Capacitive Microelectromechanical Systems Research Articles

AUTOMATED GRAVIMETRIC SYSTEM WITH ELEMENTS OF ARTIFICIAL INTELLIGENCE TO SEARCH FOR MINERALS

The article is devoted to a topical problem – gravimetric study of the Earth for the presence of mineral deposits. To solve the problem, a system of automated gravimetric surveying with elements of artificial intelligence for the search for minerals has been developed. The proposed system of intelligent determination of minerals in gravitational exploration works uses a two-channel capacitive gravimeter as a sensitive element. The advantages of this system include: the speed of determining the key points where there is a deviation of free fall acceleration, the ability to work in hard-to-reach regions of the globe with unmanned aerial vehicles, high accuracy through the use of the last two-channel capacitive MEMS gravimeter. The advantages of MEMS (Micro Electro-Mechanical System) include high accuracy compared to analog devices, low cost of production in mass production. The small size of MEMS-gravimeters allows to expand the scope and increase the functionality of use in miniature research systems. The high accuracy of the gravimeter used in the system is achieved by reducing the main measurement errors by using two channels. The advantages also include efficiency, as it does not require the use of a large number of expensive devices and systems. The dependences of mineral on the magnitude of free fall acceleration are determined in the work and fuzzy rules of their determination are developed. According to engraving, conducted using the proposed automated gravimetric system with elements of artificial intelligence, we can with some probability talk about the presence of minerals such as copper, magnetite, coal and others. At the same time information processing time is reduced. Further clarification of the depth and size of the mineral deposit requires additional geological and geophysical research, such as the use of remote spectral and structural analysis of minerals with the involvement of satellite exploration.

A Systematic Design Optimization Approach for Multiphysics MEMS Devices Based on Combined Computer Experiments and Gaussian Process Modelling.

This paper presents a systematic and efficient design approach for the two degree-of-freedom (2-DoF) capacitive microelectromechanical systems (MEMS) accelerometer by using combined design and analysis of computer experiments (DACE) and Gaussian process (GP) modelling. Multiple output responses of the MEMS accelerometer including natural frequency, proof mass displacement, pull-in voltage, capacitance change, and Brownian noise equivalent acceleration (BNEA) are optimized simultaneously with respect to the geometric design parameters, environmental conditions, and microfabrication process constraints. The sampling design space is created using DACE based Latin hypercube sampling (LHS) technique and corresponding output responses are obtained using multiphysics coupled field electro–thermal–structural interaction based finite element method (FEM) simulations. The metamodels for the individual output responses are obtained using statistical GP analysis. The developed metamodels not only allowed to analyze the effect of individual design parameters on an output response, but to also study the interaction of the design parameters. An objective function, considering the performance requirements of the MEMS accelerometer, is defined and simultaneous multi-objective optimization of the output responses, with respect to the design parameters, is carried out by using a combined gradient descent algorithm and desirability function approach. The accuracy of the optimization prediction is validated using FEM simulations. The behavioral model of the final optimized MEMS accelerometer design is integrated with the readout electronics in the simulation environment and voltage sensitivity is obtained. The results show that the combined DACE and GP based design methodology can be an efficient technique for the design space exploration and optimization of multiphysics MEMS devices at the design phase of their development cycle.

An efficient design of dual-axis MEMS accelerometer considering microfabrication process limitations and operating environment variations

PurposeThis paper aims to present an efficient design approach for the micro electromechanical systems (MEMS) accelerometers considering design parameters affecting the long-term reliability of these inertial sensors in comparison to traditional iterative microfabrication and experimental characterization approach. Design/methodology/approachA dual-axis capacitive MEMS accelerometer design is presented considering the microfabrication process constraints of the foundry process. The performance of the MEMS accelerometer is analyzed through finite element method– based simulations considering main design parameters affecting the long-term reliability. The effect of microfabrication process induced residual stress, operating pressure variations in the range of 10 mTorr to atmospheric pressure, thermal variations in the operating temperature range of −40°C to 100°C and impulsive input acceleration at different input frequency values is presented in detail. FindingsThe effect of residual stress is negligible on performance of the MEMS accelerometer due to efficient design of mechanical suspension beams. The effect of operating temperature and pressure variations is negligible on energy loss factor. The thermal strain at high temperature causes the sensing plates to deform out of plane. The input dynamic acceleration range is 34 g at room temperature, which decreases with operating temperature variations. At low frequency input acceleration, the input acts as a quasi-static load, whereas at high frequency, it acts as a dynamic load for the MEMS accelerometer. Originality/valueIn comparison with the traditional MEMS accelerometer design approaches, the proposed design approach focuses on the analysis of critical design parameters that affect the long-term reliability of MEMS accelerometer.

