Abstract
This research paper exhibits the design of a V-shaped cantilever beam as a micro Energy Harvester (EH) having Piezoelectric (PZT) as its energy source for biomedical applications. PZT source based materials have the ability to convert the mechanical energy into electrical energy. Low-power biomedical devices mostly operate using electrical energy (i.e. batteries). But batteries are treated as a bio-hazard due to the massive use of biomedical applications. To overcome this toxic bio-hazard, the proposed PZT based V-shaped cantilever beam of micro EH can solve the limitations. To perform the experimental work, the cantilever beam design parameters - length, width and thickness have been considered and simulated using COMSOL Multiphysics to get the resonant frequency of 156.19 Hz which is lower than previous research work. It was observed that the obtained lower resonant frequency can be converted into AC voltage (mV) using PZT material. To convert the output AC voltage (mV) into DC voltage, a circuit of an Ultra-Low-Power (ULP) EH will be designed in LTSPICE software. Finally, the integration of the both V-shape cantilever beam and the ULP EH circuit will be implemented in PCB hardware to generate the output power (10 µW), will be stored in super-capacitor for biomedical devices-pacemaker.
1 Introduction
In past decades, numerous strategies for producing piezoelectricity have emerged. Low-voltage semiconductor devices can deliver power to electronic equipment with low power consumption [1, 2]. Alireza Khaligh et al. [3] showed several different techniques in their research to produce low-power voltage using sources of solar, thermal, wind energy and vibration. Starner et al. [4] discussed on the limited capacity of these sources in providing useful power.
The Shape Memory Alloy (SMA) is heated from a distant location using a laser and the deformation that occurs due to heating, is transformed into power using a piezoelectric bimorph [5, 6]. A prototype of an active energy harvesting technique uses such SMA and piezoelectric devices to convert ambient heat energy into electrical energy. According to Mehraeen et al. [7] the cantilever beam using vibration as one of the sources generates piezoelectricity. The phenomena of piezoelectricity are well-known in every single region of the world. It is used to provide power to electronic equipment with a low power requirement. Experimental and analytical methods have been offered by researchers P.K. et al. [8] in order to determine the natural frequencies of microbeams. Despite this, relatively little effort has been put into developing a model which is capable of giving a comprehensive vibration response by the micro-cantilever beams when loads-in-vibration are applied. Micro-Electro-Mechanical-Systems (MEMS) applications that use them include wind speed sensors, RF switching, biosensors and chemical sensor arrays. The goal of this research was to provide a theoretical framework for estimating the vibrational response to applied forces on micro-cantilever beams subjected to both constant and variable spatial loads. Nagoya Kōgyō Daigaku et al. [9] shows that their findings of the three different thicknesses of the film paves the linearity of the film which is preserved regardless of thickness. The deflection is reduced for the thinner films as compared to the thicker ones. According to Damircheli et al. [10], researchers have been looking at the outcome effects that the V-shaped cantilevers' geometrical dimensions have on some static and dynamic parameters and higher bending modes vibrations and the multifrequency characterized Atomic-Force-Microscopy (AFM). The considered characteristics are cantilever length, top width, bottom width and thickness. A cantilever in the V-shape based on the AFM measurements has been designed in this article. The vibration energy of this device determines the frequency variants whereas the changes of varying frequencies depend on their lengths.
In the paper, Atzori et al. [11] have seen a shift in the emphasis placed on the research and development of analog combined circuits because of the propagation of energy signals to portable device-circuits, implantable circuits of biomedical systems, the rapid development of hybrid-energy harvesting systems for some self-powered wireless sensor and Internet of Things (IoT) modules. Energy constraints are a crucial need for wireless and transmission devices. For example, communication devices require frequent charging which is time-consuming. According to [12–14], energy harvesting has emerged as a promising technique that has the potential to alleviate the issue of limited energy resources in communication devices. Thermoelectric generators, Radio Frequency, and Vibration are the three hybrid energy sources that can be produced using Ultra-Low Power (ULP) circuits. Thermoelectric generators are dependent on the heat or temperature of their surroundings. Intentional transmission of radio frequencies can be accomplished by both antennas and mobile phones. The motor or other shaking devices are the sources of the vibration. An analysis of the hybrid energy harvester's vibration can be found virtually anywhere. It is anticipated that it will be the most effective method of producing electrical power.
