Fabrication and characterization of free-standing thick-film piezoelectric cantilevers for energy harvesting

Research into energy harvesting from ambient vibration sources has attracted great interest over the last few years, largely as a result of advances in the areas of wireless technology and low power electronics. One of the mechanisms for converting mechanical vibration to electrical energy is the use of piezoelectric materials, typically operating as a cantilever in a bending mode, which generate a voltage across the electrodes when they are stressed. Typically, the piezoelectric materials are deposited on a non-electro-active substrate and are physically clamped at one end to a rigid base. The presence of the substrate does not contribute directly to the electrical output, but merely serves as a mechanical supporting platform, which can pose difficulties for integration with other microelectronic devices. The aim of this paper is to describe a novel thick-film free-standing cantilever structure that does not use a supporting platform and has the advantage of minimising the movement constraints on the piezoelectric material, thereby maximising the electrical output power. Two configurations of composite cantilever structure were investigated; unimorph and multimorph. A unimorph consists of a pair of silver/palladium (Ag/Pd) electrodes sandwiching a laminar layer of lead zirconate titanate (PZT). A multimorph is an extended version of the unimorph with two pairs of Ag/Pd electrodes and three laminar sections of PZT

A free-standing, thick-film piezoelectric energy harvester

In this paper, free-standing structures in the form of cantilevers, fabricated by using a combination of conventional thick-film technology and sacrificial layer techniques, is proposed. These structures were designed to operate as energy harvesters at low-levels of ambient vibration and were characterised using a shaker table over a range of frequencies and acceleration levels. A cantilever with dimensions of 13.5 mm long by 9 mm wide and total thickness of 192 mum was found to have Youngpsilas modulus of 3.8times10 N/m2, effective mass of 0.035g and spring constant of 362 N/m. Samples of length 18 mm and functional elements (lead zirconate titanate, PZT) of thickness 80 mum were found to produce an output voltage of up to 130 mV at their resonant frequency of 229 Hz, for an acceleration level of 0.981 ms-2 when driving into a resistive load of 60 kOmega. The addition of a proof mass was shown to improve the electrical output power generation. In a series of experiments, the electric power generated by a beam having a proof mass of 2.2 g, resulted in a nine-fold improvement of output power compared to a device with no proof mass. The size of the proof mass is also an important factor in determining the output power of the device

Free-Standing Pb(Zr, Ti)O3 Thick-Films Prepared By a One-Step Air Co-Firing Technique

Combinations of conventional thick-film technology and sacrificial layer techniques were used to fabricate free-standing structures, in the form of cantilever beams. By taking advantage of the different thermal expansion coefficients between silver/palladium (Ag/Pd) and piezoceramic Pb(Zr, Ti)O3, it was possible to fabricate a flat, but angled cantilever. In this work, sandwich structures consisting of PZT layers and Ag/Pd conductors, with in either interdigitated (IDT) or plated electrode configurations were fabricated in order to investigate the structural strength and the characteristics of free-standing structures. Screen printed carbon was used as a sacrificial layer. In the final step of the process, this was burnt out at a temperature of 850 C in an air environment. This resulted in a free-standing, sandwich structure of PZT-Ag/Pd. In order to reduce the problems of process complexity, a one-step firing process was used, whereby the sacrificial layer was co-fired together with PZT-Ag/Pd layers. The measurement results showed that the materials have a piezoelectric charge coefficient, d31 of -25 pC/N and coupling coefficient, k31 of 0.125. The cantilever structures were found to have a maximum Q-factor of around 200, and produced useful amounts of electrical power when driving resistive loads at low acceleration levels

DESIGN, FABRICATION AND CHARACTERISATION OF FREE-STANDING THICK-FILM PIEZOELECTRIC CANTILEVERS FOR ENERGY HARVESTING

Research into energy harvesting from ambient vibration sources has attracted great interest over the last few years, largely due to the rapid development in the areas of wireless technology and low power electronics. One of the mechanisms for converting mechanical vibration to electrical energy is the use of piezoelectric materials, typically operating as a cantilever in a bending mode, which generate a voltage across the electrodes when they are stressed. Traditionally, the piezoelectric materials are deposited on a non-electro-active substrate and are physically clamped at one end to a rigid base, which serves as a mechanical supporting platform. In this research, a three dimensional thick-film structure in the form of a free-standing cantilever incorporated with piezoelectric materials is proposed. The advantages of this structure include minimising the movement constraints on the piezoelectric, thereby maximising the electrical output and offering the ability for integration with other microelectronic devices. A series of free-standing composite cantilevers in the form of unimorphs were fabricated and characterised for their mechanical and electric properties. The unimorph structure consists of a pair of silver/palladium (Ag/Pd) electrodes sandwiching a laminar layer of lead zirconate titanate (PZT). An extended version of this unimorph, in the form of multimorph was fabricated to improve the electrical output performance, by increasing the distance of the piezoelectric layer from the neutral axis of the structure. This research also discusses the possibility of using an array of free-standing cantilevers in harvesting vibration energy in a broader bandwidth from an unpredictable ambient environment

A Novel Pieszoelectric Thick-FIlm Free-Standing Cantilever Energy Harvester

Research on energy harvesting from ambient vibration sources has been attracting tremendous attention recently. Free-standing piezoelectric structures are among the devices used as the energy harvester. The structures are commonly fabricated by using thin-film technology. However, their electromechanical properties are typically lower than those of thick-film materials. In this paper, a method of fabricating thick-film free-standing cantilevers, operated in d31 and d33 are described and the measurement results are presented. These devices are able to be operated at relatively low level of vibrations (frequencies below 500 Hz and acceleration levels below 10 m/s2) in ambient environment

