T-shaped Cantilever Research Articles

High-sensitivity narrow‑band T-shaped cantilever Fabry-perot acoustic sensor for photoacoustic spectroscopy

Photoacoustic spectroscopy (PAS) has been rapidly developed and applied to different detection scenarios. The acoustic pressure detection is an important part in the PAS system. In this paper, an ultrahigh sensitivity Fabry-Perot acoustic sensor with a T-shaped cantilever was proposed. To achieve the best acoustic pressure effect, the dimension of the cantilever structure was designed and optimized by finite element analysis using COMSOL Multiphysics. Simulation results showed that the sensitivity of such T-shaped cantilever was 1.5 times higher than that based on a rectangular cantilever, and the resonance frequency of T-shaped cantilever were able to modulate from 800 Hz to 1500 Hz by adjusting the multi-parameter characteristics. Experimental sensing results showed that the resonance frequency of T-shaped Fabry-Perot acoustic sensor was 1080 Hz, yielding a high sensitivity of 1.428 μm/Pa, with a signal-to-noise ratio (SNR) of 84.8 dB and a detectable pressure limit of 1.9 μPa/Hz1/2@1 kHz. We successfully used such acoustic sensor to measure acetylene (C2H2) concentration in the PAS. The sensitivity of PAS for C2H2 gas was 3.22 pm/ppm with a concentration range of 50 ppm ∼100 ppm, and the minimum detection limit was 24.91ppb.

An efficient microfluidic pressure sensing structure optimization using microcantilever integration

Microfluidic pressure sensors are extensively present in a wide range of applications such as wearable devices, drug detection, and many healthcare applications. Integrated microfluidic pressure sensors are highly desirable in many fields where it offers high sensitivity, non-toxicity, and high biocompatibility. In the present work, an integrated microfluidic pressure sensing mechanism is analyzed in a microfluidic device. The device is composed of poly dimethyl siloxane (PDMS) based material with a microcantilever of the same material integrated on one side of the microchannel. The pressure of fluid in the microchannel is measured by deflection generated on the PDMS microcantilever while the fluid is made to be drive-in. The pressure-based deflection measurement process is analyzed for different types of fluids and the geometry of microcantilevers. The designs for the microcantilevers are considered rectangular-shaped, T-shaped, and Pi-shaped cantilever. The modelling and analysis are done in the commercially available software tool COMSOL Multiphysics®. The results have shown that maximum deflection is achieved with a Pi-shaped microcantilever in fluid plasma (37.05 μm) and in water (30.98 μm) at 8000 μm/s fluid inlet velocity. This maximum deflection was found to be in cooperation with the pressure value at the channel inlet 125.1 Pa for Pi-microcantilever. The optimization is achieved for improved fluid pressure sensing with an integrated microcantilever, which reduces the device setup for fluid pressure analysis. The purpose of research and study is to control fluid pressure inside microfluidic channels, which can pave the way for efficient small setup cytometry and cell separation microfluidic devices.

Simulation design based on piezoelectric photoelectric composite energy harvester

A simulation design based on piezoelectric-photoelectric composite energy harvesters is proposed to solve the limitation that different energy harvesters can only work under certain conditions. The design of composite energy harvesting can capture sunlight and produce electrical energy and can also harvest vibrational energy in the environment to generate electricity from it. Cantilever beams with 6 different structures are simulated. The resonance frequency of the T-shaped cantilever beam is only 40 Hz, which can be used to collect vibration energy in the environment. The effect of different thicknesses of perovskite solar cells on the output performance was simulated. When the perovskite layer was 500 nm thick, the open circuit voltage could reach 1.08 V. The piezoelectric module and the photoelectric module are integrated into the energy collection circuit, which can collect vibration energy and light energy at the same time. The maximum output power may be obtained as 290 μW when the load resistance is 35 KΩ, and the output voltage at this time is 3.18 V. The structure broadens the application environment of the energy harvester and has the function of improving the output.

