This paper reports the design and analysis of a type of piezoresistive pressure sensor for micro-pressure measurement with a cross beam-membrane (CBM) structure. This new silicon substrate-based sensor has the advantages of a miniature structure and high sensitivity, linearity, and accuracy. By using the finite element method to analyze the stress distribution of the new structure and subsequently deducing the relationship between structural dimensions and mechanical performances, equations used to determine the CBM structure are established. Based on the CBM model and our stress and deflections equations, sensor fabrication is then performed on the silicon wafer via a process including anisotropy chemical etching and inductively coupled plasma. The structure's merits, such as linearity, sensitivity, and repeatability, have been investigated under the pressure of 5 kPa. Our results show that the precision of these equations is ±0.19%FS, indicating that this new small-sized structure offers easy preparation, high sensitivity, and high accuracy for micro-pressure measurement.
The paper presents a piezoresistive absolute micro pressure sensor, which is of great benefits for altitude location. In this investigation, the design, fabrication, and test of the sensor are involved. By analyzing the stress distribution of sensitive elements using finite element method, a novel structure through the introduction of sensitive beams into traditional bossed diaphragm is built up. The proposed configuration presents its advantages in terms of high sensitivity and high overload resistance compared with the conventional bossed diaphragm and flat diaphragm structures. Curve fittings of surface stress and deflection based on ANSYS simulation results are performed to establish the equations about the sensor. Nonlinear optimization by MATLAB is carried out to determine the structure dimensions. The output signals in both static and dynamic environments are evaluated. Silicon bulk micromachining technology is utilized to fabricate the sensor prototype, and the fabrication process is discussed. Experimental results demonstrate the sensor features a high sensitivity of 11.098 μV/V/Pa in the operating range of 500 Pa at room temperature, and a high overload resistance of 200 times overpressure to promise its survival under atmosphere. Due to the excellent performance above, the sensor can be applied in measuring the absolute micro pressure lower than 500 Pa.
We study the focusing properties of a double-ring-shaped azimuthally polarized beam through an annular high NA objective lens. It is shown that a subwavelength focal hole (∼0.5λ) with a quite long depth of focus (∼26λ) is achieved near the focus. This kind of nondiffracting focal hole is called dark channel, which may have applications in atom optical experiments, such as with atomic lenses, atom traps, and atom switches.
This paper describes a design method for optimizing sensitivity of piezoresistive pressure sensor in high-pressure and high-temperature environment. In order to prove the method, a piezoresistive pressure sensor (HPTSS) is designed. With the purpose of increasing sensitivity and to improve the measurement range, the piezoresistive sensor adopts rectangular membrane and thick film structure. The configuration of piezoresistors is arranged according to the characteristic of the rectangular membrane. The structure and configuration of the sensor chip are analyzed theoretically and simulated by the finite element method. This design enables the sensor chip to operate in high pressure condition (such as 150 MPa) with a high sensitivity and accuracy. The silicon on insulator wafer is selected to guarantee the thermo stability of the sensor chip. In order to optimize the fabrication and improve the yield of production, an electric conduction step is devised. Series of experiments demonstrates a favorable linearity of 0.13% and a high accuracy of 0.48%. And the sensitivity of HTPSS is about six times as high as a conventional square-membrane sensor chip in the experiment. Compared with the square-membrane pressure sensor and current production, the strength of HPTTS lies in sensitivity and measurement. The performance of the HPTSS indicates that it could be an ideal candidate for high-pressure and high-temperature sensing in real application.
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