Population aging is a worldwide phenomenon, but its impact on Qatar is unique. The proposed system aims at comprehensive and integrated vital signs (ECG, Saturation of Arterial Oxygen (SpO2), BP and Heart rate (HR)) monitoring using a wearable sensor platform without professional involvements or interfering the elderly's everyday activities. A novel wireless physiological sensor node with single highly-integrated board has been specifically designed and fabricated ( Fig.1(a) ). The new board comprises of a MCU, ECG analog front-end, LED driver and brightness adjustment circuit for photoplethysmograph (PPG) measurement, a CC2420 chip for wireless communication and a FTDI FT232RL chip for MCU programming and real-time debugging. A miniaturized wireless gateway was also designed ( Fig.1(b) ) to wirelessly receive the data from sensor node and further relay to the PC for ongoing research on ECG denoising and arrhythmia classification.

A novel MEMS-based electrode has been designed and fabricated for ECG measurement as shown in Fig.2 . Compared with conventional ECG electrodes, micromachined electrode is more comfortable; no direct contact of gel with the human skin and imposes no side effects to human for continuous and long term measurement. A unique characteristic feature of the proposed electrode is that the microneedle array is made of heavily doped silicon, which is electrically conductive and eliminates the requirement to dope Ag/AgCl or metal layer on the microneedles for electric contact. The microneedles can directly pierce through the outer skin surface, lowering the electrode-skin-electrode impedance (ESEI) and eliminating the need for skin preparation which, is prerequisite for wet electrode. For long-term monitoring, mechanical failure of micro-needles may accidentally happen due to the axial loading during insertion process or transverse loading during the measurement. As a result, the broken silicon needles will become debris in the skin, which attracts healthy concern for the user. Therefore, critical buckling loads for fabricated micro-needle were investigated using both theoretical estimation and ANSYS simulation. The results show that the critical buckling load is much larger than theoretical insertion force thereby the buckling problem will not occur during the insertion process.

This work is supported by Qatar National Research Funding (QNRF) under the grant NPRP 09-292-2-113.


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