Free-standing thick-film piezoelectric multimorph cantilevers for energy harvesting

Piezoelectric materials provide one approach for converting mechanical to electrical energy and can therefore be used to harvest energy from ambient vibration sources. Typically, piezoelectric materials are fabricated onto thin substrates, such as aluminum and stainless steel. These serve as mechanical support platforms to function as a cantilever beam structure. The platforms, however, are non-electro-active and they do not contribute directly to the electrical power output. The aim of this paper is to describe a novel multimorph cantilever structure in a free-standing form. Multimorphs consist of three laminar sections of lead zirconate titanate (PZT) of equal thickness 40 ¿m and length 18 mm were polarized in two modes; series and parallel. An optimum output power of 42 ¿W was measured when the series polarized sample was excited at its resonant frequency of 400 Hz

Fabrication and characterization of free-standing thick-film piezoelectric cantilevers for energy harvesting

Research into energy harvesting from ambient vibration sources has attracted great interest over the last few years, largely as a result of advances in the areas of wireless technology and low-power electronics. One of the mechanisms for converting mechanical vibration to electrical energy is the use of piezoelectric materials, typically operating as a cantilever in a bending mode, which generate a voltage across the electrodes when they are stressed. Typically, the piezoelectric materials are deposited on a non-electro-active substrate and are physically clamped at one end to a rigid base. The presence of the substrate does not contribute directly to the electrical output, but merely serves as a mechanical supporting platform, which can pose difficulties for integration with other microelectronic devices. The aim of this paper is to describe a novel thick-film free-standing cantilever structure that does not use a supporting platform and has the advantage of minimizing the movement constraints on the piezoelectric material, thereby maximizing the electrical output power. Two configurations of the composite cantilever structure were investigated: unimorph and multimorph. A unimorph consists of a pair of silver/palladium (Ag/Pd) electrodes sandwiching a laminar layer of lead zirconate titanate (PZT). A mulitmorph is an extended version of the unimorph with two pairs of Ag/Pd electrodes and three laminar sections of PZT

Novel Thick-Film Piezoceramic Micro-Generator Based on Free-Standing Structures

Thick-film piezoelectric free-standing structures fabricated with a combination of conventional thick-film technology and a sacrificial layer technique are presented. The structures were fabricated in the form of composite cantilevers, consisting of lead zirconate titanate (PZT) as the functional element and silver/palladium (Ag/Pd) as the electrodes. The cantilevers are free standing above a substrate and are able to operate at low levels of vibration suitable for harvesting energy from the environment. An open circuit output voltage of 130 mV was measured from a sample of length 18 mm, width 9 mm and PZT thickness of 80 μm. The sample was found to produce a maximum output electrical power of 10 nW at its resonant frequency of 237.5 Hz and acceleration level of 0.981 m/s2 when driving a 60 kΩ resistive load. The output power was found to increase exponentially with acceleration. At an acceleration of 9.81 ms-2, 270 nW of power was produced. The output power can be improved by attaching a proof mass at the tip of the cantilever beam. A beam having a proof mass of 1.14 g, resulted in an eight-fold improvement of output power compared to a device with no added proof mass at the same acceleration level of 0.98 ms-2

Effect of green innovation strategy on firm-idiosyncratic risk: A competitive action perspective

Despite increasing concern for corporate environmental responsibility in numerous industries, the relationship between green innovation strategy (GIS) and idiosyncratic risk is a rarely scrutinised topic, particularly in the automotive domain. In this study, we empirically explore the association between GIS and idiosyncratic risk and analyse the moderating role played by the firm's competitive action. We rely on the secondary information sourced for 132 top automotive firms, in the period ranging from 2011 to 2017 by applying the system generalised methods of moments estimator to the dynamic panel data model. Our findings indicate that GIS significantly reduces the idiosyncratic risk of all firms, and this relationship strengthens with the increase in the competitive action of the firms. Our evidence supports “it pays to be green” firm heterogeneity argument. This study highlights the academic and managerial implications and focuses on the environmental issues published in environmental management literature

Corporate debt policy of Malaysian SMEs: empirical evidence from firm dynamic panel data

Financing has been identified as a dominant constraint to Malaysian small and medium-sized enterprises (SMEs). Yet, limited attention has been given to the challenges faced by the SMEs in financing their operations. This paper investigates the determinants of capital structure and use of financing for Malaysian SMEs in manufacturing sector and examines hypotheses by utilising a static trade-off choice or pecking order framework by employing a series of firm characteristics including: size, age, asset structure, profitability, growth, taxation and risk. The system Generalised Method of Moment (GMM) approach has been used for the estimation. The findings suggest that most of the determinants of capital structure presented by the theory of finance appear to be relevant for the Malaysian SMEs. Firm size and asset structure have a significantly positive effect on the leverage ratio in SMEs, while age and taxation have a negative effect. Though, growth has an impact on the total debt of the firms, profitability and risk does not have any significant effect on the decision of debt decision making in Malaysian SMEs. Furthermore, the findings of the study show that Malaysian SMEs in the manufacturing sector generally operate based on a combination of the pecking order and the trade-off theory while borrowing in the long-term and short-term