Liang-Cheng Tu

• PhD
• Professor (Full) at Sun Yat-sen University

Because classical Maxwellian electromagnetism has been one of the cornerstones of physics during the past century, experimental tests of its foundations are always of considerable interest. Within that context, one of the most important efforts of this type has historically been the search for a rest mass of the photon. The effects of a nonzero pho...

We present a new value of the Newtonian gravitational constant G by using the time-of-swing method. Several improvements greatly reduce the uncertainties: (1) measuring the anelasticity of the fiber directly; (2) using spherical source masses minimizes the effects of density inhomogeneity and eccentricities; (3) using a quartz block pendulum simpli...

A rotating torsion balance method is used to detect the product of the photon mass squared and the ambient cosmic vector potential A(e). The signal is modulated by rotating the torsion balance to ensure the effectiveness of detection for all possible orientations of the vector potential. The influences of sidereal disturbances of environment are al...

A null experimental test of the Newtonian inverse-square law at submillimeter range using a torsion pendulum was presented. Under the dual modulations of both the expected signal and the gravitational torque for calibration, our data concluded with 95% confidence that no new forces were observed and any gravitational-strength Yukawa forces (|alpha|...

Accurate thrust assessment is crucial for characterizing the performance of micro-thrusters. This paper presents a comprehensive evaluation of the thrust generated by a needle-type Indium Field Emission Electric Propulsion (In-FEEP) micro-thruster using three methods based on a pendulum: direct thrust measurement, indirect plume momentum transfer,...

TianQin is a future space-based gravitational wave observatory targeting the frequency window of $10^{-4}$ Hz $\sim 1$ Hz. A large variety of gravitational wave sources are expected in this frequency band, including the merger of massive black hole binaries, the inspiral of extreme/intermediate mass ratio systems, stellar-mass black hole binaries,...

The TianQin mission, as a space-based gravitational wave detection, aims to establish a gravitational wave observation window in the mHz frequency band. The temperature control for the core payload in this context demands extreme precision, needing to be better than 5 μK/Hz1/2. Compared to resistive and optical temperature sensors, resonant MEMS te...

The rotating accelerometer gravity gradiometer (RAGG) is a gravity gradient measuring instrument designed for moving base, and as such, the primary technical challenge in RAGG development lies in compensating for motion error. Nevertheless, the existing open researches are limited in number and exhibit several limitations: a lack of systematic desi...

A phasemeter as a readout system for the inter-satellite laser interferometer in a space-borne gravitational wave detector requires not only high accuracy but also insensitivity to amplitude fluctuations and a large fast-acquiring range. The traditional sinusoidal characteristic phase detector (SPD) phasemeter has the advantages of a simple structu...

The rotating accelerometer gravity gradiometer (RAGG) is regarded as a significant tool in geophysics applications such as resource exploration and gravity-assisted navigation research. Here we develop a prototype of the horizontal tensor RAGG and build a dedicated calibration platform for evaluating its performance. The error of calibration is the...

The gate-type carbon nanotubes cathodes exhibit advantages in long-term stable emission owing to the uniformity of electrical field on the carbon nanotubes, but the gate inevitably reduces the transmittance of electron beam, posing challenges for system stabilities. In this work, we introduce electron beam focusing technique using the self-charging...

Accelerometers are required to discern minute gravity-related variations when simultaneously measuring the large disturbing acceleration of the moving platforms in airborne or shipborne gravity gradient measurement. Closed-loop accelerometers with an electromagnetic servo actuator are commonly used to realize such a large dynamic range. However, th...

The high precision turntable plays a crucial role in the measurement of inertial sensors, aerospace applications and other fields, and thus it is imperative to evaluate and measure its angular acceleration error accurately, particularly in a rotating accelerometer gravity gradiometer (RAGG). To address the issues of delay and noise amplification ca...