Recently there has been an increase in interest in using human movement to gather energy in biomedical applications. Lower frequencies are generally preferred for biomedical applications because the movements and vibrations associated with biological processes often occur at low frequencies. This makes it more efficient to harvest energy from these processes using devices that operate at lower frequencies. Jinthujah Selvarathinam et al. [15] conducted an experiment to generate power by using the movement of human body parts vibration. In the context of energy harvesting for pacemakers, the most effective human body movement for generating electricity is typically the motion of the heart itself. The motion of the heart generates mechanical energy that can be harnessed using piezoelectric or electromagnetic generators to power the pacemaker.
The goal of this study is to design a V-shape cantilever beam in COMSOL Multiphysics 5.5 version software and integrate it with the developed electrical circuit in LTSPICE simulation for Biomedical applications - pacemakers.
2 Literature review
The cantilever beam comprises several shapes such as rectangular, array, T-shape and V-shape. Some research is being conducted on every aspect of various shapes which are discussed below:
Iqbal et al. [16] indicated that seven cantilever beams as a preferred straight beam, straight-tapered beam, T beam, U beam, V beam, V-T beam and Y beam. It also describes which one is the most suitable for generating electrical energy. The beams were designed with aluminum Nitride for energy harvesting. The frequency (1,500–1900 Hz) off all the beams is the same, consisting of universities. Finally, the V-T beam is the most suitable for piezoelectricity.
Uddin et al. [17] a piezoelectric cantilever beam in the shape of a T has been provided and Finite Element Analysis (FEA) has been carried out on it. The mechanical characteristics, such as stress, elastic strain energy, displacement, and velocity in relation to the frequency spectrum, were established after the T-shaped cantilever beam analysis was accomplished. At the frequency of resonant vibration, the mechanical properties were determined to have their highest values. The resonance frequency of 229.25 Hz is lower than the other specified resonant frequency of the harvester which indicates that proof mass is not being utilized on the T-shaped beam.
Ashok et al. [18] designed the arrow shape of the microcantilever beam. The analysis and design of the beams were focused on enhancing the mass detection's sensitivity. All the heights, widths and lengths were calculated on a micro-scale. Analysis of the resonance frequency and mass sensitivity of this work was done by using FEM software and ANSYS. By comparing with rectangular shapes, the microcantilever beam output at zero free end width was improved by 46% and 283%.
Aamir Saud khan et al. [19] worked on an ARC shape Cantilever beam that operates on radio frequency and is utilized in the switching apparatuses. The software Intellisuite v8.7 was used for the simulation that was reported in this research, which made use of finite element modelling. The fluctuating voltage of the thickness was also improved. Based on the simulation findings, we can conclude that the smallest actuation voltage, also known as the pull-in voltage, is 1.4 V. Regarding defense and research applications, RF MEMS switches have been one of the switches with the most rapid growth. Therefore, there is a considerable amount of room for significant investigation, such as the switch's shape parameters. In the future, we will be able to continue working on improving the switching time, dependability and other aspects in order to get better overall results.
Chaudhuri et al. [20] used AC machine to generate vibration for the long-life solution to recharge the battery in Wireless Sensor Node (WSN). In this study, rectangular, tapered, perforated tapered cantilever shapes were compared. Several piezoelectric cantilever beams of the equivalent area were explored for the development of an energy harvester with a resonance frequency of 101 Hz, which is nearly comparable to the vibration of AC machines. The innovative perforated tapering structure offered has permitted for the improvement in frequency. It has been demonstrated that the proposed framework, when operated at the design frequency, generates the highest voltage output of 7.5 V, while similarly sized rectangular and tapered structures generate 0.35 and 0.8 V, respectively.
Kumar et al. [21] worked on a cantilever beam design whose shape was rectangular. In this study, the authors found the eigenfrequency of rectangular shapes and the stress measurement associated with such shapes. The structural integrity of a cantilever beam constructed from Piezoelectric Fiber Composite Bimorph (PFCB) W14 piezoelectric material was analyzed using COMSOL Multiphysics software. In order to use piezoelectric material for energy harvesting, the maximum deflection at a vibration frequency of 30.375 Hz was correlated to a higher electrical voltage supply.