A MEMS Ultra-Wideband (UWB) Power Sensor with a Fe-Co-B Core Planar Inductor and a Vibrating Diaphragm Capacitor.

The design of a microelectromechanical systems (MEMS) ultra-wideband (UWB) RMS power sensor is presented. The sensor incorporates a microfabricated Fe-Co-B core planar inductor and a microfabricated vibrating diaphragm variable capacitor on adhesively bonded glass wafers in a footprint area of 970 × 970 µm2 to operate in the 3.1–10.6 GHz UWB frequency range. When exposed to a far-field UWB electromagnetic radiation, the planar inductor acts as a loop antenna to generate a frequency-independent voltage across the MEMS capacitor. The voltage generates a coulombic attraction force between the diaphragm and backplate that deforms the diaphragm to change the capacitance. The frequency-independent capacitance change is sensed using a transimpedance amplifier to generate an output voltage. The sensor exhibits a linear capacitance change induced voltage relation and a calculated sensitivity of 4.5 aF/0.8 µA/m. The sensor can be used as a standalone UWB power sensor or as a 2D array for microwave-based biomedical diagnostic imaging applications or for non-contact material characterization. The device can easily be tailored for power sensing in other application areas such as, 5G, WiFi, and Internet-of-Things (IoT). The foreseen fabrication technique can rely on standard readily available microfabrication techniques.

Design, analysis and fabrication of the CPW resonator loaded by DGS and MEMS capacitors

In this paper, an analytical method of resonant frequency, tuning range, the effective relative dielectric constant, and characteristic impedance is proposed, which is for coplanar waveguide (CPW) resonator loaded by defected ground structure (DGS) and micro-electromechanical systems (MEMS) capacitors. The analytical solution is achieved by an employing equivalent method. The resonant frequency, tuning range, and effective relative dielectric constant are obtained by the analytical solution. For verifying the effectiveness of the proposed method, a CPW tunable bandstop filter (BSF) with DGS and MEMS capacitors is designed, simulated, and fabricated, results show good effectiveness of the proposed analysis method. By changing the height of the MEMS beam with the actuation voltage, the designed BSF can switch the center frequency among three states (i.e. 18.5 GHz, 18.2 GHz, 17.5 GHz, respectively), and fractional bandwidth is changed as well (i.e. 37.8%, 45.6%, 49.5%, respectively).

An adaptive sliding mode controller design to cope with unmatched uncertainties and disturbance in a MEMS voltage reference source

Tunable micro-electro-mechanical systems (MEMS) capacitors as the fundamental parts are embedded in MEMS AC voltage reference sources (VRS). Being concerned with the accuracy of the output voltage in the reference sources, it gets important to address uncertainties in the physical parameters of the MEMS capacitor. The uncertainties have the great inevitable potentiality of bringing about output voltage perturbation. The output deterioration is more remarkable when the uncertainties are accompanied by disturbance and noise. Manufacturers have been making great attempts to make the MEMS adjustable capacitor with desired rigorous physical characteristics. They have also tried to mitigate physical parameter veracity. However, ambiguity in the values of the parameters inescapably occurs in fabrication procedures since the micro-machining process might itself suffer from uncertainties. Employing a proportional integral (PI) adaptive sliding mode controller (ASMC), both terms of matched and unmatched uncertainties as well as the disturbance, are addressed in this work for the MEMS AC VRS so that a strict voltage is stabilized while the system is simultaneously subjected into uncertainties and exogenous disturbance. Cross-talk, some inertial forces, and electrostatic coercions may appear as matched and unmatched disturbances. Alteration in stiffness and damping coefficients might also take place as matched uncertainties due to variations in the fabrication process or even working environment. The simulation results in the paper are persuasive and the controller design has shown a satisfactory tracking performance.

A Novel Fabrication Method for a Capacitive MEMS Accelerometer Based on Glass-Silicon Composite Wafers.

