Hemodynamic performance evaluation of neonatal ECMO double lumen cannula using fluid-structure interaction.

Extra corporeal membrane oxygenation (ECMO) is an artificial oxygenation facility, employed in situations of cardio-pulmonary failure. Some diseases i.e., acute respiratory distress syndrome, pulmonary hypertension, corona virus disease (COVID-19) etc. affect oxygenation performance of the lungs thus requiring the need of artificial oxygenation. Critical care teams used ECMO technique during the COVID-19 pandemic to support the heart and lungs of COVID-19 patients who had an acute respiratory or cardiac failure. Double Lumen Cannula (DLC) is one of the most critical components of ECMO as it resides inside the patient and, connects patient with external oxygenation circuit. DLC facilitates delivery and drainage of blood from the patient's body. DLC is characterized by delicate balance of internal and external flows inside a limited space of the right atrium (RA). An optimal performance of the DLC necessitates structural stability under biological and hemodynamic loads, a fact that has been overlooked by previously published studies. In the past, many researchers experimentally and computationally investigated the hemodynamic performance of DLC by employing Eulerian approach, which evaluate instantaneous blood damage without considering blood shear exposure history (qualitative assessment only). The present study is an attempt to address the aforementioned limitations of the previous studies by employing Lagrangian (quantitative assessment) and incorporating the effect of fluid-structure interaction (FSI) to study the hemodynamic performance of neonatal DLC. The study was performed by solving three-dimensional continuity, momentum, and structural mechanics equation(s) by numerical methods for the blood flow through neonatal DLC. A two-way coupled FSI analysis was performed to analyze the effect of DLC structural deformation on its hemodynamic performance. Results show that the return lumen was the most critical section with maximum pressure drop, velocity, shear stresses, and blood damage. Recirculation and residence time of blood in the right atrium (RA) increases with increasing blood flow rates. Considering the structural deformation has led to higher blood damage inside the DLC-atrium system. Maximum Von-Mises stress was present on the side edges of the return lumen that showed direct proportionality with the blood flow rate.

Fabrication of Low-Cost Resistance Temperature Detectors and Micro-Heaters by Electrohydrodynamic Printing.

EHD printing is an advanced deposition technology that is commonly utilized for the direct manufacture of electrical devices. In this study, meander-type resistive electrodes consisting of silver nanoparticles were printed directly on rigid glass and flexible polyethylene terephthalate (PET) substrates. High-resolution patterns of ≈50 µm linewidth were successfully printed on untreated surfaces utilizing a bigger nozzle of 100 µm inner diameter after improving the experimental settings. The manufactured electrodes were evaluated and used as Resistance Temperature Detectors (RTDs) and micro-heaters in a systematic manner. The temperature sensors performed well, with a Temperature Coefficient of Resistivity (TCRs) of 11.5 ×10-3/°C and 13.3 ×10-3/°C, for glass and PET substrates, respectively, throughout a wide temperature range of 100 °C and 90 °C. Furthermore, the RTDs had a quick response and recovery time, as well as minimal hysteresis. The electrodes' measured sensitivities as micro-heaters were 3.3 °C/V for glass and 6.8 °C/V for PET substrates, respectively. The RTDs were utilized for signal conditioning in a Wheatstone bridge circuit with a self-heating temperature of less than 1 °C as a practical demonstration. The micro-heaters have a lot of potential in the field of soft wearable electronics for biomedical applications, while the extremely sensitive RTDs have a lot of potential in industrial situations for temperature monitoring.

Analysis of Passive Mixing in a Serpentine Microchannel with Sinusoidal Side Walls.

Sample mixing is difficult in microfluidic devices because of laminar flow. Micromixers are designed to ensure the optimal use of miniaturized devices. The present study aims to design a chaotic-advection-based passive micromixer with enhanced mixing efficiency. A serpentine-shaped microchannel with sinusoidal side walls was designed, and three cases, with amplitude to wavelength (A/λ) ratios of 0.1, 0.15, and 0.2 were investigated. Numerical simulations were conducted using the Navier⁻Stokes equations, to determine the flow field. The flow was then coupled with the convection⁻diffusion equation to obtain the species concentration distribution. The mixing performance of sinusoidal walled channels was compared with that of a simple serpentine channel for Reynolds numbers ranging from 0.1 to 50. Secondary flows were observed at high Reynolds numbers that mixed the fluid streams. These flows were dominant in the proposed sinusoidal walled channels, thereby showing better mixing performance than the simple serpentine channel at similar or less mixing cost. Higher mixing efficiency was obtained by increasing the A/λ ratio.