Today's medical implants communicate with each other over radio, typically using standards such as MICS. However, in order to reduce power consumption and improve datarates, we need to explore better standards. Ultra wide band radios (UWB) are known to be low power. While studies on UWB radios for on-body implants exists, no study exists which explains the effect of UWB for in-body medical implants. This paper shows that Ultra wideband (UWB) can be a feasible solution for in-body medical implants in certain cases. We present a model to compute path loss inside human body tissues, for frequencies in the UWB standard, a study that has not been done so far. Furthermore, we extend this model to include reflection losses. We will show from our study that UWB is an excellent option for short-distance inter-implant communication and combined in-and on-body communications.
In order to improve the photovoltaic (PV) production, the researchers are interested in developing new methods to reach the Maximum Power Point (MPP) produced by the photovoltaic field to be injected into the utility grid. This article describes a new method called the Optimized Steepest Gradient Method (OSGM), it is based on the first (gradient) and second order (hessian) derivatives of the power function in order to find the best variation of the voltage (Vpv) with the calculation of the optimal step allowing the convergence to the tension value (Vref) which ensures the MPP. The mathematical model has been developed and implemented under Matlab/Simulink environment. To analyze Maximum Power Point Tracking (MPPT) algorithm performances, time response, oscillation, overshoot and stability are taken into account. The OSGM is implemented and compared to three others algorithms (one of these algorithm is the ANFIS proposed in previous work). Performances obtained by the proposed algorithm offer faster response, less oscillations around MPP and a low energy loss. In addition, numerical computation of the gradient and the hessian of the power function allow bypassing modeling inaccuracies.
The objective of this paper is to present a new technology that integrates a Micro Electro-Mechanical Systems (MEMS) accelerometer and an Application-Specific Integrated Circuit (ASIC) chip encapsulated in a hermetic silicon box that could be embedded in a transvenous cardiac lead in order to sense the endocardial acceleration signal. The originality of the approach consists of using an interposer and a lid, both made of conductive doped silicon to connect the device. The MEMS and the ASIC are attached on the silicon interposer and the silicon lid is bonded using eutectic AuSi ring. The electrical interconnection to the two conductor wires is obtained through the interposer and the lid using the conductivity of doped silicon. The system integration was performed at the wafer level. A test vehicle which allows characterizing the required technologies was designed and manufactured. A technical focus on the most important process steps for the integration is presented and discussed in this paper. This includes interconnection on doped silicon, dies on wafer bonding and wafer to wafer bonding. The hermeticity and biocompatibility encapsulation of the device is also addressed and a prototype which has been designed is described.
This paper presents a new strategy of packaging developed for medical applications which includes a sensor and an integrated circuit inside a hermetic silicon box that could be embedded in a cardiac lead in order to monitor the endocardial acceleration. The electronic components are placed on a silicon interposer wafer which was bonded by the eutectic AuSi with a silicon wafer lid containing cavities. Different metal stacks of the sealing ring including a barrier and Au have been studied. The gas content and hermeticity of the package were analyzed using Residual Gas Analysis (RGA) and biodegradation were tested in saline solution. The final silicon package was encapsulated with biocompatible materials that have high conformality deposition and act as good bi-directional barrier. Materials behavior that had been reported in literature as biocompatible and compatible with fabrication in standard clean rooms were studied. Finally, packaging materials were tested in cytotoxicity.
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