In this paper, we report a novel teeter-totter type accelerometer based on glass-silicon composite wafers. Unlike the ordinary micro-electro-mechanical systems (MEMS) accelerometers, the entire structure of the accelerometer, includes the mass, the springs, and the composite wafer. The composite wafer is expected to serve as the electrical feedthrough and the fixed capacitance plate at the same time, to simplify the fabrication process, and to save on chip area. It is manufactured by filling melted borosilicate glass into an etched silicon wafer and polishing the wafer flat. A sensitivity of 51.622 mV/g in the range of ±5 g (g = 9.8 ), a zero-bias stability under 0.2 mg, and the noise floor with 11.28 µg/√Hz were obtained, which meet the needs of most acceleration detecting applications. The micromachining solution is beneficial for vertical interconnection and miniaturization of MEMS devices.

Design and Modeling of a New MEMS Capacitive Microcantilever Sensor for Gas Flow Monitoring

A new capacitive microelectromechanical system (MEMS) microcantilever gas flow sensor is introduced for application in industrial gas flow measurement pipelines. The chip encompasses microcantilevers with different lengths (50, 100, 250, and 400 μm) and the same thickness and wideness of 2 and 50 μm, respectively. Besides MEMS sensor development, we have designed a customized bypass channel based on the orifice principle for the placement of the MEMS sensor chip. Accordingly, a minibypass has been designed, which alleviates the harsh flow condition on the sensor that will be placed in the flowmeter housing. Simulations and the experimental study revealed that the sensor is capable of measuring airflows from 0 to 25 m/s with a sensitivity of 2 x 10⁻⁴ pF/m/s, and this can be expanded to other gas flow measurements with a certain bandwidth. This measurement allows us to apply this sensor for measuring moderate flows up to ~200 m/s in ~10-cm diameter pipes based on the current design for bypass. According to experimental results, the sensor output capacitance varied from 3.3445 to 3.350 pF for a range of airflow between 0 and 25 m/s. We have shown that capacitive microcantilever MEMS flow sensors could be used for flow measurements in heavy-load industrial applications.

Yield-aware multi-objective optimization of a MEMS accelerometer system using QMC-based methodologies

This paper proposes a novel yield-aware optimization methodology that can be used for mixed-domain synthesis of robust micro-electro-mechanical systems (MEMS). The robust Pareto front optimization of a MEMS accelerometer system, which includes a capacitive MEMS sensor and an analog read-out circuitry, is realized by co-optimization of the mixed-domain system where the sensor performances are evaluated using highly accurate analytical models and the circuit level simulations are carried out by an electrical simulator. Two different approaches for yield-aware optimization have been implemented in the synthesis loop. The Quasi Monte Carlo (QMC) technique has been used to embed the variation effects into the optimization loop. The results for both two- and three-dimensional yield-aware optimization are quite promising for robust MEMS accelerometer synthesis.

High-power electro-mechanical behavior of a capacitive microwave power sensor with warped cantilever beam

In this paper, high-power up to 4000 mW electro-mechanical behavior of a capacitive micro-electromechanical systems (MEMS) microwave power sensor using cantilever beam is investigated. Due to residual stress gradients, the power sensor is proposed for a warped cantilever beam connected to coplanar waveguide (CPW) structure. The proposed sensor is fabricated using the GaAs monolithic microwave integrated circuit (MMIC) process. It is demonstrated that the output response of this sensor exhibits non-linear characteristics under high power levels (more than 1000 mW). The measurement results can be classified as three regions: linear region (1–1000 mW), saturated region (1000–2500 mW), and over-saturated region (2500–4000 mW). Their corresponding sensitivities are 2.8 fF/W, 1.03 fF/W, and 0.32 fF/W at 10 GHz, respectively. The non-linear output response of the power sensor is mainly caused by impedance mismatch at X-band (8–12 GHz). Furthermore, an electro-mechanical model of power sensor based on warped cantilever beam is proposed. The results are well in agreement with the calculated ones using this model by software that employs the finite element method (FEM), which provides the potential prospect for the design of capacitive power sensor.