The detection of gravitational waves in space requires micro-thrusters that can respond quickly to compensate for non-conservative forces on the satellite with low thrust noise. Flow measurement plays a crucial role in cold gas microthrusters, directly determining the control accuracy of thrust adjustment and the upper limit of thrust noise. It is...

The presence of strong ambient vibrations could have a negative impact on applications such as high precision inertial navigation and tilt measurement due to the vibration rectification error (VRE) of the accelerometer. In this paper, we investigate the origins of the VRE using a self-developed MEMS accelerometer equipped with an area-variation-bas...

Surface morphology of emitting tip has a significant effect on performance of Liquid-Metal Ion Sources. In this paper, fabrication technics of dynamic micro-electrochemical etching was employed to realize microgrooves processing of emitting tip surfaces at different depths by regulating roughening time and voltage frequency. Through field emission...

The metrological characteristics of source masses are essential in the determination of the Newtonian gravitational constant G. This paper presents an air-bearing method to check the density uniformity of spherical source masses by measuring the mass center offset from the geometric center. With detailed error analysis, we find that the eccentricit...

High precision accelerometers play a vital role in the measurement of the Earth’s gravitational field. They can be used in the rotating-accelerometer-based gravity gradient instrument (GGI) to detect the change of the gravity gradient. For that application, the high precision accelerometers should have a noise floor of below 1 $\text{n}{g}/ (Hz)^{...

High-precision and wide-band microthrust testing and evaluation on the ground is key to achieving precision, drag-free control, which is extremely demanding for spaceborne gravitational-wave detection missions. However, unlike a stable space environment, complex ground vibrations inevitably affect the evaluation of microthrust. To reduce the interf...

Rotating Accelerometer Gravity Gradientmeter (RAGG) is the only gravity gradient measuring device in the world to achieve commercial applications. When the parameter consistency among multiple accelerometers of the RAGG is not sufficient, its combined output cannot effectively suppress common-mode noise in the environment. A method for suppressing...

High-precision MEMS accelerometers with nano-g resolution are emergent instruments for geophysical applications and proved their competence in terms of functionality. The electromagnetic actuator, which serves as an auxiliary component in nano-g MEMS accelerometers for improving the dynamic response, faces the challenges of process incompatibility,...

The measurements of wafers’ surface profile are crucial for safeguarding the fabrication quality of integrated circuits and MEMS devices. The current techniques measure the profile mainly by moving a capacitive or optical spacing sensing probe along multiple lines, which is high-cost and inefficient. This paper presents the calculation, simulation...

Electrospray technology is widely used in many technological areas. The beam current of electrospray is an important parameter since it directly associates with the electrohydrodynamic behavior of the cone jet and can be precisely measured. Although how the beam current changes with other variables has been theoretically and experimentally research...

A MEMS (Micro‐Electro‐Mechanical) based 3‐C borehole gravimeter has being developed in China for mineral and hydrocarbon exploration. The 3‐C borehole gravimeter is composed of a three‐axis gravity sensor chip based on deep silicon etching technique, high precision capacitive displacement sensing and weak signal detection circuitry. The gravity sen...

Precision measurements of local gravitational acceleration variations are of great importance in geophysical surveys. With advantages such as cost-effectiveness and portability, Micro-Electro-Mechanical system (MEMS)-based gravimeters have shown the potential for long-term gravity measurements. In this paper, aiming to further improve the stability...

This paper introduces a nano-g level optical accelerometer based on a differential Fabry–Pérot interferometer(DFPI) for low-frequency (less than 1 Hz) noise suppression. The accelerometer has its proof-mass supported by two metal spring beams and has a natural frequency of 40 Hz. The DFPI structure is composed of two fiber end-faces and two reflect...

Area-changed capacitive displacement transducers (CDTs) are widely used in the high-precision displacement measurement due to their high accuracy and large dynamic range. The preamplifier circuit is used to convert the capacitance variation signal into voltage, which requires low noise and is significant for the high-sensitivity area-changed CDTs....

