonic transducer (MUT) without sensitivity loss by connecting a number of resonating pipes of various length to a cavity in the backplate. This design is inspired by the pipe organ musical instrument, where the resonant frequency (pitch) of each pipe is mainly determined by its length. The −6 dB bandwidth of the "pipe organ" inspired air-coupled transducer is 55.7% and 58.5% in transmitting and receiving modes, respectively, which is ∼5 times wider than a custom-built standard device. After validating the concept via a series of single element low-frequency prototypes, two improved designs: the multiple element and the high-frequency single element pipe organ transducers were simulated in order to tailor the pipe organ design to NDE applications.Although the simulated and experimental performance of the pipe organ inspired transducers are proved to be significantly better than the conventional designs, conventional micro-machined technologies are not able to satisfy their required 3D manufacturing resolution. In recent years, there has been increasing interest in using additive manufacturing (3D printing) technology to fabricate sensors and actuators due to rapid prototyping, low-cost manufacturing processes, customized features and the ability to create complex 3D geometries at micrometre scale. This work combines the ultrasonic diaphragm transducer design with a novel stereolithographic additive manufacturing technique. This includes developing a multi-material fabrication process using a commercial digital light processing printer and optimizing the formula of custom-built functional (conductive and piezoelectric) materials. A set of capacitive acoustic and ultrasonic transducers was fabricated using the additive manufacturing technology. The additive manufactured capacitive transducers have a receiving sensitivity of up to 0.4 mV/Pa at their resonant frequency.Air-coupled ultrasound is a non-contact technology that has become increasingly common in Non Destructive Evaluation (NDE) and material evaluation. Normally, the bandwidth of a conventional transducer can be enhanced, but with a cost to its sensitivity. However, low sensitivity is very disadvantageous in air-coupled devices. This thesis proposes a methodology for improving the bandwidth of an air-coupled micro-machined ultrasonic transducer (MUT) without sensitivity loss by connecting a number of resonating pipes of various length to a cavity in the backplate. This design is inspired by the pipe organ musical instrument, where the resonant frequency (pitch) of each pipe is mainly determined by its length. The −6 dB bandwidth of the "pipe organ" inspired air-coupled transducer is 55.7% and 58.5% in transmitting and receiving modes, respectively, which is ∼5 times wider than a custom-built standard device. After validating the concept via a series of single element low-frequency prototypes, two improved designs: the multiple element and the high-frequency single element pipe organ transducers were simulated in order to tailor the pipe organ design to NDE applications.Although the simulated and experimental performance of the pipe organ inspired transducers are proved to be significantly better than the conventional designs, conventional micro-machined technologies are not able to satisfy their required 3D manufacturing resolution. In recent years, there has been increasing interest in using additive manufacturing (3D printing) technology to fabricate sensors and actuators due to rapid prototyping, low-cost manufacturing processes, customized features and the ability to create complex 3D geometries at micrometre scale. This work combines the ultrasonic diaphragm transducer design with a novel stereolithographic additive manufacturing technique. This includes developing a multi-material fabrication process using a commercial digital light processing printer and optimizing the formula of custom-built functional (conductive and piezoelectric) materials. A set of capacitive acoustic and ultrasonic transducers was fabricated using the additive manufacturing technology. The additive manufactured capacitive transducers have a receiving sensitivity of up to 0.4 mV/Pa at their resonant frequency

Enhanced Piezoelectric Performance of Printed PZT Films on Low Temperature Substrates

Since piezoelectric effect was discovered in 1880, it has been widely used in micro-actuators, sensors, and energy harvesters. Lead Zirconate Titanate (PZT) is a commonly used piezoelectric material due to the high piezoelectric response. The basic PZT film fabrication process includes deposition, sintering, and poling. However, due to the high sintering temperature (\u3e 800 °C) of PZT, only high melting point material can be served as the substrate. Otherwise, complex film transfer approach is needed to achieve flexible and foldable PZT devices. The exploration is accordingly necessary to realize direct fabrication of PZT films on low melting point substrates without affecting the piezoelectric performance. In order to lower the PZT film sintering temperature, in this work, the effect of the powder size and sintering aid on the sintering temperature was studied. A maskless, CAD driven, non-contact direct printing system, aerosol jet printer, was used to deposit PZT thick films on the substrate. This technique allows creating features without masking and etching processes that are generally required for realizing designed features via conventional deposition approaches. Broadband, sub-millisecond, high intensity flash pulses were used to sinter the PZT films. The role of all sintering parameters was investigated to regulate the sintering quality of the PZT thick films. The photonically sintered films showed much lower substrate temperature increase mainly due to the extremely short pulse duration and temperature gradient through the film thickness. The superior piezoelectric property to thermally sintered group was also obtained. This process significantly shortens the processing duration and dramatically expands the possible substrate materials. It accordingly opens the possibility of processing PZT film directly on low melting point materials. A PZT energy harvester based on this process was directly fabricated on the polyethylene terephthalate (PET) substrate to demonstrate the capability. The relation between the load and the generated power was investigated to obtain the highest output power. Up to 0.1 μW was generated from this flexible energy harvester when connected with 10 MΩ resistive load. Photonic sintering of PZT film also creates the opportunity of processing poling during sintering. Different combinations of the sintering and poling techniques were studied. It was observed that the best piezoelectric property was obtained while performing poling during photonic sintering. Consequently, a new method of printing, sintering, and poling of micro-scaled PZT films was demonstrated in this work resulting in high performance films. This process provides the capability of realizing PZT devices on low temperature substrate, facilitates the fabrication of flexible piezoelectric devices, and enhances the piezoelectric property

Piezoelectric Devices in the Sustainable Society

Our 21st century faces to a “sustainable society”, which enhances (a) usage of non-toxic materials, (b) disposal technology for existing hazardous materials, (c) reduction of contamination gas, (d) environmental monitoring system, (e) new energy source creation, and (f) energy-efficient device development in the piezoelectric area. With reducing their size, the electromagnetic components reduce their efficiency drastically. Thus, piezoelectric transducers with much less losses are highly sought recently. Piezoelectric devices seem to be all-around contributors and a key component to the above mentioned five R&D areas. Some of the efforts include: (a) Since the most popular piezoelectric lead zirconate titante ceramics will be regulated in European and Asian societies due to their toxicity (Pb2+ ion), lead-free piezoelectrics have been developed. (b) Since hazardous organic substances can easily be dissolved by the ultrasonic irradiation in water, a new safe disposal technology using piezoelectric transducers has been developed. (c) We demonstrated an energy recovery system on a hybrid car from its engine’s mechanical vibration to the rechargeable battery. (d) Micro ultrasonic motors based on piezoelectrics demonstrated 1/20 reduction in the volume and a 20-time increase in efficiency of the conventional electromagnetic motors. This paper introduces leading piezoelectric materials, devices, and drive/control methods, relating with the above “sustainability” technologies, aiming at further research expansion in this area