Rai et al. [22] compared the output power between the conventional (Rectangular shape) and modified (E-shape) structure of the cantilever beam. The parameters (i.e. length, width and thickness) were also selected in millimeter (mm) scale. Various structures of the cantilever beam are designed by using COMSOL Multiphysics 5.1. the output voltage obtained from rectangular shapes is 0.278 V and E-shaped is 0.32 V. So, the maximum output comes from the E-shape cantilever beam.
Sarkar et al. [23] developed a spiral-shaped cantilever beam designed for a piezoelectric energy harvester. In this work, Instead of PZT-5H material, ZnO was chosen. COMSOL Multiphysics was used for building and simulated the structure. This simulation model was used for operating the pacemaker. In order to increase the pacemaker's longevity, the system is made to recharge the pacemaker's battery. The resonance frequency is obtained from human vibration. The output power is 3.5 µW and the resonant frequency was also obtained at 45.8 Hz which is reliable with the human heartbeat.
Nabavi et al. [24] built a T-shape cantilever beam on a micro-scale by using this vibration. The motive of this work is to reduce the operational frequency by 36% and the conventional energy is 4.8 times. A large quantity of stress/strain can be harvested from the tip of the T-shaped piezoelectric construction, besides the anchor region, which is analogous to the typical straight cantilever harvesters.
P.K. et al. [8], demonstrates a mathematical model cross-section of a rectangular form microcantilever beam under different stress. This work involves the measurement of natural frequency. 15–19% of the frequency does not contain any errors. In order to explain the pattern, the frequency response of a micro-cantilever beam detected using the acquired model is compared which was described in the literature for a step-up micro-cantilever beam. The created model allows for the harvesting of micro-cantilever beams using natural frequencies. The model's mass (M) and stiffness (K) matrices determine the beam's natural frequencies. These frequencies are acquired from the model. The square root of the matrix can be used to determine the workpiece's natural frequencies.
Anand et al. [25] designed a Piezoelectric (PZs) cantilever beam in the L shape developed with PZEH, which is used for appropriate low frequency. The simulation of the proposed structure was run at an acceleration of 1 g, producing a voltage of 11.6 V at a frequency of 79.5 Hz. The suggested L-shaped PZEH has an output power of 10.8 W at the frequency that corresponds to its resonant mode. There is a margin of error of not more than 5 mm in the EH measurement.
Borodich et al. [26] the AFM techniques compare the V-shape and rectangular shape cantilever beams by fundamental and numerical. The dimensions, length and width are the same. Polycarbonate materials were used to construct the models. The sheet thickness is 1 mm, 2 and 3 mm. After the comparison, the 3 mm thickness gives the 46% spring constant from V-shape.
Chaudhuri et al. [27] it is possible to identify the flaw in the cracked beam and see how it differs from the non-defective shaft through modal vibration analysis. It was discovered that the natural frequencies of the beam dropped when the size of the cracks in the beam became more extensive. It is found that the amplitudes of vibration grew as the extent of the damage became more extensive. In the event of an increased location, the natural modal frequencies also rose. This occurred because the distance between the crack and the fixed end grew. When the point of the crack was enhanced from its fixed-end position, the results showed that the amplitude at higher natural frequencies grew. In comparison, the amplitude at lower natural frequencies decreased.
An investigation into the resonance frequency response was carried out and it involved changes to the beam structure. The effect of making several different adjustments to the beam was analyzed. The findings demonstrate that resonant frequencies are influenced by modifications made to the beam. These findings can be applied to determining the appropriate dimensions for fabricating devices with particular resonant frequencies [28, 29].
ULP EH circuit investigates through this model. A mechanical trembling to transpire the piezoelectric transducer instigates the electric charge. The converter is treated for low-power to high-power (MV). The circuit is simulated in LTSPICE software. It works in standard-scale electronic devices like charging batteries, wireless sensors, bugging devices and many more MEMS. It may be enhanced by changing IC and rectified to reduce the voltage drop [30]. Gong et al. [31] Piezoelectric can be rehabilitated at low-power, which is intended for micro energy. A triple layer piezoelectric circuit is synchronized by the authors. Expanding this PZT material to perform energy harvesting and strategy for a power generator.