Capacitive transducers are the core of electrostatic space accelerometers and have been applied in several space science missions. However, the noise of the front-end circuit in a capacitive transducer is a major limitation to capacitance resolution. The current theoretical models cannot accurately and comprehensively describe the performance of th...

MEMS sensors have the advantages of small volume, lightweight, and low cost, therefore, have been widely used in the fields of consumer electronics, industry, health, defence, and aerospace. With their ever-improving performance, MEMS sensors have also started to be used in resource exploration and geophysical applications. However, the requirement...

The TianQin Project is aiming at gravitational wave (GW) detection in space. TianQin GW observatory comprises three satellites orbiting on $1 \times 10^5$ km Earth orbits to form an equilateral-triangle constellation. In order to minimize the variations of arm-length and breathing angle, the satellites must be launched and adjusted precisely into a...

This paper reports a miniaturized resonant Lorentz-force magnetometer that exploits blue-sideband actuation to attain a better sensitivity and resolution. The resonant magnetometer consists of a double-ended tuning fork (DETF) resonator with cavity slots to optimize thermoelastic dissipation, as well as a Lorentz-force generator structure to transd...

As an application of electrospray, electrospray thrusters are preferred to work in a steady electrohydrodynamic mode to output high-precision and adjustable thrust through controlling voltages and flow rates. However, voltages and flow rates can only be modified in a small range to avoid mode transiting, thereby limiting the thrust range. To increa...

Numerous revolutionary space missions have been initiated and planned for the following decades, including plans for novel spacecraft, exploration of the deep universe, and long duration manned space trips. Compared with space missions conducted over the past 50 years, current missions have features of spacecraft miniaturization, a faster task cycl...

This paper introduces a fiber-optic microelectromechanical system (MEMS) seismic-grade accelerometer that is fabricated by bulk silicon processing using photoresist/silicon dioxide composite masking technology. The proposed sensor is a silicon flexure accelerometer whose displacement transduction system employs a light intensity detection method ba...

In a rotating accelerometer gravity gradiometer (RAGG), rotary table wobble refers to the shift in the direction of the spin axis during operation. This motion causes errors in the output of the RAGG, but the mechanism is not clear. The purpose of this paper is to analyze the relationship between rotary table wobble and RAGG errors and to propose a...

Magnetic field affects the sensing performance of rotating accelerometer gravity gradient instrument (RAGGI) used for airborne mineral exploration and gravity aided navigation. This paper studies the error introduction mechanism of the RAGGI measurement platform caused by the environmental magnetic field. It is clarified that the inseparable functi...

Plain Language Summary The ocean currents are strongly steered by the seafloor topography. Therefore, the seafloor topography should be represented at fine resolution to study how the warm water melts the ice shelf from below. However, the seafloor beneath the largest ice shelf in East Antarctica remains poorly known, because the thick floating ice...

Limited by manufacturing technology, in moving-base gravity gradiometry, accelerometer mounting errors and mismatch cause a rotating accelerometer gravity gradiometer (RAGG) to be susceptible to its own motion. In this study, we comprehensively consider accelerometer mounting errors, accelerometer linear scale factors imbalances, accelerometer seco...

Simultaneously and independently measuring two-dimensional (2D) displacement, one-dimensional (1D) for out-of-plane measurement and 1D for in-plane measurement, is important for practical applications. Although extrinsic fiber Fabry-Perot interferometers (EFPIs) have been reported for highly precise out-of-plane displacement measurements for many y...

Magnetometers are ubiquitous in applications covering many aspects of modern life, such as navigation, smart devices, biomedical systems, geological surveying and aerospace. This work reports a resonant Lorentz-force magnetometer featuring structural topology, in which cavity slots are incorporated in the device structure to improve the thermoelast...

TianQin-1 is a mission in the TianQin project, which uses a single satellite to demonstrate the maturity of the key technology for the space-based gravitational wave detection. The spaceborne laser in the TianQin-1 mission consists of a self-developed DBR one and a commercial RIO one. The DBR laser is also developed as a pumping source for the main...

