This paper presents a novel capacitive microelectromechanical systems (MEMS) accelerometer with slanted supporting beams and all-silicon sandwich structure. Its sensing mechanism is quite similar to an ordinary sandwich-type MEMS accelerometer, except that its proof mass is suspended by a beam parallel to the {111} plane of a (100) silicon wafer. In this way, each sensing element can detect accelerations in two orthogonal directions. Four of these sensing elements could work together and constitute a 3-axis micro-accelerometer by using a simple planar assembly process. This design avoids the traditional 3-axis accelerometer’ disadvantage of possible placement inaccuracy when assembling on three different planes and largely reduces the package volume. The slanted-beam accelerometer’s performance was modeled and analyzed by using both analytical calculations and finite element method (FEM) simulations. A prototype of one sensing element was fabricated and tested. Measured results show that this accelerometer has a good bias stability 76.8 ppm (1σ, tested immediately after power on), two directional sensitivities (sensitivity angle α = 45.4°) and low nonlinearity (<0.5%) over a sensing range up to ±50 g, which demonstrates a great opportunity for future high-precision three-axis inertial measurement.

The V-shaped electrothermal actuator has gained significant popularity as it was demonstrated to be a compact, stable and high rectilinear displacement device. However, existing electrothermal actuators usually require the driven voltage as high as several tens of volts to realize large displacements, imposing restrictions on the actuator’s integration in miniature mobile mechatronic systems. The paper presents a V-shaped metal-silicon actuator with low voltage, low power consumption and large displacement. The electro-thermal conversion and heat conduction mechanism of the actuator are improved by optimizing the architecture design of the actuator. An innovative method utilizing the double-sided inductively coupled plasma etching technique is developed for the fabrication. The motion of the actuator is characterized with a microscope-based dynamic test system. Finite element analysis is conducted to verify the device design and experimental results. The transient dynamic behaviour of the actuator is modelled for future control strategy. A rectilinear displacement as high as $80.7~\mu \text{m}$ is achieved at a voltage of 4.0 V and power of 1.12 W. The displacement per unit length to voltage ratio of the metal-silicon actuator is the largest among existing silicon actuators. The displacement per unit length to power of the actuator is also comparative to the highest value of existing actuators, demonstrating that the metal-silicon actuator can achieve large displacement with low voltage and power consumption. The proposed actuator has great potential for the applications in the miniature mechatronic systems such as cell phone, camera, safety and arming device. [2021-0048]

Microstructure-based function components are widely used in precision engineering. Surface profile measurement is an essential tool to verify the manufacturing quality of microstructures and to enhance the working performance of the device employing microstructures as function components. However, highly accurate surface profile measurements are difficult to perform for microstructures owing to their complex surface topographies. In this paper, a measurement system is proposed for the surface profile measurement of microstructures. The main components of the measurement system are a precision displacement stage to move the workpiece, a homemade probing system with a diamond microstylus to sense the surface profile variation of the microstructures on the workpiece, and a vibration isolation table to reduce the disturbance of the measurement environment. In addition, the stability of the measurement was experimentally investigated. Microstructures with shape of equilateral right triangle were employed as the measurement specimen, and the surface profile of triangular microstructures was measured by employing two methods to correct errors caused by the specimen inclination and the radius of the stylus tip. The shape, depth, and period of the measured microstructures were also detected based on the results of the surface profile measurement. Experimental results demonstrate the feasibility of the proposed surface profile measurement for microstructures with complex surface topographies.

Mineralization ages of many mineral deposit types (such as orogenic Au, stratabound Cu, and Mississippi Valley-type Pb-Zn deposits) are still difficult to date by the traditional isotopic chronometry because of the lack of suitable minerals. We have made efforts to establish a widely suitable dating technique to determine ore formation ages using a high-precision ⁴⁰Ar/³⁹Ar method on ubiquitously present fluid inclusions in quartz, sphalerite, and other nonpotassium minerals from hydrothermal deposits. The Xitian W-Sn polymetallic deposit in central South China contains several minerals suitable for isotopic dating for interchronometer comparison. ⁴⁰Ar/³⁹Ar laser step heating of 16 micas from ore veins, greisen, and metallogenic granites yields flat age spectra and thus well-defined ore formation ages ranging from 152.4 ± 1.5 (2σ) to 148.1 ± 1.4 Ma with an average of 150.2 ± 0.6 Ma. ⁴⁰Ar/³⁹Ar progressive crushing of nine quartz samples produces well-defined isochron lines for their primary fluid inclusions corresponding to isochron ages of 153.7–149.9 Ma with an average of 151.6 ± 0.6 Ma. Cassiterites from three hand specimens have weighted mean ²⁰⁶Pb/²³⁸U ages of 151.5 ± 1.7 (2σ), 149.7 ± 2.1, and 151.7 ± 2.1 Ma. All these new geochronological dates and previous molybdenite Re-Os ages yield well-constrained mineralization ages of 153–148 Ma for the Xitian W-Sn polymetallic deposit, which also confirms conclusively that the quartz ⁴⁰Ar/³⁹Ar progressive crushing technique is a feasible, valid dating technique. Furthermore, significant age information on the secondary fluid inclusions is potentially obtained simultaneously by this technique. We expect that this novel dating technique will be widely applied to determine the geologic fluids trapped in minerals during hydrothermal mineralization, hydrocarbon accumulation, metamorphism, tectonic activities, and other geologic processes.

Materials with high electromagnetic interference (EMI) shielding performances, excellent conductivity and flexibility, along with low density, have a great potential to be applied in next generation of flexible electronic devices. In the current study, one of such materials, reduced graphene oxide woven fabrics (rGWF)/poly(dimethyl siloxane) (PDMS) composites are fabricated through a facile template-directed reduction method followed by dip coating. The fabricated composite possesses a highly ordered and hierarchical porous structure, containing 3D interconnected graphene networks. The unique porous structure containing high-quality graphene architecture makes the composite exceptional EMI shielding properties. The composite containing four layers of rGWF delivers a remarkable total shielding effectiveness (SE_T) of 46 dB and a specific SE_T of 295 dBcm³/g. Apart from this property, the composite also exhibits excellent durability and is capable of retaining over 94% and 98% of the original SE_T after 100 stretching-releasing and bending-releasing cycles, respectively. These excellent properties in EMI shielding performance, durability, and reliability give rGWF/PDMS composite a great potential to be used as emerging flexible EMI shielding materials.