The summarization results with past researchers' work are given in Table 1. According to the table, the lower resonant frequency depends on the three parameters: length, width and thickness. Other shapes, for example, T-, arrow, L-, V-T, Perforated Tapered, Rectangular and E-shape have an issue with the same parameters (length, width and thickness). The generated power of these shapes is low and also the resonant frequency is high. The V-shape of the beam allows for greater flexibility and displacement, which is crucial in converting mechanical vibrations into electrical energy. When the beam is subjected to mechanical vibrations, it bends and flexes, generating a voltage across the piezoelectric material that is attached to the beam. Additionally, the V-shape allows for greater strain and stress concentration at the tip of the beam, which further enhances the piezoelectric effect. This effect is maximized when the length and thickness of the beam are properly designed to match the frequency of the mechanical vibrations.
Comparison of the various types of cantilever Shapes (with present work)
| NO | Authors name | Cantilever shape | Cantilever beam size | Resonance frequency (Hz) | Power | Applications | ||
| Length (L) | Width (W) | Thickness (T) | ||||||
| 1 | Abid Iqbal et al. (2015) | V-T | 1,225 µm | 250 µm | 1 µm | 1,560 Hz | N/A | Finite Element Analysis |
| 2 | Md Naim et al. (2016) | T | 18 mm | 8.64 mm | 0.15 mm | 229.25 Hz | 149.1 µW | Bio-medical Device |
| 3 | Akarapu Ashok et al. (2018) | Arrow | 200 µm | 40 µm | 0.96 µm | 1,224 Hz | N/A | Laser vibrometer |
| 4 | Aamir Saud Khan et al. (2017) | ARC | 300 µm | 100 µm | 1 µm | N/A | N/A | Switching device |
| 5 | Dipta Chaudhuri et al. (2017) | Perforated Tapered | 5 mm | 600 µm | 2 µm | 101 Hz | N/A | Wireless Sensor Node |
| 6 | Akash Kumar et al. (2019) | Rectangular | 132 mm | 14 mm | 1.1 mm | 30.375 Hz | N/A | Piezoelectric Fiber Composite Bimorph |
| 7 | Newton Rai et al. (2019) | E | 100 mm | 60 mm | 0.276 mm | 29.456 Hz | N/A | Low power Electronics Device |
| 8 | Ashutosh Anand et al. (2019) | Spiral | 5 mm | 5 mm | 0.85 mm | 45.8 Hz | 3.5 µW | The permitted size of a modern pacemaker |
| 9 | Sayed Fakhreddin Nabavi et al. (2019) | T | (2,100 + 500) µm | (3,100 + 500) µm | 10 µm | 269.1 Hz | 0.38 µW | self-supplied power management system |
| 10 | Mehrnoosh Damircheli et al. (2020) | V | 90 µm | 254 µm | 0.35 µm | N/A | N/A | Bimodal AFM |
| 11 | Ashutosh Anand et al. (2021) | L | 5,000 µm | 1,000 µm | 13 µm | 79.5 Hz | 10.8 µW | Wireless sensor machine monitoring system |
| 12 | Feodor M. Borodich et al. (2021) | V | 250 mm | 307 mm | 3 mm | N/A | N/A | Atomic force microscopy |
| 13 | Present work, (2023) | V | 90 mm | (20 + 20) mm | 1.5 mm | 156.19 Hz | _ | _ |
3 Problem statement
Biomedical applications devices such as pacemakers, Blood Pressure machines, smart health watches and Internet of Things (IoT) sensors are operated using batteries. Balaji et al. [32] sometimes batteries need to be replaced or recharged periodically. This is because it is a bio-hazard. To overcome the limitations, replacement of the batteries is also being developed through enhancing the energy harvesting circuit. Uddin et al. [33] mechanical vibration is one of the sources to produce electrical energy using piezoelectric material. After producing electrical energy, the maximum output voltage will gain at a low frequency using a cantilever beam structure to generate the frequency from mechanical vibration. Different types of shapes were used in previous work with the change of length, width and thickness to get the lowest resonant frequency and high electrical power. Investigate the literature review of this proposed system based on designing a V-Shape cantilever beam to get better frequency and power based on the cantilever beam's length, width and thickness. The majority of the shapes were studied. Finally, it will be noticed that V-shape cantilever beam would be the best output generator for EH.