Energy harvester using two-phase flow conditions

Single-phase flow-induced vibration energy harvesting approaches, such as vortex-induced vibration, galloping, and flutter, have received considerable attention from researchers in recent years. However, the challenges and potential applications of multi-phase flow-induced vibration energy harvesting have rarely been explored. To bridge the research gap in the present energy harvesting studies based on two-phase flow, we investigated in detail the mechanism and potential benefits of the fluid–structure interaction between smart structures and two fluid phases (water and air) on the vibration energy harvesting performance. A piezoelectric energy harvester using air–water two-phase flow conditions is proposed for potential multifunctional applications. A T-shaped piezoelectric cantilever was used to harvest liquid sloshing energy in the proposed structure. A fluid–structure interaction containing two fluid phases (water and air) was theoretically modelled using the arbitrary Lagrangian-Eulerian technique. The experimental results showed that a prototype of the proposed structure can be used as a smart water bottle that simultaneously performs human-motion energy collection and acts as a drinking water bottle. The prototype achieved its maximum peak-to-peak voltage value (12.08 V) at 5 km/h for powering wireless IoT (Internet of Things) nodes. Furthermore, it can be used as an energy regenerative shock absorber to perform the dual functions of vibration damping and energy harvesting. Therefore, multi-phase flow-induced vibration energy harvesting shows great application potentials.

Analysis of Output Performance of a Novel Symmetrical T-Shaped Trapezoidal Micro Piezoelectric Energy Harvester Using a PZT-5H.

In recent years, low-power wireless sensors with high flexibility, portability and computing capability have been extensively applied in areas such as military, medicine and mechanical equipment condition monitoring. In this paper, a novel symmetrical T-shaped trapezoidal micro piezoelectric energy harvester (STTM-PEH) is proposed to supply energy for wireless sensors monitoring the vibrations of mechanical equipment. Firstly, the finite element model (FEM) of the STTM-PEH is established. Secondly, the modal analysis of the T-shaped trapezoidal piezoelectric cantilever beam is carried out by finite element software and its vibration modes are obtained. Additionally, the structural characteristics of the STTM-PEH and the composition of piezoelectric patches are described. Furthermore, the effects of resistance, acceleration coefficient, substrate materials and structural parameters of the output performance of the STTM-PEH are researched. The results indicate that the output power of the STTM-PEH rises first and then falls with a change in resistance, while the output voltage does not increase as resistance increases to a certain extent. Meanwhile, selecting copper as the piezoelectric material of the T-shaped trapezoidal piezoelectric cantilever beam can generate a higher energy output. Finally, how the structural parameters, including piezoelectric patch thickness, substrate thickness and cantilever head length, affect the output performance of the STTM-PEH is studied, which illustrates that the load range of the STTM-PEH can be appropriately broadened by adjusting the length of the cantilever beam head. This research is valuable for designing a novel high performance piezoelectric energy harvester.

Wave Mode Control of Cantilever Slab Structure of T-Beam Bridge with Large Aspect Ratio

The cantilever plate structure in a T-beam bridge with a large aspect ratio will cause vibration under the influence of environmental disturbance and self-stress, resulting in fatigue damage of the plate structure. Wave control based on elastic wave theory is an effective method to suppress the vibration of the cantilever plate structure in a beam bridge. Based on the classical thin plate theory and the wave control method, the active vibration control of the T-shaped cantilever plate with a large aspect ratio in the beam bridge is studied in this paper. The wave mode control strategy of structural vibration is analyzed and studied, the controller is designed, the vibration mode function of the cantilever plate is established, and the control force/sensor feedback wave control is implemented for the structure. The dynamic response of the cantilever plate before and after applying wave control force is analyzed through numerical examples. The results show that the response of the structure is intense before control, but after wave control, the structure increases damping, absorbs the energy carried by the elastic wave in the structure, weakens the sharp response, and changes the natural frequency of the structure to a certain extent.

Experimental investigation of T-shaped piezoelectric energy harvester activating coupled transverse and shear mode