In this paper, the air buoyancy effect on Micro-Electro-Mechanical System (MEMS)-based gravity sensors for high-resolution gravity measurements is investigated. The MEMS gravimeter is operated in an atmospheric environment without any vacuum chamber; thus significantly simplifying the design, implementation and maintenance, and reducing the cost of...

An in-plane displacement sensor based on an asymmetric extrinsic fiber Fabry–Perot interferometer (EFPI) is proposed and demonstrated. The asymmetric EFPI composed of a step-shaped external reflector and a cleaved fiber end face can be equivalent to two parallel FPIs with slightly different cavity lengths. By calculating the peak intensity differen...

The reduction of temperature effect is vitally important for high precision sensors. This paper introduces the theoretical analysis and experimental verification of an in-situ compensation method on the temperature coefficient of the scale factor for a single-axis electromagnetic force-balance feedback MEMS accelerometer. A micro thermistor, fabric...

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Ultra-high sensitivity accelerometers are widely used in the space exploration and measurement of the earth's gravitational field. It's of great significance to evaluate and compensate the influence of temperature on them for improving the accuracy of the accelerometers. Analysis of the error terms are revisited in detail for their mechanism of act...

In this paper, a new approach for enhancing the temperature sensitivity of a resonant MEMS thermometer, based on parametric modulation, is proposed. By periodically modulating the effective stiffness of a standard clamped-clamped beam (C-C beam), which is used as a proof-of-concept resonant MEMS thermometer, it is possible to create a virtual energ...

The assumption of implementing a Bender-type mission with two pairs of inline satellites by two institutions, one in the inclined satellite formation (ISF) and the other in the polar satellite formation (PSF), has been proven as an optimal selection for the next-generation gravimetric mission (NGGM). The prerequisite of this assumption is to ensure...

Nano-g accelerometers are widely used in the space exploration and measurement of the earth’s gravitational field. It is essential to precisely evaluate error effects at high orders such as cross-coupling for applications in a dynamic environment. Nevertheless, it remains challenging to meet the precision requirements using conventional calibration...

Improving the precision of current tests of the equivalence principle with a rotating torsion pendulum requires a more complete analysis of systematic effects. Here, we discuss in detail one of the important systematic effects, the influence from the tilt error motion of the rotation axis of a rotary stage, namely, wandering of the instantaneous ro...

This paper describes a hybrid mass sensing system comprising a QCM (quartz crystal microbalance) mass sensor operating under atmospheric pressure and a 3-DOF mode localized coupled resonator operating in vacuum. Nanoparticles as consecutive mass perturbations are added onto the QCM, the output signals with respect to the amount of mass change are t...

Compared with airborne gravimetry, a technique frequently used to infer the seafloor topography at places inaccessible to ship soundings due to the presence of ice shelf or ice mélange, airborne gravity gradiometry inherently could achieve higher spatial resolution, thus it is promising for improved inference of seafloor topography. However, its es...

Seafloor topography shapes the pathways of ocean currents transporting ocean heat and, thus, is a fundamental boundary condition for modeling ocean‐ice interactions. However, few ship bathymetric data are available on the inner continental shelf of northeast Greenland due to the year‐round presence of sea ice. We infer seafloor topography of this r...

The TianQin-1 satellite (TQ-1), which is the first technology demonstration satellite for the TianQin project, was launched on 20 December 2019. The first round of experiment had been carried out from 21 December 2019 until 1 April 2020. The residual acceleration of the satellite is found to be about $1\times10^{-10}~\um/\us^{2}/\uHz^{1/2}$ at $0.1...

The large-scale fabrication of high performance on-chip micro-supercapacitors (MSCs) is the foot-stone for the development of next generation miniaturized electronic devices. In practical applica-tions, however, MSCs may suffer from a low areal energy density as well as complicated fabrication strategy that is incompatible with semiconductor proces...

