A trapezoidal cantilever density sensor is developed based on micro-electro-mechanical systems(MEMS) technology.The sensor measures fluid density through the relationship between the density and the resonant frequency of the cantilever immersed in the fluid.To improve the sensitivity of the sensor,the modal and harmonic response analyses of trapezoidal and rectangular cantilevers are simulated by ANSYS software.The higher the resonant frequency of the cantilever immersed in the fluid,the higher the sensitivity of the sensor;the higher the resonant strain value,the easier the detection of the output signal of the sensor.Based on the results of simulation,the trapezoidal cantilever is selected to measure the densities of dimethyl silicone and toluene at the temperature ranges of 30 to 55 ℃ and 26 to 34 ℃,respectively.Experimental results show that the trapezoidal cantilever density sensor has a good performance.
＜正＞Demands for miniaturized devices integrated with microelectronics lead to great interests in the design and...
Wei REN Electronic Materials Research Laboratory,Key Laboratory of the Ministry of Education & International Center for Dielectric Research,Xi''an Jiaotong University,Xi''an 710049,China
Lead-free ferroelectric K_(0.5)Na_(0.5)NbO_(3)(KNN)films with different thicknesses were prepared by polyvinlypyrrolidone(PVP)-modified chemical solution deposition(CSD)method.Their residual stresses were studied with two methods of X-ray diffraction(XRD)and nanoindentation fracture.It was found that the tensile stress occurs in KNN films with small thickness of 1.3μm after all kinds of stresses were neutralized,which is mainly originated from the interaction across grain boundaries.With increasing the thickness to 2.5μm and above it,the residual stress changed from tensile stresses to compressive stresses,and the compressive stress decreased with the thickness increased.These results could explain why a thicker KNN film can show improved electrical properties and the larger the thickness,the better the ferroelectric and piezoelectric properties.