During the past decade, the researchers have explored some of the valuable energy sources that are wasted if these are not being utilized like heat and vibration. These energy sources can be converted into micro electric power which is required in numerous electronic applications like wireless sensors, actuators etc. Many of researchers have been working on extracting the energy from ambient vibration because of its free availability in ambient. In the present study, the T-shaped cantilever beam is presented for harvesting energy from vibration under shear mode using PZT-5H (Lead Zirconate Titnate) piezoelectric material. Experimental analysis is conducted to obtain open circuit voltage response over frequency for all the configurations of piezoelectric energy harvester under study. The experimental results presented in this study concludes that the open circuit voltage developed under shear mode is maximum (5.26 V) and significantly equal to the voltage corresponding to bending mode (5.41 V) for T-shaped piezoelectric cantilever energy harvester when proof mass of 100 g is placed only at one end. Output voltage developed under shear mode for the T-shaped cantilever configuration with 100 g proof mass on one end is observed higher by approximately 12.87%, 5.83% and 5.17% than voltage for T-shaped energy harvester configuration with 50-50 g, 70-30 g masses and 85-15 g proof masses respectively. It is interesting to note that the output voltage under bending mode is reduced approximately by 15% and increased approximately by 80.07% under twisting mode for T-shaped piezoelectric energy harvester with 100 g proof mass at one extreme end compared to the T-shaped piezoelectric energy harvester with 100 g proof mass at center.

An extension of pseudo-3D vortex particle methods for aeroelastic interactions of thin-walled structures

The paper presents an extension of vortex particle methods (VPM) in the context of pseudo-three-dimensional (pseudo-3D) multi-slice coupled numerical model for complex aeroelastic interactions of thin-walled structures. The flow around immersed bodies is analysed using pseudo-3D VPM with boundary element discretisation. The existing coupled model performs the aeroelastic interactions of line-like flexible structures using rigid cross-sections; the deformation of the system is analysed using the natural vibration modes of beam elements. The novelty of the presented coupled model is the inclusion of 3D shell vibration modes for structural analysis within the existing framework. The structural equations are formulated at the mid-surface of the thin shell elements and solved in the modal coordinate system. The slice-wise pressures on surface panels are projected to the corresponding structural nodes. New positions and velocity of surface panels are calculated to satisfy the velocity boundary conditions for solving new surface vortex streets. The coupled method has been validated by identifying the critical flutter wind speed of a T-shaped cantilever system. Benchmarks aeroelastic flapping of different flexible plates are studied further. The vortex-induced vibration of a circular pipe and the ovalling oscillations in circular shells are simulated to show the applicability of the method. Finally, the aeroelastic response of a cantilever roof system is analysed under different incoming wind speeds.

An experimental validation of a new shape optimization technique for piezoelectric harvesting cantilever beams

The piezoelectric energy harvester efficiency depends on optimizing the cantilever geometry and tuning its natural frequency with vibration source frequency. Moreover, the effect of harvester parameters on natural frequency is vital in tuning the resonance frequency. So, a COMSOL Multi-physics finite element analysis, Eigen frequency study and analytical analysis using MATLAB were constructed to calculate the resonance frequencies and to analyze the harvester parameters effect. Five harvester different shapes, namely, the T-shaped, rectangular, L-shaped, variable width, and triangular cantilevers were optimized using the genetic algorithm. The simulation of the five shapes was implemented using COMSOL. The results indicated that the T- shaped cantilever produced the largest power. Due to its high power and inclusive shape, the T-shaped cantilever with variable width was optimized using the COMSOL optimization module (BOBYQA). Linking genetic algorithm and COMSOL optimization module has highly improved the output power. The COMSOL results were validated using an experimental setup of piezoelectric cantilevers. The experimental setup was employed to calculate the voltage of the base excited harvester with very low excitation frequencies from 0.5 to 10 Hz. Also, the experimental setup investigated the effect of the tip mass, length of the cantilever, and piezoelectric material volume on the output voltage.

Measurement of the Poisson’s ratio and Young’s modulus of an isotropic material with T-shape contact resonance atomic force microscopy

The Poisson’s ratio and the Young’s modulus play an important role in the characterization of nanomaterial mechanical properties. They are the vital parameters of understanding nanoscale material behavior. Here we report a method of quantitatively determining the values of the Poisson’s ratio and the Young’s modulus with a T-shape contact resonance atomic force microscopy. Unlike the cantilever of a traditional atomic force microscopy, the flexural and torsional modes of the T-shape cantilever are simultaneously excited and coupled in the contact mode. Through the analysis, the bifurcation of the coupled contact resonance frequencies is found in higher modes with the increasing contact stiffness. More importantly, the frequency bifurcation point can be used to decouple the Poisson’s ratio and the Young’s modulus, which leads to the determination of their separate values. In contrast to the previous methods, in which the Poisson’s ratio and the Young’s modulus are intrinsically coupled and there is no effective way of decoupling, the method presented in this study offers a new way of decoupling and determining these two parameters. This efficient and accurate method can be of significant help to the characterization of various nanomaterials.

