The crossed limbs stent graft technique is regularly employed to treat abdominal aortic aneurysm patients with unfavorable aneurysm necks or widely splayed common iliac arteries. This article numerically evaluates the hemodynamic performance of the crossed limbs strategy by analyzing numerical simulations and conducting experiments using two series of idealized bifurcated stent grafts with different cross angles and cross positions. Results demonstrated that the absolute helicity at outlets decreased with increased cross angles and increased with decreased cross positions. The time-averaged wall shear stress remained approximately unchanged, whereas the oscillating shear index and relative resident time decreased slightly when the cross angle increased and cross position decreased in iliac grafts. Additionally, both numerical and in vitro experimental results indicate the displacement force acting on the stent graft gradually increased as cross angles increased and cross positions decreased. Results further indicated that strip areas with a high oscillating shear index and high relative resident time, which may be vulnerable to thrombosis formation, exist along the outer surface of the iliac artery grafts. Given this information, the optimal crossed limbs configuration may contain a small cross angle and low cross position; however, low cross positions may increase the risk of migration.

Inferior vena cava filter (IVCF) implantation is a common method of thrombus capture. By implanting a filter in the inferior vena cava (IVC), microemboli can be effectively blocked from entering the pulmonary circulation, thereby avoiding acute pulmonary embolism (PE). Inspired by the helical flow effect in the human arterial system, we propose a helical retrievable IVCF, which, due to the presence of a helical structure inducing a helical flow pattern of blood in the region near the IVCF, can effectively avoid the deposition of microemboli in the vicinity of the IVCF while promoting the cleavage of the captured thrombus clot. It also reduces the risk of IVCF dislodging and slipping in the vessel because its shape expands in the radial direction, allowing its distal end to fit closely to the IVC wall, and because its contact structure with the inner IVC wall is curved, increasing the contact area and reducing the risk of the vessel wall being punctured by the IVCF support structure. We used ANSYS 2023 software to conduct unidirectional fluid–structure coupling simulation of four different forms of IVCF, combined with microthrombus capture experiments in vitro, to explore the impact of these four forms of IVCF on blood flow patterns and to evaluate the risk of IVCF perforation and IVCF dislocation. It can be seen from the numerical simulation results that the helical structure does have the function of inducing blood flow to undergo helical flow dynamics, and the increase in wall shear stress (WSS) brought about by this function can improve the situation of thrombosis accumulation to a certain extent. Meanwhile, the placement of IVCF will change the flow state of blood flow and lead to the deformation of blood vessels. In in vitro experiments, we found that the density of the helical support rod is a key factor affecting the thrombus trapping efficiency, and in addition, the contact area between the IVCF and the vessel wall has a major influence on the risk of IVCF displacement.

Blood flow condition may have influence upon the hydraulic conductivity of venous graft (Lp,vein) in an arterial bypass, then affecting the accumulation of low-density lipoproteins (LDLs) within the graft wall. To probe this possibility, we first measured in vitro the filtration rates of swine lateral saphenous vein segments under different flow rates, and the correlation of Lp,vein with wall shear stress (WSS) was then obtained. The experimental results showed that when WSS was very low, Lp,vein would increase drastically with WSS from 1.16 ± 0.15 × 10−11 m/s Pa at 0 dyn/cm2 to 2.17 ± 0.20 × 10−11 m/s Pa at 0.7 dyn/cm2, then became constant of approximately 2.33 × 10−11 m/s Pa as the WSS increased further. Based on the experimental results, we assumed three different cases of Lp,vein and numerically simulated the LDLs transport in an arterial bypass model with venous graft. Case A: Lp,vein = 2.33 × 10−11 m/s Pa; Case B: Lp,vein = 1.16 × 10−11 m/s Pa (static condition with WSS of 0); Case C: Lp,vein was shear dependent. The simulation showed that the deposition/accumulation of LDLs within the venous graft wall in Case A was greatly enhanced when compared with that in Case B. However, the LDL accumulation in the graft wall was similar for Case A and Case C. Our study, therefore, indicates that when the venous graft was implanted as a bypass graft, the Lp,vein might remain nearly constant along its whole length except for very few areas where the value of WSS was extremely low (less than 0.7 dyn/cm2) and the effects of Lp,vein modulated by blood flow on LDL transport may be neglected.

A rapid, sensitive, and low-damage method for isolating circulating tumor cells (CTCs) is crucial for cancer research. This study, based on dielectrophoresis (DEP) and finite element modeling, investigates multitarget cell separation from blood on microfluidic chips. The effects of electrode shape, dielectric conductivity, and flow rate on cell movement and separation efficiency were analyzed. The results showed optimal separation with a 90 degrees electrode angle, 1.5 V applied voltage, and a 1:3 inlet flow rate ratio. This study provides valuable insights for optimizing DEP-based microfluidic devices to improve multitarget cell separation efficiency and purity.

Separating target particles (e.g., bacteria) from complex media is critical to preventing matrix interference in the detection and analysis of target substances. However, existing techniques still face challenges in improving throughput for the separation of bacteria-sized particles. To address this, we present a novel width-expanding spiral microchannel designed for continuous, high-throughput separation of bacteria-sized particles from larger particles. The separation principle and the effect of width variation on separation performance were assessed through numerical simulations and experimental tests. Numerical results indicate that, compared to a constant-width microchannel, a width-expanding microchannel exhibits a lower Dean flow distribution due to the gradually increasing aspect ratio, resulting in delayed migration of smaller particles due to Dean flow. This migration lag can be compensated by increasing the operating flow rate. Fluorescent microsphere experiments demonstrated that the width-expanding microchannel achieved 99.20% and 96.70% separation efficiencies for 1 μm microspheres from mixtures containing 7 μm and 10 μm microspheres, respectively, at flow rate of 170 µL/min, thereby surpassing the performance of existing technologies. Considering separation performance, pressure drop, and processing throughput, the width-expanding microchannel ensures both high separation efficiency and lower pressure drops, enabling higher-throughput operation. This innovative design holds significant promise for enhancing bacterial isolation from infected blood and reducing the time required for bacterial pretreatment.