Zhenyuan Sun

Microelectromechanical Systems-Based Electrochemical Seismic Sensors With Insulating Spacers Integrated Electrodes for Planetary Exploration

This paper presents a microelectromechanical system (MEMS)-based electrochemical seismic sensor for a planetary exploration. An insulating spacer and an electrode of the device are fabricated on one silicon wafer, thus decreasing the number of wafers, facilitating wafer-level alignment and enabling the fabrication of thin insulating spacers (50 μm). The proposed device achieves a sensitivity of 1978.2 V/(m/s) ( f = 1 Hz) and a noise level of 100 (nm/s)/Hz1/2 (3.2 ng/Hz1/2, f = 0.02 Hz). Side-by-side random vibration experiment shows that the prosed devices have a correlation coefficient of 0.955±0.029 (n = 7), indicating a high repeatability. Moreover, the proposed devices located in Beijing can effectively record the seismic motion signal of the Nepal earthquake (over 3000 km away), suggesting a capability of detecting remote quake events.

An electrochemical seismometer with frequency features under regulation

This paper presents a MEMS based electrochemical seismometer with controllable insulating layers, enabling the active regulation of the frequency characteristics of the sensors. More specifically, the insulating layers were made of spin-coating SU-8 photoresist, and thus the thickness can be fine tuned by regulating the spin-coating speed. Moreover, the frequency characteristics of a series of devices with diverse structure parameters were studied experimentally. It was found that the frequency characteristics can be effectively modulated by adjusting the structure parameters of the sensing unit, including the diameter of the electrode pores and the thickness of the insulating layers.

A High-Consistency Broadband MEMS-Based Electrochemical Seismometer With Integrated Planar Microelectrodes

This paper presents a broadband micro-electromechanical systems-based electrochemical seismometer with a new sensing unit composed of planar microelectrodes and perpendicular flow channels. The proposed sensing unit only needs three main microfabrication steps, leading to high consistency among devices which was quantified as 0.9978 ± 0.00050. Moreover, due to the new structure of the propose sensing unit, the raw device was featured with higher sensitivity [215.5 V/(m/s)], lower central working frequency (1 Hz), and wider working bandwidth (0.12–10.5 Hz) than previous reports. Based on the wide raw bandwidth, a broadband electrochemical seismometer was developed by the force balancing negative feedback with the final working bandwidth of 4.2 decades (0.0071–113 Hz). The linearity error and total harmonic distortion were both decreased by the feedback technology. In addition, the proposed devices demonstrated comparable self-noise level with the high-performance commercial counterpart “Trillium Compact.” Random seismic recording test was also conducted where the proposed device recorded a local earthquake with high consistency with the STS-2.5 deployed in the permanent station.

Temperature effects on characteristics of MEMS based electrochemical seismic sensors for linear motion detecting

This paper first investigates the mechanism of the temperature effects on characteristics of MEMS based electrochemical seismic sensors for linear motion detecting both by numerical simulation and experimental methods. Both the simulation and experimental results indicates that the device sensitivity increases with temperature and the tendency of the device frequency response remains the same under different temperatures, providing crucial information for further electronic compensation. The average device temperature sensitivity at different frequency points obtained by the simulation and the experiment is 1.30%/°C and 1.88%/°C (compared with the device sensitivity), respectively, indicating that the intensified electrochemical reaction caused by the increasing temperature is the primary factor (69%) for the increasing device sensitivity and the thermal effects on the electrolyte solution flow and the ion transfer are the secondary factors.

A Flexible Sensing Unit Manufacturing Method of Electrochemical Seismic Sensor

This paper presents an electrochemical seismic sensor in which paraylene was used as a substrate and insulating layer of micro-fabricated electrodes, enabling the detection of seismic signals with enhanced sensitivities in comparison to silicon-based counterparts. Based on microfabrication, paralene-based electrochemical seismic sensors were fabricated in which the thickness of the insulating spacer was 6.7 μm. Compared to silicon-based counterparts with ~100 μm insulating layers, the parylene-based devices produced higher sensitivities of 490.3 ± 6.1 V/(m/s) vs. 192.2 ± 1.9 V/(m/s) at 0.1 Hz, 4764.4 ± 18 V/(m/s) vs. 318.9 ± 6.5 V/(m/s) at 1 Hz, and 4128.1 ± 38.3 V/(m/s) vs. 254.5 ± 4.2 V/(m/s) at 10 Hz. In addition, the outputs of the parylene vs. silicon devices in response to two transit inputs were compared, producing peak responses of 2.97 V vs. 0.22 V and 2.41 V vs. 0.19 V, respectively. Furthermore, the self-noises of parylene vs. silicon-based devices were compared as follows: −82.3 ± 3.9 dB vs. −90.4 ± 9.4 dB at 0.1 Hz, −75.7 ± 7.3 dB vs. −98.2 ± 9.9 dB at 1 Hz, and −62.4 ± 7.7 dB vs. −91.1 ± 8.1 dB at 10 Hz. The developed parylene-based electrochemical seismic sensors may function as an enabling technique for further detection of seismic motions in various applications.