T-Shaped Piezoelectric Structure for High-Performance MEMS Vibration Energy Harvesting

In the recent decades energy harvesting from ambient vibration by the micro-electromechanical systems (MEMS) has been recognized as a promising solution to boosting lifespan of low-power electronic devices. Apparently, highly efficient MEMS vibration harvesters with lower operational frequencies are advantageous. In this paper we propose a new mechanical structure to aim for energy conversion efficiency enhancement and operational frequency reduction for the piezoelectric MEMS vibration energy harvesters. The proposed structure has a T-shaped geometry with integration of two identical proof masses at the T-segment. Thanks to two degrees-of-freedom, in this structure both bending and torsional mode frequencies can be located close to each other. Its analytic model of frequency response is derived and then validated by finite element modeling (FEM) simulations and prototype measurements. Compared to the conventional straight cantilever configuration, our proposed T-shaped piezoelectric cantilever structure can help distribute mechanical strain in broader areas with higher magnitude and lower resonant frequency. Our analytical, numerical, and experimental studies show that the normalized power density of the proposed T-shaped harvester is 4.8 times higher than that of the conventional one, in addition to 36% resonant frequency reduction. [2019-0146]

DBR Fiber Laser Based High-Resolution Accelerometer Network

In this paper, we report a high-resolution and precision acceleration sensor network with potential large sensing capacity, which is based on distributed Bragg reflector fiber lasers. To start with, a transducer based on a T-shaped cantilever beam and an adjustable bearing is theoretically designed and experimentally employed to achieve high sensitivity and wideband frequency response. Second, the beat frequency interrogation system that utilizes super-heterodyne receiver and digital orthogonal phase identifying technology is developed to improve the resolution of the sensors. In addition, assisted with the wavelength/time division multiplexing technology, hundreds of sensing units could be potentially multiplexed in the prototype system. A proof-of-concept sensing network with three acceleration sensor units is established for experimental validation. The sensor network demonstrates a sensitivity of 1.16064 GHz/g with a flat frequency response region from 20 to 200 Hz, corresponding to a noise equivalent acceleration of 17.99 ng/√Hz at 90 Hz. In particular, the measurement precision of the prototype system has been calibrated as high as 1.305 μg. The proposed acceleration sensor network could benefit potential applications in smart unmanned platforms and seismic monitoring.

Reduced order derivation of the two-dimensional band structure of a mixed-mode resonator array

In this paper, the 2D band structure of a mixed-mode metamaterial resonator array for in-plane waves is investigated. The band structure in the interior and on the boundary of the irreducible Brillouin zone and 1D dispersion diagrams for different propagation angles are calculated numerically and presented. Additionally, a reduced order analytical method is established to compare and approximate the band structure. The studied metamaterial, with a T-shaped cantilever beam as the resonator in its square array repeating unit cells, exhibits branches with mixed P and SV waves except at exactly one angle of propagation. This paper also reports on the occurrence of avoided level crossings, which are related to the existence of exceptional points in the complex domain. A reduced order analytical approach is used that can generate partial (low branches) band structure with relatively little computational effort. The reduced order model agrees well with the numerical results for these low branches and can provide support in mode identification and band sorting. With proper adjustments in parameters, this analytical method will be applicable to other metamaterials that have a similar unit cell structure.

Energy harvesting utilizing reciprocating flow-induced torsional vibration on a T-shaped cantilever beam

This paper proposes a T-shaped cantilever energy harvester powered by flow-induced torsional vibration. To collect and convert the mechanical (kinetic) energy into electric power, a pair of symmetrical acrylic cylindrical bluff bodies were installed onto the bottom surface of the T-shaped cantilever beam, one at each end; There is also one patch of Macro Fibre Composite (MFC) used as an energy collector and converter which was attached to the fixed end of the cantilever beam. This proposed setup of the energy harvester is able to generate sustainable electric power by harvesting natural mechanical power resulted from the torsional vibration of the beam due to fluid’s vortex shedding effects. The proposed energy harvester has the novelty in that our approach harvests fluid flow’s energy in a reciprocal fashion making full use of renewable energy incurred in areas surrounding the two bluff bodies. Both the theoretical and experimental analyses on the proposed energy harvesting structure were performed and demonstrated in this paper. The case in the test rig we studied on the proposed energy harvester was able to generate sustainable electric power of approximately 1.0 μW when flow speed was measured to be 0.33 m s−1 flowing through two bluff bodies each of 29.5 mm diameter. This work also looks into and discusses pros and cons of various scenarios in terms of structural geometric variations for system optimization of the proposed energy harvester.

