Design Optimization and Fabrication of a Novel Structural SOI Piezoresistive Pressure Sensor with High Accuracy.

This paper presents a novel structural piezoresistive pressure sensor with four-grooved membrane combined with rood beam to measure low pressure. In this investigation, the design, optimization, fabrication, and measurements of the sensor are involved. By analyzing the stress distribution and deflection of sensitive elements using finite element method, a novel structure featuring high concentrated stress profile (HCSP) and locally stiffened membrane (LSM) is built. Curve fittings of the mechanical stress and deflection based on FEM simulation results are performed to establish the relationship between mechanical performance and structure dimension. A combination of FEM and curve fitting method is carried out to determine the structural dimensions. The optimized sensor chip is fabricated on a SOI wafer by traditional MEMS bulk-micromachining and anodic bonding technology. When the applied pressure is 1 psi, the sensor achieves a sensitivity of 30.9 mV/V/psi, a pressure nonlinearity of 0.21% FSS and an accuracy of 0.30%, and thereby the contradiction between sensitivity and linearity is alleviated. In terms of size, accuracy and high temperature characteristic, the proposed sensor is a proper choice for measuring pressure of less than 1 psi.

Fabrication of a superhydrophobic Al2O3 surface using picosecond laser pulses.

Ultrashort pulse laser (USPL) machining/structuring is a promising technique to create a micropattern on a material surface with very low distortion to the peripheral area or high precession. Thin sheets of alumina (Al2O3) are micromachined with ultraviolet laser pulses of 6.7 ps, to create a superhydrophobic surface by single-step processing. USPL patterned micropillars and microholes have been fabricated with a range of pulses varying from 100 to 1200 pulses/unit area. The impact of the number of pulses/unit area with respect to the geometry and static contact angle measurements has been studied. The surface is free from cracks, and the melting effect is well-pronounced for the blind microhole structures. An energy dispersive X-ray spectroscopy study revealed a marginal change in the elemental composition of the laser-patterned surface. The results show that the geometry of the laser-machined pattern plays a major role in changing the wetting properties rather than the chemical changes induced on the surface. The micropillars exhibited a consistent superhydrophobic surface with a static contact angle measurement of 150° ± 3°.

Laser-induced nanoscale superhydrophobic structures on metal surfaces.

The combination of a dual-scale (nano and micro) roughness with an inherent low-surface energy coating material is an essential factor for the development of superhydrophobic surfaces. Ultrashort pulse laser (USPL) machining/structuring is a promising technique for obtaining the dual-scale roughness. Sheets of stainless steel (AISI 304 L SS) and Ti-6Al-4V alloys were laser-machined with ultraviolet laser pulses of 6.7 ps, with different numbers of pulses per irradiated area. The surface energy of the laser-machined samples was reduced via application of a layer of perfluorinated octyltrichlorosilane (FOTS). The influence of the number of pulses per irradiated area on the geometry of the nanostructure and the wetting properties of the laser-machined structures has been studied. The results show that with an increasing number of pulses per irradiated area, the nanoscale structures tend to become predominantly microscale. The top surface of the microscale structures is seen covered with nanoscale protrusions that are most pronounced in Ti-6Al-4V. The laser-machined Ti-6Al-4V surface attained superhydrophobicity, and the improvement in the contact angle was >27% when compared to that of a nontextured surface.

Chemical analysis on laser processed Ultrahydrophobic Ti-6Al-4V surface by high vacuum Process.

A technique has been developed for fabrication of ultrahydrophobic Ti-6Al-4V surface by vacuum process. This report has the data related to the article "Hybrid laser and vacuum process for rapid ultrahydrophobic Ti-6Al-4 V surface formation" on the fabrication of ultrahydrophobic Ti-6Al-4V by Vacuum process (Jagdheesh et al., 2019). The present data consist of X-ray photo electron spectroscopy spectrums recorded for the laser patterned ultrahydrophobic samples, droplet image and surface chemical composition of laser patterned Ti-6Al-4V samples before vacuum process(b. v. p.) and after vacuum process (a. v. p.) for 120 min. The presented data give a clear idea about the chemical modification evolved during the vacuum process.