A high-resolution area-change-based capacitive MEMS tilt sensor

Tilt sensors have been widely used in many applications, such as instrumentation leveling, oil drilling and structural health monitoring. With the rapid development of the micro-electromechanical system (MEMS) technology, MEMS accelerometer-based high-performance tilt sensors are capable of replacing conventional tilt sensors in most of application fields. High-sensitivity MEMS resonant accelerometers (MRAs) are fully qualified for tilt sensing. However, MRA chips have to be vacuum packaged and require complex circuits; therefore, they are difficult to be miniaturized and commercialized. In this case, this paper introduces a commercial-oriented capacitive MEMS accelerometer for tilt sensing with both high-resolution and compact size. The proposed MEMS sensor utilizes simplified fabrication processes, the area-change-based capacitive displacement transducer and the capacitance-to-voltage conversion application specific integrated circuit (ASIC) for low-cost, high-sensitivity, low power consumption and miniaturization. The developed MEMS sensor has a package dimension of 14 mm × 14 mm × 3.6 mm with a single +5 V power supply and analog voltage output. Several evaluation experiments have been conducted with the results showing that the developed MEMS tilt sensor has a full measurement range of ±180°, a linear measurement range of ±30° with a nonlinearity of ±2.8%, a sensitivity of 33.6 mV/°, a noise floor of 2 × 10−4°/√Hz, a bandwidth of 100 Hz and an angle resolution of 7 × 10−4° with an integral time of 0.5 s. Compared with other commercial MEMS tilt sensors, the proposed sensor has a better resolution, a lower noise floor, a larger bandwidth, a lower power consumption and a smaller package. The simplified fabrication process and high performance suggest the developed MEMS tilt sensor is promising to be competitive in the market.

Measuring and calibrating of the parasitic mismatch in MEMS accelerometer based on harmonic distortion self-test

Capacitive MEMS (micro-electromechanical systems) accelerometers have inherent parasitic capacitors, the existence of which will increase the system bias-instability and non-linearity. The parasitic mismatch induced signal is indistinguishable to the sensed signal and cannot be canceled by traditional offset cancellation technique. In this paper, a method to realize the on-line measuring and calibrating of this parasitic effect is proposed, which is based on the digital harmonic distortion self-test. The effect of different parasitic mismatch on the system output response is analyzed in detail. As will show, in self-test mode, the parasitic mismatch will induce distinctive even-order harmonics. An on-chip digital self-test circuit is built to excite and measure this characteristic. According to the measured results, the parasitic mismatch of the front-end interface can be effectively tuned out whereby preserved calibrating unit. The test result shows, using proposed technique, the parasitic mismatch could be reduced in two orders of magnitude.

A Capacitive MEMS Inclinometer Sensor with Wide Dynamic Range and Improved Sensitivity.

This paper proposes a novel capacitive liquid metal microelectromechanical system (MEMS) inclinometer sensor and introduces its design, fabrication, and signal measurement. The sensor was constructed using three-layer substrates. A conductive liquid droplet was rolled along an annular groove of the intermediate substrate to reflect angular displacement, and capacitors were used to detect the position of the droplet. The numerical simulation work provides the working principle and structural design of the sensor, and the fabrication process of the sensor was proposed. Furthermore, the static capacitance test and the dynamic signal test were designed. The sensor had a wide measurement range from ±2.12° to ±360°, and the resolution of the sensor was 0.4°. This sensor further expands the measurement range of the previous liquid droplet MEMS inclinometer sensors.

Autonomously Tunable Filters for Interference Mitigation: Advances in Autonomously Switchable/Tunable RF/Microwave Filters for Interference Mitigation Without Operator Intervention

In wireless communication, there is a strong demand for tunable filters in scenarios that require adaptively coping with multiband interference in RF front ends. Tuning devices, ferroelectric capacitors, ferromagnetic-material-based devices, microelectromechanical systems capacitors, and piezoelectric-material-based devices are commonly used for center frequency tuning or bandwidth adjustment in tunable filter realizations. Tunable or switchable filters are essential for this desired adaptability. However, each type has thus far demonstrated its particular disadvantages. Typically, continuously tunable filters are difficult to design or require intensive use of resources to control accurately, while switchable filter banks have significant insertion loss from switching networks. Tuning capability in tunable filters often requires human intervention to control tuning frequencies or bandwidths. In this article, we introduce autonomously tunable filters to adaptively protect or mitigate receiver systems from unwanted or unreferenced signals in RF front ends using an RF-power-dependent coupling without extra control signals or closed-loop feedback of digital processing of the spectrum through analog-to-digital and digital-to-analog converters.