Fabrication of MEMS cantilever using laser micromachine

This paper presents the fabrication of MEMS cantilever using laser micromachine. This technique of micromachining is able to overcome the problem limitations of conventional lithography. It also facilitates three-dimensional (3D) microfabrication rather than two dimensional (2D) microfabrication of conventional lithography. Prior to fabrication process, wet etching process using KOH solution are carried out on silicon wafer. Etching process is necessary to thin the silicon wafer for the laser micromachine purpose. The etch performance on silicon wafer was investigated by varying the concentration of potassium hydroxide (KOH) solution with respect to time. It can be seen that with higher KOH concentration and higher KOH solution temperature, the etch rate is higher and it will thin the silicon wafer faster. Even though it is beneficial when the time taken for the etching process is faster, this also resulted in a rougher wafer surface. The optimized etch rate is approximately l μm/min which yield in low surface roughness. The optimized parameters of laser micromachining were implemented to produce MEMS cantilever. Silicon wafer is used because most of the MEMS devices are silicon-based substrate. Three types of microcantilever were fabricated using laser micromachine namely rectangular cantilever, T-shaped cantilever and triangular microcantilever. Scanning electron microscope (SEM) and high power microscope (HPM) were used to obtain the surface morphology on the ablated area of the microcantilevers.

A Novel Fiber Bragg Grating Displacement Sensor With a Sub-Micrometer Resolution

This letter has proposed a novel fiber Bragg grating (FBG) displacement sensor with a sub-micrometer resolution through the use of the transverse property of a suspended optical fiber with a pre-tension force. A wedge-shaped sliding block and a T-shaped cantilever beam formed a conversion mechanism to transfer the horizontal measured-displacement into the transverse movement of the optical fiber midpoint. Compared with existing FBG displacement sensors, this design does not only avoid the FBG-pasting process and its associated issues, such as the chirping failure and low repeatability, but also achieves a high resolution. The sensing principle has been presented, and the corresponding theoretical model has been derived and validated. Experiments show that this design has an excellent sensitivity of 2086.27 pm/mm and a high resolution of $0.48~\mu \text{m}$ within a range of 1.0~2.0 mm. The displacement results from the proposed sensor closely agree with the values detected from the commercial laser displacement sensor, validating its effectiveness. Therefore, the proposed sensor can be directly utilized to measure the sub-micrometer displacement, and also support multi-point distributed detection.

Shaking table tests on the seismic performance of a flexible wall retaining EPS composite soil

A series of shaking table tests were designed and conducted to study the seismic performance of an inverted T-shape cantilever retaining wall with an anti-sliding tooth at the base using EPS composite soil as backfills. For comparison, the same wall model retaining Nanjing fine sand was simultaneously excited. The macro phenomena and seismic behaviors of two wall–soil systems are depicted in detail and analyzed. The displacement mode of the non-sliding flexible retaining wall and distribution characteristics of dynamic earth pressure acting on the wall back retaining two types of backfills are emphasized. The testing results show that, as a kind of backfill, Nanjing fine sand has a greater peak ground acceleration (PGA) than EPS composite soil under the kinematic interaction between wall and soil, while the difference in the inertial force of the retaining wall itself is not obvious. As the input peak base acceleration increases, Nanjing fine sand which possesses the compaction strength gradually transforms from the global shearing deformation to the wedge sliding deformation, while EPS composite soil with a cemented strength exhibits the block shearing deformation mode under all excitations. The tested retaining walls with the rotation displacement are non-sliding flexible walls. The dynamic deformation mode of backfills is closely related to the inertial interaction between wall and soil, which results in a significant difference in the dynamic earth pressure increment distribution between the walls retaining two types of backfills. The dynamic earth thrust in the retaining wall-Nanjing fine sand system (WSS) has a nonlinear relation with PGA, and the action position approximated 2/3 wall height. A linear relation is more suitable for retaining EPS composite soil and the corresponding action position is about 1/3 wall height. The retaining wall-EPS composite soil system is shown to have a better seismic performance in contrast to WSS. The Seed and Whitman method with 100% PGA is recommended to predict the dynamic earth thrust on the wall retaining EPS composite soil.

