Piezoresistive Accelerometer Research Articles

High-Temperature SiC Piezoresistive Accelerometer Fabricated by Femtosecond Laser

High-Temperature SiC Piezoresistive Accelerometer Fabricated by Femtosecond Laser

Ultra-high-sensitivity micro-accelerometer achieved by pure axial deformation of piezoresistive beams

Microfabricated piezoresistive accelerometers with purely axially deformed piezoresistive beams have demonstrated high performance. However, the conventional design of such accelerometers requires complex theoretical calculations and specific dimensional conditions to achieve purely axial deformation, which inevitably increases the difficulty and cost of the design and manufacturing. We propose an innovative structure that can simply realize pure axial deformation of piezoresistive beams by eliminating the transverse displacement at both ends without tedious calculations. An accelerometer based on the structure was fabricated; both static and dynamic performances were tested. The results showed that the accelerometer had high sensitivity (2.44 mV g−1 with 5 V bias, without circuit amplification), low cross-axis sensitivity (1.56% and 0.49 %, respectively), and high natural frequency (11.4 kHz), with a measurement range of 0–100 g. This design method provides an easy approach for designing high-performance piezoresistive sensors.

Development of a High-Performance Microaccelerometer With Position Independent Pure-Axial Stressed Piezoresistive Beams

It has been demonstrated that piezoresistive beams in a purely axial deformation state significantly enhance the performance of piezoresistive accelerometer. Current solution to realize purely axial deformation of piezoresistive beams for high performance micro-accelerometer relies heavily on beam positions, which limits its design flexibility and the error tolerance in the fabrication process. In this paper, a novel structure with position independent pure axially deformed piezoresistive beams is proposed. By controlling synchronous displacements at both ends of piezoresistive beams, the pure axially stress states of the piezoresistive beams can be easily realized at any beam position without tedious theoretical calculations. The theoretical model was developed to understand the relationship between the displacement and the axial stress of the piezoresistive beams, as well as the natural frequency of the whole structure. Then, the correctness of the theoretical model was verified by finite element simulation and experiments. The results demonstrated that the accelerometer had an extremely high sensitivity of 2.44 mV/g/5 V (without circuit amplification), and a high natural frequency of 11.4 kHz.

Design of a Biaxial High-G Piezoresistive Accelerometer with a Tension-Compression Structure.

To meet the measurement needs of multidimensional high-g acceleration in fields such as weapon penetration, aerospace, and explosive shock, a biaxial piezoresistive accelerometer incorporating tension-compression is meticulously designed. This study begins by thoroughly examining the tension-compression measurement mechanism and designing the sensor's sensitive structure. A signal test circuit is developed to effectively mitigate cross-interference, taking into account the stress variation characteristics of the cantilever beam. Subsequently, the signal test circuit of anti-cross-interference is designed according to the stress variation characteristics of the cantilever beam. Next, the finite element method is applied to analyze the structure and obtain the performance indices of the range, vibration modes, and sensitivity of the sensor. Finally, the process flow and packaging scheme of the chip are analyzed. The results show that the sensor has a full range of 200,000 g, a sensitivity of 1.39 µV/g in the X direction and 1.42 µV/g in the Y direction, and natural frequencies of 509.8 kHz and 510.2 kHz in the X and Y directions, respectively.

Microleverage Mechanism Assisted Novel Biaxial Piezoresistive Micro Accelerometer With Improved Sensitivity

A novel structure was presented for a microelectromechanical system (MEMS) piezoresistive accelerometer. Taking advantage of the effects of tiny piezoresistive beam (TPB) to generate stress concentration region and microleverage mechanism to amplify the force, a piezoresistive accelerometer was proposed with improved sensitivity. The measured sensitivity was determined by the amplified inertia force applied to the TPBs. Based on the model analyses, the force amplification factor was influenced by the beams’ spring constants and the distance between support beam and TPB. The simulations were further carried out to verify the effects of amplifying force and find out the effects of dimensional parameters on amplification factor. The results suggested that the amplification factor was influenced by support and hinge beam widths dramatically, and also affected by the distance between support beam and TPB. Based on the simulation findings, three prototypes (denoted as XJTU_11, XJTU_12 and XJTU_32) were proposed with different support and hinge beam widths along with the distance between support beam and TPB to verify the amplification effect. Furthermore, the prototypes were successfully fabricated by MEMS technology with a size of 4.4 mm × 4.4 mm and packaged for experimental tests. The sensitivities were determined to be 1.03 mV/g/5V, 0.871 mV/g/5V and 0.736 mV/g/5V for XJTU_11, XJTU_12 and XJTU_32, respectively. The sensitivity of XJTU_11 increased by 18.4% and 40.1% compared with XJTU_12 and XJTU_32 respectively. The results indicated that the higher amplification factor was beneficial to the device to obtain the higher sensitivity. The figure of merit showed that proposed accelerometer obtained a more favorable comprehensive performance. This new design provided a good strategy and revealed the promising potential in improving the accelerometer’s sensitivity.