A Monolithic Electrochemical Micro Seismic Sensor Capable of Monitoring Three-Dimensional Vibrations

A monolithic electrochemical micro seismic sensor capable of monitoring three-axial vibrations was proposed in this paper. The proposed micro sensor mainly consisted of four sensing units interconnected within flow channels and by interpreting the voltage outputs of the sensing units, vibrations with arbitrary directions can be quantified. The proposed seismic sensors are fabricated based on MEMS technologies and characterized, which produced sensitivities along x, y, and z axes as 2473.2 ± 184.5 V/(m/s), 2261.7 ± 119.6 V/(m/s), and 3480.7 ± 417.2 V/(m/s) at 30 Hz. In addition, the vibrations in x-y, x-z, and y-z planes were applied to the developed seismic sensors, leading to comparable monitoring results after decoupling calculations with the input velocities. Furthermore, the results have shown its feasibilities for seismic data recording.

High-sensitivity electrochemical seismometers relying on parylene-based microelectrodes

This paper presents an electrochemical seismometer with parylene based microelectrodes for detecting micro seismic signals. Compared to silicon based counterpart, parylene based microelectrodes can effectively decrease the thickness of the insulating layer, which contributes to the increase in sensitivity and decrease in cost. The proposed electrochemical seismometer was designed, fabricated and characterized, producing a sensitivity of one order higher than silicon based counterpart.

A MEMS based integrated three axial electrochemical seismic sensor

This paper firstly presents an integrated three-axis electrochemical micro seismic sensor, which consists of four sensing units. The direction of the flow is opposite in different channel so that differential current can be calculated. Vertical vibration can also be detected by the addition of the output from four sensing units. Instead of huge volume in conventional three-axis sensor, the integrated device has an extremely small size same as single independent sensor because of the decoupling sensing mechanism. Micro-Electro-Mechanical System technology is used in the fabrication progress of the sensing unit. The output voltage in normalization of different axis when applying the constant vibration is 0.21 to 0.42, indicating the proposed device had great feasibility. Compared to the reference device (Trillium compact), the correlations for the same axis were calculated as 0.4473–0.8916.

Microelectromechanical system-based electrochemical seismic sensors with an anode and a cathode integrated on one chip

This paper presents a microelectromechanical system (MEMS)-based electrochemical seismic sensor with an anode and a cathode integrated on a single chip. The proposed approach decreases the number of requested wafers as the sensing unit from seven to two. In addition, no alignment and no bonding among the electrodes are needed, significantly simplifying the fabrication process. The experimental results indicate that the proposed device produced a sensitivity of 5771.7 V (m s−1)−1 at 1.4 Hz and a noise level of −163 dB (i.e. 7.1 (nm s−1)/Hz1/2) at 1 Hz. Moreover, the proposed device effectively responds to random ground motions, enabling the detection of low-frequency seismic motions caused by earthquake events.

A MEMS based electrochemical seismometer with a novel integrated sensing unit

This study proposed a new process to fabricate the sensing unit of an electrochemical seismometer using only one silicon wafer. Based on this new fabrication process, the effective area of electrodes and the fabrication efficiency were significantly improved. In this study, the SU-8 negative photoresist was utilized as both the substrate (exposed SU-8) and the sacrificial layer (unexposed SU-8) on top of which the suspended platinum electrodes were fabricated using the positive-photoresist lift-off technology. The performances of the proposed devices were characterized experimentally where compared to the commercially available counterpart CME6011, significant improvements in 3 dB working bandwidth (0.11 Hz ~21.50 Hz vs. 0.47 Hz ~18.24 Hz) and device sensitivity (1592V/(m/s) vs. 820 V/(m/s)) were located.