Design of Perforated Membrane for Low-Noise Capacitive MEMS Accelerometers

We propose a design method for a thick membrane with several thousand perforations suitable for low-noise capacitive micro-electro-mechanical systems (MEMS) accelerometers. Although we have already reported that a membrane with two-step perforations shows good noise performance, it is difficult to simulate mechanical noise using a conventional method because the large number of perforations complicates the membrane structure. In this work, we assumed that the number of perforations is infinite and that there are symmetric planes between them. This assumption greatly reduces computational complexity because the simulation model is simplified in the region around a perforation. We fabricated MEMS resonators with a two-step perforated membrane and evaluated the accuracy of the simulation results. The measured Q values of the fabricated resonators were in good agreement with the calculated results. Using this design method, we optimized the structure of a membrane with two-step perforations and fabricated capacitive MEMS accelerometers that showed excellent low-noise performance (less than 15 ng/Hz1/2) and low-power consumption (20 mW).

Linearity and RF Power Handling on Capacitive RF MEMS Switches

Linearity characteristics of capacitive tuners under large radio frequency (RF) power have become an important issue for today’s cellphone industry. The use of these devices as antenna tuners has become critically important due to the RF spectrum opening in the low-frequency range. Capacitive tuners connected directly to the antenna to change the RF voltage/current pattern and tune lower frequencies are subjected to suffer large voltage swings, especially in the isolation state or minimum capacitance. In this article, we analyze the effects of the large RF power or equivalent rms voltage to capacitive micro-electromechanical systems (MEMS) switches. The theoretical analysis combined with Coventor MEMS+ simulations will allow us to study the capacitance change and MEMS mechanical frequency response. This article evaluates two types of measurement setups to investigate the RF power effects on nominal capacitance and mechanical frequency response. Measurements up to 6 W were completed with two capacitive MEMS tuner products, confirming the modeling predictions and demonstrating the robustness of this technology under large RF power or voltage swings.

Design of a novel structure capacitive RF MEMS switch to improve performance parameters

This study reports the design and analysis of novel step structure RF micro-electromechanical system (MEMS) switch for low pull-in voltage, low insertion loss and high isolation by using uniform single meander. The central beam of the membrane is designed with 0.5 µm lower than the side beams to form a step-down structure which reduces the pull-in voltage. Stress analysis, electromechancial, switching time, quality factor and RF analysis have done to understand the behavioural characteristics of the proposed step-down switch. The analysis has been carried out for different beam and dielectric materials among them switch with gold material exhibits low pull-in voltage of 4.7 V, low insertion loss <1 dB and high isolation of −38.3 dB at 28.2 GHz for silicon nitride. The switch also shows good quality factor of 0.95 for gold material along with high capacitance ratio of 132. The upstate capacitance of 56.8 pF contributes low return loss and made the switch to transmit the signal up to 26.2 GHz and provides 7.2 pF of downstate capacitance to produce high isolation at 26.2 GHz which is efficiently used for K-band satellite applications.

Low-Density Fan-Out Heterogeneous Integration of MEMS Tunable Capacitor and RF SOI Switch

Abstract Using Low-Density Fan-Out (LDFO) packaging technology, a radio frequency (RF) microelectromechanical systems (MEMS) tunable capacitor array composed of electrostatically actuated beams on 180nm high-voltage CMOS silicon was heterogeneously integrated with a single-pole four-terminal (SP4T) RF switch on 180nm CMOS silicon-on-insulator (SOI). The primary objective of this study was to determine the manufacturability of this System-in-Package (SiP) design, which is proven at time zero through survival of the MEMS device based on acceptable MEMS performance metrics. In addition, the RF SOI switch provides high-voltage electrostatic discharge (ESD) protection for the MEMS device. Capacitive MEMS structures are particularly sensitive to unpredictable electrostatic charging scenarios, such as handling after package assembly and printed circuit board (PCB) surface mount processing. Consequently, resistance to dielectric breakdown by means of robust ESD protection is a very desirable quality. Integrating the RF switch in close proximity with the MEMS device not only enables the ability to withstand charging scenarios in excess of 1kV (human body model), it mitigates the impact of parasitics on RF performance by minimizing interconnect lengths and complexity.