Monolithically integrated triaxial high-performance micro accelerometers with position-independent pure axial stressed piezoresistive beams

With the increasing demand for multidirectional vibration measurements, traditional triaxial accelerometers cannot achieve vibration measurements with high sensitivity, high natural frequency, and low cross-sensitivity simultaneously. Moreover, for piezoresistive accelerometers, achieving pure axial deformation of the piezoresistive beam can greatly improve performance, but it requires the piezoresistive beam to be located in a specific position, which inevitably makes the design more complex and limits the performance improvement. Here, a monolithically integrated triaxial high-performance accelerometer with pure axial stress piezoresistive beams was designed, fabricated, and tested. By controlling synchronous displacements at both piezoresistive beam ends, the pure axial stress states of the piezoresistive beams could be easily achieved with position independence without tedious calculations. The measurement unit for the z-axis acceleration was innovatively designed as an interlocking proof mass structure to ensure a full Wheatstone bridge for sensitivity improvement. The pure axial stress state of the piezoresistive beams and low cross-sensitivity of all three units were verified by the finite element method (FEM). The triaxial accelerometer was fabricated and tested. Results showing extremely high sensitivities (x axis: 2.43 mV/g/5 V; y axis: 2.44 mv/g/5 V; z axis: 2.41 mV/g/5 V (without amplification by signal conditioning circuit)) and high natural frequencies (x/y axes: 11.4 kHz; z-axis: 13.2 kHz) were obtained. The approach of this paper makes it simple to design and obtain high-performance piezoresistive accelerometers.

Design and Experiment of a Hybrid-Integrated Ultrahigh-g Accelerometer With Variable-Section Beam

Due to the special fields of aerospace, explosion impact, weapon penetration and other high g value acceleration test, the sensor test range and anti-overload capability have great requirements. At present, most accelerometer beams with equal section are used. The existing data prove that the beam structure with variable section can effectively solve the problem of stress concentration, improve the anti-overload capability of acceleration sensor, and increase the system stability through theoretical simulation. This study presents a hybrid-integrated high-precision MEMS ultra-high-g piezoresistive accelerometer, which is composed of a sensitive structure and an ASIC interface (application specific integrated circuit). Based on the traditional constant-section four-beam accelerometer, a variable-section beam is proposed, and the section size increases linearly with the length of beam. Through finite element simulation analysis, it is verified that the variable section beam has the characteristics of reducing stress concentration and can improve the anti-overload ability of the accelerometer. The simulation results show that the maximum stress of the structure under 200,000 g is 28.34 MPa, and its resonance frequency is 548 kHz. Finally, the processing flow is designed, and the fabrication of MEMS chip is completed. Based on the TSMC 0.35 μm process, the ASIC interface is designed and fabricated to process the signal from the sensing element and realize the functions of amplification and filtering. The MEMS chip and ASIC chip are integrated by gold wire bonding, packaged in a stainless-steel shell, and tested by Hopkinson bar. The test results show that the sensitivity of the accelerometer is 0.2747 μV/g, the non-linearity is 2.79%, and the full range is 200,000 g, and the anti-overload capacity is 250,000 g.

Modeling and Characterization of a Novel In-Plane Dual-Axis MEMS Accelerometer Based on Self-Support Piezoresistive Beam

