The constant development and miniaturization of MEMS sensors invariably provides new possibilities for their use in health-related and medical applications. The application of MEMS devices in posturographic systems allows faster diagnosis and significantly facilitates the work of medical staff. MEMS accelerometers constitute a vital part of such systems, particularly those intended for monitoring patients with imbalance disorders. The correct design of such sensors is crucial for gathering data about patient movement and ensuring the good overall performance of the entire system. This paper presents the design and measurements of a three-axis accelerometer dedicated for use in a device which tracks patient movement. Its main focus is the characterization of the sensor, comparing different designs and evaluating the impact of the packaging and readout circuit integration on sensor operation. Extensive testing and measurements confirm that the designed accelerometer works correctly and allows identifying the best design in terms of sensitivity/stability. Moreover, the response of the proposed sensor as a function of the applied acceleration demonstrates very good linearity only if the readout circuit is integrated in the same package as the MEMS sensor.

In this work, we analysed the difference between the measurement and simulation results of thermal drift of a custom designed capacitive MEMS accelerometer. It was manufactured in X-FAB XMB10 technology together with a dedicated readout circuit in X-FAB XP018 technology. It turned out that the temperature sensitivity of the sensor’s output is nonlinear and particularly strong in the negative Celsius temperature range. It was found that the temperature drift is mainly caused by the MEMS sensor and the influence of the readout circuit is minimal. Moreover, the measurements showed that this temperature dependence is the same regardless of applied acceleration. Simulation of the accelerometer’s model allowed us to estimate the contribution of post-manufacturing mismatch on the thermal drift; for our sensor, the mismatch-induced drift accounted for about 6% of total thermal drift. It is argued that the remaining 94% of the drift could be a result of the presence of residual stress in the structure after fabrication.

In this paper we present the main concept of an electronic device, destined to work as a part of a system devoted to monitoring human gait and movement in daily life. Operation of the device and the whole system is focused on diagnosis of the imbalance disorders, especially in elderly persons. This small electronic device is intended to be worn by the monitored person in non-restraining and comfortable manner. The data collected by the device are to be sent to accompanying data processing unit in form of e.g. a smartphone. After initial processing, the obtained data are then sent to a medical center for raising alert, further processing and storage. The paper is focused on design of a microelectromechanical system (MEMS) and an application-specific integrated circuit (ASIC) responsible for gathering, conditioning and conversion of the data into digital form best suited for quantitative analysis and transmission.

One of the most crucial step in designing of MEMS devices is modelling. It allows estimating the performance of a device without its fabrication and it provides fast optimization process. Very often it is desired to perform a coupled electromechanical simulation when a device integrates sensor and read-out circuit. A classical method uses FEM simulation. Although it is very precise, it requires building 3-D model, solving complex equations and does not provide electrical simulation of IC circuit. Therefore, there are other commercial solutions available on the market that may be coupled with CADENCE environment. In this paper, we propose to use an analytical model that can be exported to CADENCE as a black-box cell described in Verilog-A language. As an example, we take MEMS Z-axis comb-drive accelerometer whose mechanical part behave like an torsional harmonic oscillator. We include also the influence of fringing field. The model is compared with MEMS+ software in terms of electrical parameters that are inputs for electrical simulation of read-out circuit.