TianQin is a planned space-based gravitational wave (GW) observatory consisting of three earth orbiting satellites with an orbital radius of about $10^5~{\rm km}$. The satellites will form a equilateral triangle constellation the plane of which is nearly perpendicular to the ecliptic plane. TianQin aims to detect GWs between $10^{-4}~{\rm Hz}$ and...

The TianQin-1 satellite (TQ-1), which is the first technology demonstration satellite for the TianQin project, was launched on 20 December 2019. The first round of experiment had been carried out from 21 December 2019 until 1 April 2020. The residual acceleration of the satellite is found to be about $1\times10^{-10}~{\rm m}/{\rm s}^{2}/{\rm Hz}^{1...

TianQin is a planned space-based gravitational wave (GW) observatory consisting of three Earth-orbiting satellites with an orbital radius of about $10^5 \, {\rm km}$. The satellites will form an equilateral triangle constellation the plane of which is nearly perpendicular to the ecliptic plane. TianQin aims to detect GWs between $10^{-4} \, {\rm Hz...

High-precision microelectromechanical inertial sensors based on spring-mass structures are of great interests for a wide range of applications, including inertial navigation, disaster warning and resource exploration. Lowering the resonant frequency is essential to further improve the sensitivity of the sensors. However, conventional approaches are...

The Newtonian gravitational constant G, which is one of the most important fundamental physical constants in nature, plays a significant role in the fields of the theoretical physics, geophysics, astrophysics, and astronomy. Although G was the first physical constant to be introduced in the history of science, it is considered to be one of the most...

Mounting requirements of a rotating accelerometer gravity gradiometer (RAGG) beyond the art of manufacture, the RAGG is susceptible to the motion of itself. Motion error is a main source of error in airborne gravity gradiometry data. This study presented a post error compensation method, which consists of post motion error compensation and post sel...

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...

Temperature sensors are one of the most important types of sensors, and are employed in many applications, including consumer electronics, automobiles and environmental monitoring. Due to the need to simultaneously measure temperature and other physical quantities, it is often desirable to integrate temperature sensors with other physical sensors,...

Area-changed capacitive displacement transducers have been widely applied in micro-electro-mechanical-system (MEMS) sensors such as sandwich-type MEMS accelerometers to detect in-plane displacement with a high sensitivity. The cross-axis disturbance could result in out-of-plane displacement of the proof mass, which brings a gap variation of sensing...

Diamagnetism as a fundamental physical phenomenon is commonly existed in many materials, such as water and even human body. Since the Nobel Prize laureate Prof. Geim successfully demonstrated the flying frog in 1997, diamagnetic levitation has attracted significant research interests due to the advantages of simple structure, stable and passive lev...

Electromagnetic wave absorbers are essential devices in imaging, wireless communication and energy harvesting systems. In this paper, we propose and experimentally demonstrate a flexible and ultra-broadband terahertz (THz) wave absorber based on graphene-vertically aligned carbon nanotube (G-VACNT) hybrids. The THz absorber consists of Cu/PDMS/grap...

Capacitive MEMS accelerometers with area-variable periodic-electrode displacement transducers found wide applications in disaster monitoring, resource exploration and inertial navigation. The bonding-induced warpage, due to the difference in the coefficients of thermal expansion of the bonded slices, has a negative influence on the precise control...

Capacitive transducers are widely used in fundamental physics experiments, seismology, Earth or planetary observations, and space scientific and technical applications because of their high precision, simple structure, and compatibility with various measurements. However, in real applications, there is a trade-off between their resolution and dynam...

We improve the test of the gravitational inverse-square law at the submillimeter range by suppressing the vibration of the electrostatic shielding membrane to reduce the disturbance coupled from the residual surface potential. The result shows that, at a 95% confidence level, the gravitational inverse-square law holds (|α|≤1) down to a length scale...