Herein, a novel in-plane dual-axis micro-electro-mechanical system piezoresistive accelerometer was proposed based on theoretical and simulation analyses. Its self-support piezoresistive beam (SPB) possessed the features of force amplification and axial deformation to obtain high sensitivity. To clarify the influence of structural dimensions on the performance of the accelerometer and the pure axial-deformation condition of the SPB, a theoretical model was established to analyze mechanical behavior. The theoretical results were in well accordance with the simulation ones, displaying a maximum relative error of less than 10%. The theoretical and simulation results suggested that the accelerometer with thin and long support/hinge beams possesses a higher sensitivity but a lower frequency. However, the sensitivity and natural frequency increased simultaneously before the distance between SPB and support beam <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D$ </tex-math></inline-formula> reached a certain value. The simulated longitudinal stress of SPB achieved the average value of 32.473 MPa, and the first-order natural frequency was nearly 13.6 kHz. Furthermore, the fabricated accelerometer was tested in a simple packaging case. The experimental results demonstrated that the proposed accelerometer had a measuring sensitivity of 0.198 mV/g/V with a maximum non-linearity of 1.00% FS and a resonant frequency of 12.93 kHz. The cross sensitivities were 11.93 and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$15.97~\mu \text{V}$ </tex-math></inline-formula> /g/5V in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$y$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$z$ </tex-math></inline-formula> axes, respectively, which were 1.21% and 1.61% of the prime-axis sensitivity. The zero offset with varying temperatures was 0.00296%/°C, and the zero drift in the long-term static stability test was 0.02 mV. All the results above revealed the promising application potential of the proposed accelerometer in vibration detection in the high-speed rotating spindle of machine tools. [2022-0057]

Design and Implementation of a Novel Membrane-Island Structured MEMS Accelerometer With an Ultra-High Range

Antioverload high-range accelerometer is playing an increasingly important role in the field of hard target penetration testing, and the demand of higher accuracy and higher range accelerometers is growing consequently. Therefore, a novel accelerometer with a new structure of membrane island is proposed in this article, while the measurement range is significantly improved to 200 000 g. The design is mainly based on the finite-element method. In general, the membrane-island structured piezoresistive accelerometer is formed of a four-clamped membrane that carries a piezoresistor at the four ends. The four piezoresistors form a Wheatstone bridge. Then, based on the Timoshenko plate and shell theory, a mathematical stiffness model of the four-clamped membrane is established. The detailed parameters of the sensor are carried out by the finite-element analysis (FEA) and optimization, and it has a maximum stress of 26.8 MPa and a maximum displacement of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.208~\mu \text{m}$ </tex-math></inline-formula> when applying an input acceleration of 200 000 g. Finally, the sensitivity test, antioverload test, and dynamic test of three membrane-island structured prototypes are carried out, and their sensitivities are 0.579, 0.505, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.532~\mu \text{V}$ </tex-math></inline-formula> /g, respectively; the passband with 5% dynamic error is 14.9, 16.5, and 15.8 kHz, respectively. The accelerometer has an antioverload capability of 250 000 g, which is verified by the Hopkinson bar. The test results show that this membrane-island structured accelerometer has both good antioverload capability and high accuracy.

Study on stress isolation structure of piezoresistive high-g accelerometer

We put forward a novel thermal stress isolation structure with five anchors, which greatly suppresses the zero offset of piezoresistive high-g accelerometer. In this paper, the parameters of the thermal stress isolation structure are optimized by finite element simulation to ensure that the sensor has lower zero offset and a good natural frequency. A high natural frequency can prevent the sensor from being damaged due to resonance when it is subjected to shock. Finally, the zero offset of the sensor with thermal stress isolation is reduced to 10% of that without thermal stress isolation. Natural frequency of the sensor is 264.18 kHz. Its sensitivity is 1.1μV/G/5V according to shock simulation of 100,000 g.

Theoretical and numerical investigation of a new 3-axis SU-8 MEMS piezoresistive accelerometer

This paper investigates the static and dynamic performances of a new enhanced design of 3-axis MEMS polymer piezoresistive accelerometer. Its key geometric parameters are optimized using a developed numerical finite element model (FEM). Using FEM analysis, the evaluated induced stress fields show a clear improvement compared to two similar silicon-based designs found in literature. Under 100 g z-axis accelerations, the proposed design proof-mass deflection is 21.78 μm and the maximum induced stress in the beams is 13.2 MPa. With the incorporation of SU-8/Carbon Black (CB) piezoresistive layers in locations of maximum induced stress, the piezoresistive analysis is performed to deduce the variations in resistance values. Using FEM dynamic analysis, the Eigenfrequency is 1.08 kHz and the quality factor is 5.55. In addition, a complete analytical model is developed and we show that values from derived expressions are in good agreement with results obtained from FEM simulations. The details of a low-cost and simple fabrication process-flow is provided for the proposed design.

