In this work, we propose a facile, low-cost, and cleanroom-free approach for fabricating flexible capacitive pressure sensors based on paintable Ag electrodes on stationery paper substrates (Ag-paper electrodes) and a random microstructured polydimethylsiloxane (PDMS) dielectric layer transferred from emery paper. COMSOL Multiphysics simulations and experimental investigations suggest that the pressure sensor with random microstructured PDMS dielectric layer performs better than the sensor with ordered micropyramidal dielectric layer. The developed Ag-paper electrode and random microstructured PDMS dielectric layer-based pressure sensors are workable in a wide pressure range (up to 630 kPa) and exhibit a high sensitivity of 0.132 kPa-1 up to 1 kPa, low hysteresis (6.6%) with loading-unloading of similar to 500 kPa pressure, high stability during a similar to 5250 cyclic test, and the ability to sense a low pressure of similar to 27 Pa. The developed sensor also successfully transduces arterial pulse wave forms when it is properly attached to the wrist. Using the proposed process, a flexible capacitive pressure sensor matrix of 4 x 4 array is also successfully developed for single- and multiple-point pressure mapping with minimal cross-talk. The proposed sensor process is simple and inexpensive to implement, and offers spatial pressure mapping for e-skin applications.

On the 4H-SiC substrate, C-face and Si-face oxide layers have been grown by thermal oxidation process and sputtering. The thermal oxidation temperature dependence of 4H-silicon carbide (SiC) is systematically investigated using capacitance-voltage (C–V) measurements. The oxidation quality and thickness vary according to the temperature and time duration of the thermal oxidation. The layers’ thicknesses are determined by atomic force microscopy (AFM), and the temperature range is between 800°C and 1110 °C. The primary reason to fabricate the Metal-Oxide-Silicon (MOS) capacitor is to know the thermal oxidation process and a working principle. In this paper, we optimize a thermal oxidation process and fabricate the MOS structure. Then we determine the various parameters such as flat band voltage (V f b ), Inversion threshold voltage (V t ), Surface depletion capacitance (C dep ), Oxide capacitance (C ox ), the total capacitance of the device (C o ), doping concentration (N d ), Depletion width (X d ), Maximum depletion width (X dt ) and Interface trap density (D it ). Finally, we analyze and discuss the MOS capacitance.

This paper reports a novel shadow mask aligner, which is capable of aligning planar with similar to 1 mu m alignment error as well as provision to compensate the wedge error by using movements of three precision linear actuators, spotted under optical microscope. The use of three points leveling also overcomes the common error of the upper assembly bending, which could occur with time after its continuous use. The reported wafer/mask holding mechanism is able to accommodate substrates of 3 '' to 6 '' diameter. The unique magnetic clamping mechanism after alignment has been successfully demonstrated. The fabricated system is useful for alignment of mask and wafer, as well as for other applications like nano-imprint and micro-contact printing lithography. In these cases, moulds/stamp is aligned with the patterned/un-patterned target substrate; to create complex 3D structures micro-assembly of independently fabricated 2D components by proper aligning and clamping.

Here, we report on the experimental and theoretical understanding of seamless junction Au mesh network flexible transparent heaters. Three Au mesh transparent conductors (TCs) are fabricated using the photolithography-etching process to compare the influence of metal surface coverage on their electrical and thermal performance. The fabricated mesh networks are quite transparent (T similar to 80%) in the 400-900 nm spectral region and exhibit small variation in sheet resistance (Delta R-max similar to 0.12, 0.05, and 0.22 Omega square(-1)) under different bending radii (minimum radii of similar to 7.5 mm). The Au mesh with large surface coverage (i.e. similar to 4.8%) exhibited the highest figure of merit (1035), and the Au mesh with small surface coverage (i.e. similar to 2.5%), which eventually tested as a heater, exhibited the highest thermal efficiency (i.e. 249 degrees C/(W/cm(2))) and temperature of 150 degrees C at the lowest input power (0.5 W cm(-2)). A 1D analytical heat transfer model is developed for quick estimation of temperature of heater samples. The thermal simulation of heaters is carried out using an ANSYS tool. The experimental, simulation and 1D analytical results are compared and validated, revealing that the simulation results are more aligned with experimental results. The flexible TCs with short response time and high thermal resistance are very useful in various flexible heating applications.

Substrate masking plays an important role in wet chemical etching process, however; coating a cost effective masking material with higher stability in the harsh chemical environment is still a challenge in MEMS technology. The durability of a masking material is determined by its capability in withstanding harsh chemicals, whether the material is a soft mask, hard mask or even a metal mask. Conventional substrate masking over wafers includes metal masks or thick photoresist (PR) masks or even multilayer masking. This paper presents an efficient procedure for substrate masking using an uncommon, less viscous photoresist. The optimization results of this photoresist have been reported in this paper. By optimization, an optimal procedure to withstand the PR in harsh chemicals was formulated. The method is highly reliable and cost effective. This procedure was implemented for different MEMS applications to prove the feasibility of substrate masking.

Excellence in the performance of MEMS-based devices such as RF switches, microfluidics, and pressure sensors are well known and by now reported. Operations of these devices are very sensitive to the environmental factors such as contamination, humidity, vibrations etc. Thus, the integration of these micro-devices with the real-life systems could be challenging without a hermetic sealing. A very common practice for these sealing is to bond a recessed cap onto a micromachined wafer using low-temperature wafer bonding mechanism known as anodic bonding or high-temperature sealing techniques such as fusion bonding for vacuum packages. Considering the limit of high-temperature bonding due to thin-film metals like nickel and gold present on the wafer and the induced bow associated with this high-temperature, this paper reveals a devising electrode designed that successfully bonded the samples at a reduced temperature well below at 250 °C. The reliability and effects of this low-temperature bonding between the silicon and Pyrex glass using destructive and non-destructive mechanisms have been investigated in this paper. The tensile strength measurements indicated a superior bonding strength of 14.12 MPa for the sample bonded at 250 °C. The induced bow height reduced from 30.3 µm (at 450 °C) to 0.3 µm (at 250 °C) meaning a significant reduction of bow up to 80.2%. Elemental composition was studied at the interface using energy dispersive X-ray spectroscopy (EDAX). To evaluate the bond quality, infra-red (IR) imaging was performed on the bonded sample pair. The interfaces were examined and analysed by scanning electron microscopy (SEM). Finally, we implemented this technique for a MEMS based pressure sensor application to prove the feasibility of low-temperature anodic bonding.

Photolithography plays a vital role in micromachining process however; coating a thin and uniform resist layer on a non-planar surface is a challenging task for micro-electro-mechanical system (MEMS). Conventional spin coating of photoresist (PR) over an un-even surface would deliver streaks all over the wafer surface. Spray coating of PR is a promising technique when compared to other candidates. This paper presents an efficient pattern transfer of microstructures between the bulk micromachined cavities over silicon and glass wafers using an uncommon photoresist mixture being spray coated. The method is simple and highly cost effective. Finally we implemented this technique for a MEMS application to prove the feasibility of spray coating for microstructure fabrication.