Mihai Gologanu

Damping effects in MEMS resonators

Damping effects are very important in MEMS-based sensors and actuators. In this paper we use analytical models and finite element (FE) computations to quantify the energy losses due to viscous fluid damping, acoustic radiation and thermo-elastic damping. To treat the case where squeeze/slide film models can not be applied, we have implemented in a commercial FE package a new incompressible flow solver based on a gauge formulation. We are thus able to solve for full flows around complex 3D geometries in the frequency domain and predict viscous damping of resonant MEMS structures. The full methodology is exemplified on the response of a MEMS silicon resonator, including acoustic driving and piezoelectric sensing.

SOI membrane-based pressure sensor in stress sensitive differential amplifier configuration

This paper introduces a pressure sensing structure configured as a stress sensitive differential amplifier (SSDA), built on a Silicon-on-Insulator (SOI) membrane. Theoretical calculation show the significant increase in sensitivity which is expected from the pressure sensors in SSDA configuration compared to the traditional Wheatstone bridge circuit. Preliminary experimental measurements, performed on individual transistors placed on the membrane, exhibit state-the-art sensitivity values (1.45mV/mbar).

Modeling thermal conductivity of graphene-based nanocomposites

We report a general setting in which the thermal conductivity of nanocomposites can be calculated. Interfacial thermal resistance is also considered and no shape assumptions are made. By this method we have found that oblate spheroidal approximation of graphene nanodots in graphene-based nanocomposites is not adequate to model thermal conductivity of these composites.

Oxygen sensor based on photo acoustic effect

This paper presents a potentially cheap oxygen sensor based on photo acoustic (PA) principle. Commercially available low cost devices are used for this implementation. The presentation is focused on aspects related to PA signal analysis, PA chamber influence on sensor response and environmental humidity impact on sensor sensitivity.