High Sensitivity MEMS Accelerometer Using PZT-Based Four L-Shaped Beam Structure

Piezoelectric accelerometers present higher sensitivities and better signal-to-noise ratios in comparison with piezoresistive and capacitive accelerometers. A micro-electromechanical system (MEMS) piezoelectric accelerometer was designed and manufactured with four L-shaped beams covered by Lead Zirconate Titanate (PZT) thin film with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1~\mu \text{m}$ </tex-math></inline-formula> in thickness which was deposited using sol-gel methods. The micro devices, whose size and the optimized PZT distribution were determined by theoretical and simulation analysis, were fabricated on the silicon substrate using PZT films working in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${d}_{31}$ </tex-math></inline-formula> mode. Different from the conventional vertical crossbeam accelerometers, the designed structure devotes to the larger area piezoelectric film laid on L-shaped supporting beams with higher energy transferring efficiency for sensing. Then the chips of accelerometer were fabricated, and the proposed sensor was packaged on the printed circuit board (PCB). In addition, the microsphere was integrated in the center of the beams. Finally, the properties of the accelerometer were measured by vibration measurement system. The measuring results show that the initial sensitivity of the accelerometer is 28.14mV/g at 500Hz. The proposed piezoelectric accelerometer has high sensitivity and low resonance frequency, and the frequency response on each beam is consistent, providing a new structure for high-performance accelerometer.

Simulation Analysis and Fabrication of a Silicon Carbide-Based Piezoresistive Accelerometer

This paper proposes a Micro Electro Mechanical Systems piezoresistive accelerometer based on a whole SiC substrate. Compared with Si-based sensors, SiC-based sensors have stronger mechanical advantages and unique advantages for applications in ultra-high temperature environments. The characteristics of the accelerometer are designed and numerically simulated, and the accelerometer is evaluated in terms of stress load and working frequency band. An innovative design is carried out to eliminate the stress concentration phenomenon in the corner area of the sensor, which guarantees the working safety of the fragile structure of SiC. After fabrication, packaging and vibration experiment, it is found that the sensor’s working sensitivity can reach 0.21mv/g, and its linearity can reach 98%.

Fabrication and Performance of a Bulk 4h-Sic Mems Piezoresistive Accelerometer

Fabrication and Performance of a Bulk 4h-Sic Mems Piezoresistive Accelerometer

Single‐Process 3D‐Printed Triaxial Accelerometer

AbstractFor thermoplastic material extrusion 3D‐printing functional filaments with electrically conductive, piezoresistive, piezoelectric, capacitive or magnetic properties are developed. The functional filaments result in piezoresisitve static/quasi‐static sensors; however, these 3D‐printed sensors are manufactured in several processes, for example, the creation of highly conductive paths using embedded copper wires or by silver inking. The multi‐process 3D printing of sensors presents an obstacle to smart functional 3D‐printed structures where the sensory element is in situ printed at the location and orientation of use, including the electrical paths. This research introduces a three axial piezoresistive accelerometer where the whole sensor, including highly conductive electrical paths, is printed in the same process of thermoplastic material extrusion. The structural components of the sensor are printed with a non‐conductive polylactide material, the sensory element with a conductive material that has a relatively high resistivity, and the electrical paths with a conductive material that has a relatively low resistivity. As discussed in the manuscript with single‐process sensors, the functional tuning of sensors is as easy as changing the design. The design and manufacturing solutions researched for the triaxial accelerometer can be applied to other 3D‐printed sensors, for example, force sensors and opens up the possibility of a single‐process 3D‐printed smart structure.

Fabrication and characterization of a bulk micromachined polysilicon piezoresistive accelerometer

This paper presents the fabrication and characterization of a MEMS bulk micromachined piezoresistive accelerometer. For transduction of acceleration into output voltage, polysilicon piezoresistors are used. Due to cost effectiveness, polysilicon piezoresistors are preferred over SOI-based silicon piezoresistors. The accelerometer is designed using FEM-based MEMSCAD tool CoventorWare®. The accelerometer sensor is realized using a hybrid approach, consisting of wet and dry bulk micromachining techniques. The developed sensor is characterized for static and dynamic performance using nano-indenter and electrodynamic shaker, respectively. From static characterization, stiffness and natural frequency are found to be 7.25 kN/m and 6.78 kHz, respectively. From dynamic characterization, bandwidth and sensitivity are found to be 475 Hz and 10 mV/V/g, respectively.

Monitoring of Sitting Postures With Sensor Networks in Controlled and Free-living Environments: Systematic Review.