(Invited) MEMS Accelerometer Fabricated by Gold Multi-Layer Metal Technology

MEMS(microelectromechanical systems) accelerometers are key devices for IoT (Internet of Things) technology. Throughout the technical progress, the resolution of detecting acceleration has been required to be the level of micro-G (1 G = 9.8 m/s2) in spite of small sensor size. In order to solve the problem, we proposed capacitive MEMS accelerometers with gold proof mass and have been developing MEMS accelerometers [1-4] using the multi-layer metal technology [5]. Figure 1 shows the relationship between the Brownian noise (BN ) and the proof mass size of MEMS accelerometers. BN is a crucial factor to determine the resolution of MEMS accelerometer [6]. In this Fig. 1, we compare our developed MEMS accelerometers with the other reported ones. These results suggest that we can obtain the low value of 22 nG/(Hz)1/2 by utilizing gold as a high density material of the proof mass, despite the same size of gold proof mass as that of silicon proof mass [7-11]. We have proved the feasibility of the MEMS accelerometer with the gold proof mass. This paper reviews the feature of our proposed MEMS accelerometer and the issue of its reliability. Figure 2 shows a schematic illustration of the proposed MEMS accelerometer. The MEMS accelerometer consists of suspensions, stoppers, a proof mass as upper electrode, and a fixed electrode. When the upper electrode is moving to the vertical direction by the input of acceleration, the capacitance is detected by the fixed electrode. The stoppers are built to prevent mechanical destruction caused by over-swinging of the upper electrode. Figure 3 shows an SEM photograph of the MEMS accelerometer. The result shows that MEMS accelerometer fabrication process is established by the multi-layer metal technology, which consists of the gold electroplating and the photo-sensitive polyimide film [5]. On the basis of the design concept and the fabrication process, we have developed the MEMS accelerometers described above. From the viewpoint of the usage of gold material for MEMS structures, we have investigated the reliability by conducting the heat cycle and the vibration cycle tests [12, 13]. These tests were carried out on MEMS accelerometers and cantilevers for evaluating the material characteristics. Figure 4 shows the results of applying the continuous vibration to the MEMS accelerometer. It is revealed that the MEMS accelerometer is immune to the vibration. In conclusion, we confirm that our proposed MEMS accelerometer can make a contribution to a new technical development. Reference [1] T. Konishi et al., Jpn. J. Appl. Phys., 52, p. 06GL04, (2013). [2] D. Yamane et al., Appl. Phys. Lett., 104, p. 074102, (2014). [3] D. Yamane et al., APCOT 2016, pp299, (2016). [4] D. Yamane et al., Sensors and Materials, (2019). [5] K. Machida et al., IEEE Trans. On ED, 48, 2273, (2001). [6] B. E. Boser and R. T. Howe, IEEE JSC, 31, p. 366, (1996). [7] J. Chae et al., JMEMS, vol.13, pp.628-635, (2004). [8] H. Qu et al., IEEE Sensors Journal, vol.8, pp.1511(2008). [9] R. G. Walmsley et al., in Proc. IEEE SENSORS2009, (2009). [10] R. A. Dias et al., Sensors and Actuators A: pp. 47 (2011). [11] X. Zou et al., in Proc. Transducers 2015, (2015). [12] T. Konishi et al., MNC 2017, (2017). [13] D. Yamane et al., Transducers 2017,2187, (2017). Figure 1

A Review of the Capacitive MEMS for Seismology.

MEMS (Micro Electro-Mechanical Systems) sensors enable a vast range of applications: among others, the use of MEMS accelerometers for seismology related applications has been emerging considerably in the last decade. In this paper, we provide a comprehensive review of the capacitive MEMS accelerometers: from the physical functioning principles, to the details of the technical precautions, and to the manufacturing procedures. We introduce the applications within seismology and earth sciences related disciplines, namely: earthquake observation and seismological studies, seismic surveying and imaging, structural health monitoring of buildings. Moreover, we describe how the use of the miniaturized technologies is revolutionizing these fields and we present some cutting edge applications that, in the very last years, are taking advantage from the use of MEMS sensors, such as rotational seismology and gravity measurements. In a ten-year outlook, the capability of MEMS sensors will certainly improve through the optimization of existing technologies, the development of new materials, and the implementation of innovative production processes. In particular, the next generation of MEMS seismometers could be capable of reaching a noise floor under the lower seismic noise (few tenths of ng/) and expanding the bandwidth towards lower frequencies (∼0.01 Hz).