Parametric geometry modeling of the carotid artery bifurcation: the need for new flow metrics
Although well established correlations now exist between regions of reversed flow and sites of arterial disease [1], little evidence is available for methodologies that systematically compare how geometrical differences affect such relationships. Drawing on techniques developed in aerodynamic design, a parametric tuning-fork geometry model of the carotid artery bifurcation - based on the glass models described in [2] - is here employed to investigate the impact of bulb size and the angle of the internal carotid artery (ICA) on time-averaged shear stress. Since we seek to directly compare the effect of varying these geometric parameters, we demonstrate the need for a new metric, the integral of negative mean shear stress (INMSS), to highlight the stronger correlation between the extent of reversed flow and bulb width relative to the angle of the ICA.
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Fully Integrated Bidirectional CMOS-MEMS Flow Sensor With Low Power Pulse Operation
Leveraging More-than-Moore technology, we demonstrate an integrated CMOS MEMS flow sensor via a very compact system on chip (SoC) that can sense the bidirectional N2 gas flow. Our SoC features a very low-noise instrumentation amplifier that is implemented on a CMOS wafer and serves as a readout integrated circuit for a thermoresistive micro-calorimetric flow sensor which is fabricated on a MEMS wafer. A compact heterogeneous integration is achieved by combining the two wafers via the proprietary InvenSense AlN process. The measured sensitivity of our CMOS MEMS flow sensor is 98 mV/sccm which is three times better than the state-of-the-art counterpart. The flow range measured by our SoC is from −26 to 26 m/s (from −50 to 50 sccm). Moreover, the pulsed heater operation makes this proposed SoC flow sensor a very low power (<9 mW) and, thus, a promising candidate for the Internet-of-Things applications in smart home/green buildings.