A majority of employees in the industrial world spend most of their working time in a seated position. Monitoring sitting postures can provide insights into the underlying causes of occupational discomforts such as low back pain. This study focuses on the technologies and algorithms used to classify sitting postures on a chair with respect to spine and limb movements, using sensors and wearables such as inertial measurement units, pressure or piezoresistive sensors, accelerometers or gyroscopes, combined with machine learning approaches. A total of three electronic literature databases were surveyed to identify studies classifying sitting postures in adults. Quality appraisal was performed to extract critical details and assess biases in the shortlisted papers. A total of 14 papers were shortlisted from 952 papers obtained after a systematic search. The majority of the studies used pressure sensors to measure sitting postures, whereas neural networks were the most frequently used approaches for classification tasks in this context. Only 2 studies were performed in a free-living environment. Most studies presented ethical and methodological shortcomings. Moreover, the findings indicate that the strategic placement of sensors can lead to better performance and lower costs. The included studies differed in various aspects of design and analysis. The majority of studies were rated as medium quality according to our assessment. Our study suggests that future work for posture classification can benefit from using inertial measurement unit sensors, since they make it possible to differentiate among spine movements and similar postures, considering transitional movements between postures, and using three-dimensional cameras to annotate the data for ground truth. Finally, comparing such studies is challenging, as there are no standard definitions of sitting postures that could be used for classification. In addition, this study identifies five basic sitting postures along with different combinations of limb and spine movements to help guide future research efforts.

Calibration Analysis of High-G MEMS Accelerometer Sensor Based on Wavelet and Wavelet Packet Denoising.

High-G accelerometers are mainly used for motion measurement in some special fields, such as projectile penetration and aerospace equipment. This paper mainly explores the wavelet threshold denoising and wavelet packet threshold denoising in wavelet analysis, which is more suitable for high-G piezoresistive accelerometers. In this paper, adaptive decomposition and Shannon entropy criterion are used to find the optimal decomposition layer and optimal tree. Both methods use the Stein unbiased likelihood estimation method for soft threshold denoising. Through numerical simulation and Machete hammer test, the wavelet threshold denoising is more suitable for the dynamic calibration of a high-G accelerometer. The wavelet packet threshold denoising is more suitable for the parameter extraction of the oscillation phase.

Design principles for a single-process 3d-printed accelerometer – theory and experiment

Fused-filament fabrication, one of the most accessible additive manufacturing technology, has already been used to manufacture piezoresistive static/quasistatic strain sensors, force sensors and wind sensors. Recent research showed that fused-filament fabrication could also be used for the manufacturing of dynamic sensors. However, the anisotropic mechanical and piezoresistive behaviour, the heterogeneity, the large number of process parameters and the large number of possible geometrical designs open up numerous design options for manufacturing. Additionally, a small size is difficult to achieve due to the relatively low geometrical tolerances and the resolution of fused-filament fabrication. This paper is focused on the design principles of a single-process, fused-filament fabricated, uni-axial accelerometer with a piezoresistive sensing element. The anisotropic piezoresistive behaviour is researched for the maximum sensitivity in the measured acceleration direction and the minimal cross-axis sensitivity for the perpendicular axes. The analytical accelerometer model is based on a Bernoulli-Euler beam and is used to understand the frequency and the geometrical influences of the piezoresistive accelerometer with a beam-shaped sensing element and an attached intertial mass. Finally, a small-sized (22 × 22 × 15 mm3), single-axis, prototype accelerometer, with an approximately linear response up to-425 Hz and a low cross-axis sensitivity was manufactured. The derived principles can be used for further optimisation of the developed prototype sensor and as a foundation for the derivation of design principles for other types of fused-filament fabricated accelerometers, including 3-axis accelerometers. keyword: accelerometer; piezoresistivity; additive manufacturing; fused filament fabrication; dynamic sensor; 3D printing.

Novel high-performance piezoresistive shock accelerometer for ultra-high-g measurement utilizing self-support sensing beams.

This study describes the design and implementation of a novel high-performance piezoresistive accelerometer for the measurement of shock acceleration of up to 100 000 g. The structure of the accelerometer sensing chip was implemented with piezoresistive self-support beams. The piezoresistors were made in piezoresistive sensing micro-beams, which were independent of support beams, to weaken the correlation between measuring sensitivity and resonant frequency. In this way, the measuring sensitivity of the proposed novel piezoresistive accelerometer could be increased without sacrificing resonant frequency. The optimization of structural dimensions of the sensing chip was conducted through finite element method simulations. The sensing chip was fabricated employing bulk-micromachining technology with a silicon-on-insulator wafer. The fabricated accelerometer was encapsulated in stainless shell and evaluated using the Hopkinson bar system. Results demonstrated the proposed accelerometer with the measuring sensitivity of 0.54 µV/g/V and the resonant frequency of 445 kHz.