Numerical simulations of aeroelastic instabilities to optimize the performance of flutter-based electromagnetic energy harvesters

The article presents a two-dimensional fully coupled fluid–structure interaction model for simulating aeroelastic instabilities to evaluate and optimize the performance of flutter-based electromagnetic energy harvesters. The flutter-type unstable vibration of T-shaped cantilever systems is investigated as a driving mechanism for small-scale energy conversion. A flow solver based on the vortex particle method and a structural solver based on a corotational finite element formulation are coupled in order to accurately account for the geometrically nonlinear effects of such very flexible elements. A reference harvester is simulated considering the damping effects arising from the electromagnetic transducer. The estimated flutter wind speed and the predicted energy outputs under different electrical resistances are found to agree reasonably well with reference wind tunnel experiments. The influence of physical parameters such as length, thickness, and cantilever tip height on the performance of the harvester is investigated up to an envelope volume of 42 cm3. The maximum power output is found to be 5.3 mW at 8 m/s. The optimized harvester shows a better performance under low wind speeds by producing 0.65 mW at 4 m/s where the reference harvester produced no power.

Dynamic Detection of PPG(Photo Plethysmography) Signals Using Mems Self Designed Sensors

Objectives: To design Micro Electro Mechanical System (MEMS) based sensor with novel design considerations to detect/ identify PhotoPlethysmography(PPG) signals when the person is in dynamic mode. To simulate the above design using COMSOL Multiphysics and evaluate the results with the existing methodologies. Methods/Statistical Analysis: A MEMS based sensor with a four T-shaped cantilever with middle load hanged structure is designed in COMSOL Multiphysics and after attaining the required resonant frequency of PPG, by using capacitive actuation technique the acquired mechanical signals are evaluated and digitised. Findings: PPG sensors optically recognize changes in tidal volume of blood (i.e., changes in the force of light perceived) in the vascular bed of little scale tissue by reflection from or transmission through the tissue. If the person is in static mode it is very easy to detect blood flow rate. If suppose the person is not in rest, i.e., may be dynamic we will observe many variations in blood flow rate. So it is very difficult to estimate the blood flow rate. This Patch type device easily measures the blood flow rate. Application/Improvements: Mainly these type of devices are useful to detect variations in blood flow rate in human whether in static condition or in dynamic condition. In future we are planning to develop implantable sensors with reporting system to doctor in particular intervals of time. This may be helpful to doctors to cater the needs of human society at right time whenever it is needed

Energy conversion by ‘T-shaped’ cantilever type electromagnetic vibration based micro power generator from low frequency vibration sources

The design, development, and analyses of low-frequency vibration based T-shaped cantilever type electromagnetic micro power generators (EVMPGs) are presented in this paper. Four different configurations (Configurations A to D) of EVMPGs were designed and fabricated and subsequently characterized using detailed experimental and limited analytical techniques. Configuration A and B consisted of a single and a double cylindrical moving magnets (NdFeB), respectively, while Configuration C consisted of four rectangular moving magnets with respect to a fixed copper coil. In contrast, Configuration D used a moving coil between four rectangular magnets with a back-iron bar. The open circuit RMS voltage output was observed to be a maximum from Configuration D (98.2mV at 6.29Hz) with a base vibration acceleration of 0.8ms−2. Therefore, Configuration D was selected for further experimental investigations, which included changing the back-iron bar thickness, changing the base acceleration level, and changing the air gap separation between the magnets in order to optimize this configuration. The maximum load RMS voltage and power outputs of Configuration D were 105.4mV and 1.35mW at 6.29Hz for load resistance 8.2Ω and a base acceleration of 0.8ms−2 with a 4.2mm back-iron bar when the air gap between the magnets was 20mm. Finally, a small portable EVMPG prototype was developed based on the Configuration D and was tested at different human movement conditions (i.e., walking, quick walking, and running). The developed EVMPG prototype was capable of harvesting 35.2mV and 0.22mW at 7Hz with load resistance 5.6Ω for a base acceleration of 0.8ms−2.