1,721,051 research outputs found
Experimental investigation into the effect of substrate clamping on the piezoelectric behaviour of thick-film PZT elements
No full textThis paper details an experimental investigation of the clamping effect associated with thick-film piezoelectric elements printed on a substrate. The clamping effect reduces the measured piezoelectric coefficient, d33, of the film. This reduction is due to the influence of the d31 component in the film when a deformation of the structure occurs, by either the direct or indirect piezoelectric effect. Theoretical analysis shows a reduction in the measured d33 of 62%, i.e. a standard bulk lead zirconate titanate (PZT)-5H sample with a manufacturer specified d33 of 593pC/N would fall to 227.8pC/N. To confirm this effect, the d33 coefficients of five thin bulk PZT-5H samples of 220µm thickness were measured before and after their attachment to a metallized 96% alumina substrate. The experimental results show a reduction in d33 of 74% from 529pC/N to 139pC/N. The theoretical analysis was then applied to existing University of Southampton thick-film devices. It is estimated that the measured d33 value of 131pC/N of the thick-film devices is the equivalent of an unconstrained d33 of 345pC/N
Development of a cantilever beam generator employing vibration energy harvesting
No full textThis paper details the development of a generator based upon a cantilever beam inertial mass system which harvests energy from ambient environmental vibrations. The paper compares the predicted results from Finite Element Analysis (FEA) of the mechanical behaviour and magnetic field simulations and experimental results from a generator. Several design changes were implemented to maximise the conversion of magnetic energy into generated power and a maximum power output of 17.8µW was achieved at a resonant frequency of 56.6Hz and an applied acceleration of 60mg (g = 9.81ms-2)
An improved thick-film piezoelectric material by powder blending and enhanced processing parameters
No full textThis paper details improvements of the d33 coefficient for thick-film lead zirconate titanate (PZT) layers. In particular, the effect of blending ball and attritor milled powders has been investigated. Mathematical modeling of the film structure has produced initial experimental values for powder combination percentages. A range of paste formulations between 8:1 and 2:1 ball to attritor milled PZT powders by weight have been mixed into a screen-printable paste. Each paste contains 10% by weight of lead borosilicate glass and an appropriate quantity of solvent to formulate a screen printable thixotropic paste. A d33 of 63.5 pC/N was obtained with a combination of 4:1 ball milled to attritor milled powder by weight. The improved paste combines the high d33 values of ball and the consistency of attritor milled powder. The measured d33 coefficient was further improved to 131 pC/N by increasing the furnace firing pro-file to 100
Actively actuated all dispenser printed thermochromic smart fabric device
Full text linkAn all printed actively actuated thermochromic (TC) smart fabric device is reported for the first time using a state of the art dispenser printing technique. The device consists of an ultraviolet curable TC ink with an activation temperature of 33°C actuated by conductive track-based printed heater. The device is printed on untreated polyester cotton fabric. It offers a significant improvement in flexibility and design freedom over the state of the art TC fabric devices. The printed device changes colour from black to green in 10.8 s using 1.46 W DC power. It is shown that the time required for the device to change colour reduces tenfold with only a threefold increase in input power. It can be fabricated on other fabric or flexible substrates and in a range of colours and activation temperatures depending on the formulation chosen. The printed device is 30 × 21.5 mm which can be scaled up or down to suit the application. It can be used as an indicator in combination with sensors for smart fabric applications
Thick-film Piezoceramics and Devices
No full textOver the past 20 years, thick-film (screen printed) technology has been shown to possess a variety of desirable characteristics, which are particularly suitable for the realisation of micro-sensors and actuators. In particular, thick-film sensors are noted for their robust, versatile, compact and inexpensive nature. This paper will describe how screen printed thick-films can be used as the basis for a variety of piezoelectric a transducers. It will be shown how the technology can be combined with MicroElectroMechanical Systems (MEMS) to generate new types of microengineered structure. The evolution of the technology to a successful enabling mechanism for modern-day solid state sensors is described. The paper begins with a brief overview of piezoelectric thick-films including a discussion of the main factors relating to paste formulation, characterisation and techniques for fabricating devices. There is also a description of methods for fabricating thick-films on silicon, which opens up the possibility of using thick-film technology in the field of MEMS. A number of specific sensors and actuators are described, including accelerometers, micropumps, ultrasonic motors, slip sensors for prosthetic hands, resonators, elastic wave sensors and ultrasonic separators
A study of powder size combinations for improving piezoelectric properties of PZT thick-film devices
No full textThis paper details investigations into the effects of different powder size ratios on the d33 coefficient of thick-film PZT layers. The two powders used were 5H type PZT supplied by Morgan Electro Ceramics Ltd. These were prepared using ball milling for the large particles, ~2µm, and attritor milling for the small particles, ~1µm. These powders were mixed with 10% by weight of Ferro CF7575 lead borosilicate glass and an appropriate quantity of ESL 400 solvent to formulate a screen printable paste. The results show the optimum powder combination obtained and a final formulation for a practical thick-film paste. The highest d33 value, 63.5pC/N, was obtained with the 4:1 ball to attritor powder by weight paste formulation
Wireless sensor system powered by an electromagnetic vibration energy harvester
No full textThis paper describes a microscale electromagnetic vibration powered generator that harvests kinetic energy and provides a localised power supply for wireless applications. The generator is as resonant device and therefore the power output depends upon the size of the inertial mass, the frequency and amplitude of the driving vibrations, the maximum available mass displacement and the damping. The electromagnetic generator has been implemented with discrete components and produces 58 ?Wrms at 0.6 ms-2 acceleration from a fixed frequency of 52 Hz and achieves the highest recorded efficiency to date of 51% for a device of this size. The packaged device is 0.8 cm3 and weighs 1.6 grams. The energy harvested is sufficient to power a wireless, accelerometer based microsystem. The microsystem is energy aware and will adjust the measurement/transmit duty cycle according to the available energy; this is typically every 3 seconds during normal operation
MICROFLEX project: microfabrication production technology for MEMS on new emerging smart textiles/flexibles
No full textPresentation on the Microflex project with 3 case studies discussing the pastes and inks developed during the project
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