4 Proposed block diagram
The piezoelectric based energy harvester system can be used to generate power using ambient energy for biomedical applications like pacemakers. Thanach-Issarasak et al. [34] In a traditional energy harvester, vibrations from the environment are used as input energy to produce electricity. Usually, the piezoelectric material is used to turn mechanical vibrations into electrical energy. A cantilever beam is one of the most moveable components of a structure. Its highest electrical power is found at its resonant frequency.
Figure 1 shows the completed proposed block diagram of the V-shape beam cantilever beam design, consisting of the Mechanical part and Electrical part for biomedical applications.
Proposed block diagram
Citation: International Review of Applied Sciences and Engineering 2023; 10.1556/1848.2023.00652
Proposed block diagram
Citation: International Review of Applied Sciences and Engineering 2023; 10.1556/1848.2023.00652
Proposed block diagram
Citation: International Review of Applied Sciences and Engineering 2023; 10.1556/1848.2023.00652
Mechanical part: Input Vibration energy has been supplied through the V-shape cantilever beam, which is designed by COMSOL Multiphysics software. The dimension of cantilever beams can be optimized with respect to the eigenfrequency. A PZT material has been used to convert the resonant frequency in Hz to electrical voltage in mV.
Electrical part: The obtained AC voltage (mV) of the mechanical part will be delivered to the electrical conditioning circuit. It consists of a DC rectifier circuit, DC step-up booster, voltage regulator and super capacitor. The rectifier circuit will convert the AC into DC. The step-up booster will be used to raise the voltage to the desired level. A voltage regulator is used to maintain the voltage level. The voltage regulator is needed when the vibration does not appear well so that it can supply the same voltage level to the output devices. The super capacitor is to store the generated voltage for applying biomedical applications.
5 Research methodology
Figure 2 shows the proposed flow chart diagram to implement the V-shape cantilever beam design of micro energy harvester for biomedical applications. The EH flowchart started with a survey of relevant literature focused on the concept of a piezoelectric cantilever, by examining the various shapes and dimensions, such as length, width, and thickness, of a V-shaped cantilever beam. This proposed method has been used to design the beam. The processes of complete simulation have been divided into three portions considered as: i) Pre-processing (Geometry design, Material Properties, Boundary Conditions and Mesh), ii) Solver (FEA Model in COMSOL Multiphysics) and iii) Post-processing (Plots and others). After the simulation, mechanical properties like frequency and displacements were obtained. Here if any unwanted and uncertain results exist then it will be essential to check the pre-processing portions of the solver and select a proper harvester for the next operation.
Design flow chart for the proposed Piezoelectric Energy Harvester
Citation: International Review of Applied Sciences and Engineering 2023; 10.1556/1848.2023.00652
Design flow chart for the proposed Piezoelectric Energy Harvester
Citation: International Review of Applied Sciences and Engineering 2023; 10.1556/1848.2023.00652
Design flow chart for the proposed Piezoelectric Energy Harvester
Citation: International Review of Applied Sciences and Engineering 2023; 10.1556/1848.2023.00652
An electrical conditioning circuit will be designed by LTSPICE simulation software. This circuit consists of a rectifier, boost-up converter, voltage regulator and supercapacitor. In the simulation process electrical component will be defined from the library. After the simulation, electrical properties such as Voltage, Current and frequency will be obtained. If any issues occur, then it will be required to check the electrical component from the library and select suitable components for the next operation.
After completing the both mechanical and electrical simulation processes, it will be integrated with the developed V-shape cantilever beam and the ULP EH circuit. In the hardware implementation processes, a mechanical shaker has been used for creating vibration on the developed V-shape cantilever beam and Printed Circuit Board (PCB) has been used for the electrical conditioning circuit to complete the system. The result has been found in micro Watt and used for biomedical applications.
6 Simulation and result
In Fig. 3 (mechanical part), two cross-sections of rectangular shape are used to design the V-shape cantilever beam design in COMSOL Multiphysics 5.5 version. Figure 3 represents the schematic diagram of the V-shape cantilever beam where Length = 90 mm, Width = (20 + 20) mm and Thickness = 1.5 mm.
