A microelectromechanical system (MEMS) capacitive accelerometer-based microphone with enhanced sensitivity for fully implantable hearing aid: a novel analytical approach.

The present work proposes a novel, compact, intuitively simple and efficient structure to improve the sensitivity of a microelectromechanical system (MEMS) capacitive accelerometer using an arrangement of microlever as a displacement amplifier. The accelerometer is proposed to serve as a microphone in the fully implantable cochlear prosthetic system which can be surgically implanted at the middle ear bone structure. Therefore, the design parameters such as size, weight and resonant frequency require deliberation. The paper presents a novel analytical model considering the impact of the mechanical amplification along with the width of the microlever and the capacitive fringe effects on the performance of the sensor. The design is simulated and verified using COMSOL MULTIPHYSICS 4.2. The accelerometer is designed within a sensing area of 1 mm2 and accomplishes a nominal capacitance of 4.85 pF and an excellent sensitivity of 5.91 fF/g.

Sensitivity enhancement of a folded beam MEMS capacitive accelerometer-based microphone for fully implantable hearing application.

The present work attempts to enhance the sensitivity of a folded beam microelectromechanical systems (MEMS) capacitive accelerometer by optimising the device geometry. The accelerometer is intended to serve as a microphone in the fully implantable hearing application which can be surgically implanted in the middle ear bone structure. For the efficient design of the accelerometer as a fully implantable biomedical device, the design parameters such as size, weight and resonant frequency have been considered. The geometrical parameters are varied to obtain the optimum sensitivity considering the design constraints and the stability of the structure. The optimised design is simulated and verified using COMSOL MULTIPHYSICS 4.2. The stability of the device is ensured using eigenfrequency analysis. Optimised results of the device geometry are presented and discussed. The accelerometer has a sensing area of 1 mm2 and attains a nominal capacitance of 5.3 pF and an optimum sensitivity of 6.89 fF.

Vibrational spectra, HOMO, LUMO, MESP surfaces and reactivity descriptors of amylamine and its isomers: A DFT study.

Amylamine constitutes an important class of organic compounds which exists in a variety of ammonia derivatives. In present study, a comparative analysis of amylamine and its two potential isomers, iso-amylamine and tert-amylamine, has been performed using density functional theory with B3LYP method and 6-311G(d,p) as the basis set. The equilibrium structures of amylamine as well as its iso and tert forms have been obtained. The vibrational spectroscopic analysis has been carried out for the three molecules and complete assignments to all possible modes have been offered. The HOMO, LUMO and MESP surfaces are analyzed to discuss the chemical reactivity patterns in the molecules. A number of reactivity parameters have been calculated to further explain their chemical reactivity. The thermodynamic and nonlinear optical parameters are also calculated and discussed.