LMI Seminar:

Nanoplasmonic and nanophotonic active devices

Prof. Uriel Levy

Department of Applied physics and the center for nanoscience and nanotechnology, The Hebrew University of Jerusalem

Wednesday November  9^th,  2022

13:00-14:00

Light refreshments and drinks will be served at 12:30

Auditorium 011, Engineering Classroom Building,  Faculty of Engineering, Tel-Aviv University

Abstract: We present our recent results related to active nanoplasmonic and nanophotonic devices. Several mechanisms for implementing active devices will be discussed. We will describe the demonstration of tunability in dielectric and metallic metasurfaces for diverse applications using tunability mechanism such as MEMS technology integrated with metasurfaces and the electro optic effect in lithium niobate integrated with metasurfaces, as well as the tunability of a metasurface by controlling an external medium. We also discuss the role of nanoscale structures in enhancing functionalities such as light emission and light detection. Nanophotonic devices with memory functionality will be discussed as well. Finally, we present how metalenses can be used for 3-D imaging.

Bio: Prof. Uriel Levy is the head of the nano-opto lab and the director of the center for nanoscience and nanotechnology at the Hebrew University, Jerusalem Israel. His research spans over diverse aspects of nanophotonics and light-matter interactions, with focus on device oriented research. Over the years, he pioneered several key concepts in nanophotonics, including silicon based photodetection in the short wave infrared (SWIR), nanoscale polarization optics, and the chip scale atomic vapor technology. His research covers both fundamentals of light-matter interactions, as well as diverse applications in imaging, communications, sensing, metrology, energy harvesting, memories, displays and other chip scale optoelectronic devices. Over the years, Prof. Levy published nearly 200 journal papers, presented his results in hundreds of invited talks and he holds dozens of patents. Prof. Levy is a fellow of OPTICA (formerly the optical society of America) and is the recipient of several notable prizes, including for example the Kaye innovation award, an ERC consolidator grant, and the Hebrew University President award for young Investigator. He holds a BSc in Physics and materials science from the Technion and a PhD in electro optics from Tel Aviv University. Prior to joining the Hebrew University, he spent nearly four years as a post graduate researcher in the University of California, San Diego.   Prof. Levy is also active in tech transfer. He is a co-founder of Trieye, developing CMOS based cost effective SWIR imaging solutions for the automotive industry and for other verticals

School of Mechanical Engineering Seminar

Wednesday, December 14, 2022 at 14:00
Wolfson Building of Mechanical Engineering, Room 206

Numerical analysis of the hemodynamics and performance of a miniature ventricular assist device

Yuval Gabso

           MSc of Moshe Rozenfeld

The use of axial percutaneous left ventricular assist devices (p-LVAD) in the clinical setting of acute heart failure has recently been significantly increased. Although these devices have improved the management, survival, and prognosis of many patients with acute of chronic heart failure, there is still high mortality and a wide burden of disease, mostly due to related thrombosis (blood clots) that can cause stroke, and hemolysis (rapture of blood cells) that can lead to anemia. p-LVADs designs with reduced blood trauma are likely to improve clinical outcomes and expand p-LVAD therapy to patients with less severe heart failure.

The present study investigated two configurations of p-LVAD designs, a floating impeller driven by magnetic levitation and a motor driven suction pump. The effects of the hub geometry on the hemodynamic characteristics, pump performance and blood damage were evaluated using CFD. It has been confirmed that assuming steady flow within a rotation frame approximates well the average flow of the transient case. Four different impellers (diameter of 5-6mm) were built and twenty cases were analyzed at different working conditions of pressure heads (60-80mmHg) and angular velocities (30-52kRPM). The numerical simulations used the Reynolds-Averaged Navier-Stokes approximation employing the SST turbulent model. Estimation of RBC hemolysis was conducted according to four different models (based on Kolmogorov length scale; and based on combinations of exposure time to shear stress above 425[Pa]). Probabilities for shear induced platelet activation (PDF) were estimated based on accumulated shear stresses along streamlines.

The results of the simulations reveal that the shape of the impeller’s hub has a great impact on the flow patterns, performance and the risk for blood damage. Impellers with a converging hub encourage recirculating flow and increase the residence time while impellers with an expanding hub have higher wall shear stress with less reversed flow regions. The suction pump has the best performance with efficiency of 19%, while the floating impeller reaches a maximal efficiency of 12% only. However, the high efficiency of the suction pump is achieved at the cost of increased risk of platelets activation. A strong correlation is also found between the angular velocity and the risk for hemolysis in all four models.

This study shed light on the effects of pump configuration on the performance and risk of blood damage, indicating the roles of the hub shape and angular velocity as dominant parameter. These findings can be utilized to improve future designs of p-LVAD.

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