Schematic diagram of V-shape cantilever beam
Citation: International Review of Applied Sciences and Engineering 2023; 10.1556/1848.2023.00652
Schematic diagram of V-shape cantilever beam
Citation: International Review of Applied Sciences and Engineering 2023; 10.1556/1848.2023.00652
Schematic diagram of V-shape cantilever beam
Citation: International Review of Applied Sciences and Engineering 2023; 10.1556/1848.2023.00652
Figure 4 shows the result of the eigenfrequency is 156.19 Hz and the maximum displacement is 1.2*10−9 mm. Next, the electrical part will be carried out for generating the expected output of 10 µW.
V-shape design between eigenfrequency vs Displacement
Citation: International Review of Applied Sciences and Engineering 2023; 10.1556/1848.2023.00652
V-shape design between eigenfrequency vs Displacement
Citation: International Review of Applied Sciences and Engineering 2023; 10.1556/1848.2023.00652
V-shape design between eigenfrequency vs Displacement
Citation: International Review of Applied Sciences and Engineering 2023; 10.1556/1848.2023.00652
Figure 5 shows the graph between displacements and resonance frequency. The resonance frequency which is 156.19 Hz typically shows the highest amplitude of motion (displacement) of a system and it is 8.2 × 10−9 mm in this graph.
Displacement vs Frequency graph
Citation: International Review of Applied Sciences and Engineering 2023; 10.1556/1848.2023.00652
Displacement vs Frequency graph
Citation: International Review of Applied Sciences and Engineering 2023; 10.1556/1848.2023.00652
Displacement vs Frequency graph
Citation: International Review of Applied Sciences and Engineering 2023; 10.1556/1848.2023.00652
Figure 6 the graph between displacement and arc length typically shows the relationship between the amount of displacement or deformation of a material and the corresponding increase in arc length. Arc length refers to the length of a curve in a two-dimensional plane or a three-dimensional space, and it is measured by the distance along the curve from one endpoint to the other.
Displacement vs Arc. Length graph
Citation: International Review of Applied Sciences and Engineering 2023; 10.1556/1848.2023.00652
Displacement vs Arc. Length graph
Citation: International Review of Applied Sciences and Engineering 2023; 10.1556/1848.2023.00652
Displacement vs Arc. Length graph
Citation: International Review of Applied Sciences and Engineering 2023; 10.1556/1848.2023.00652
The graph of displacement versus arc length can provide insights into the mechanical properties of a material, including its stiffness, strength, and elasticity. Generally, materials that are stiffer will require more force to achieve a given amount of displacement, and they will exhibit a more linear relationship between displacement and arc length.
7 Equation
Based on this equation, it can be shown that the resonant frequency of the energy harvester is directly proportional to the square root of the ratio of the elastic modulus to the efficient mass of the cantilever beam as well as the piezoelectric coupling coefficient. As comparison to a straight cantilever beam design, the V-shape cantilever beam design increases the effective mass of the cantilever beam, which in turn lowers the resonance frequency. Because of the design of the V-shape cantilever beam, the moment of inertia of the beam is increased, but its rigidity is decreased.
Where, F is the applied force, d is the movement distance, Δt is the generation power and P is the output power.
Where S is the sensitivity of the output voltage to the manufacturing tolerance T.
8 Conclusion
The piezoelectric based V-shape energy harvester is designed for converting mechanical vibration into electrical energy by using COMSOL Multiphysics Software. The resonant frequency of 156.19 Hz was obtained at the output of the cantilever beam. The PZT material will be utilized for transforming the obtained input resonant frequency to AC voltage (mV) at the output of the mechanical part. The ULP EH circuit will be simulated for increasing the generated AC voltage and convert into DC voltage by using LTSPICE software in the electrical part. The expected amount of power (10 µW) from the integration of the completed energy-harvester system (i.e. V-shape cantilever designed beam and development of ULP EH circuit) will be applied to the low-power biomedical pacemaker devices.
Author contributions
J.D: Conceptualization, methodology, formal analysis, writing—original draft, S.I.; supervision, resources, project administration. Both authors have read and agreed to the published version of the manuscript.
Acknowledgments
This work was supported by Faculty of Engineering, Multimedia University, Cyberjaya, Malaysia under research grant Project Code: RDTC/221039, TM R&D.
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