A simple passive microfluidic device that continuously separates microparticles is presented. Its development is motivated by the need for specific size micro perfluorocarbon (PFC) droplets to be used for a novel gas embolotherapy method. The device consists of a rectangular channel in which inertial lift forces are utilized to separate particles in lateral distance. At the entrance of the channel, particles are introduced at the center by focusing the flow from a center channel with flow from two side channels. Downstream, large particles will occupy a lateral equilibrium position in shorter axial distance than small particles. At the exit of the channel, flow containing large particles is separated from flow containing small particles. It is shown that 10.2-μm diameter microspheres can be separated from 3.0-μm diameter microspheres with a separation efficiency of 69-78% and a throughput in the order of 2 ·10⁴ particles per minute. Computational Fluid Dynamics (CFD) calculations were done to calculate flow fields and verify theoretical particle trajectories. Theory underlying this research shows that higher separation efficiencies for very specific diameter cut-off are possible. This microfluidic channel design has a simple structure and can operate without external forces which makes it feasible for lab-on-a-chip (LOC) applications.

Gas embolotherapy is achieved by locally vaporizing microdroplets through acoustic droplet vaporization (ADV), which result in bubbles that are large enough to occlude blood flow directed to tumors. Endothelial cells, lining blood vessels, can be affected by these vaporization events leading to cell injury and cell death. An idealized monolayer of endothelial cells was exposed to ADV using a 3.5 MHz transducer and dodecafluoropentane droplets. Treatments included insonation pressures that varied from 2 to 8 MPa (rarefactional), and pulse lengths that varied from 4 to 16 input cycles. The generated bubble cloud was directly dependent on pressure, but not on pulse length. Cellular damage increased with increasing bubble cloud size, but was limited to the bubble cloud area. These results suggest that vaporization near the endothelium may impact the vessel wall, an effect that could be either deleterious or beneficial depending on the intended overall therapeutic application.

A fundamental study to characterize the flow around an oscillating cylinder in a pulsatile flow environment is investigated. This work is motivated by a new proposed design of the total artificial lung (TAL), which is envisioned to provide better gas exchange. The Navier-Stokes computations in a moving frame of reference were performed to compute the dynamic flow field surrounding the cylinder. Cylinder oscillations and pulsatile free-stream velocity were represented by two sinusoidal waves with amplitudes A and B and frequencies ω(c) and ω, respectively. The Keulegan-Carpenter number (K(c)=U(o)∕Dω(c)) was used to describe the frequency of the oscillating cylinder while the pulsatile free-stream velocity was fixed by imposing ω∕K(c)=1 for all cases investigated. The parameters of interest and their values were amplitude (0.5D

Hepatocellular carcinoma is the third leading cause of cancer-related deaths worldwide. Many patients are not eligible for curative therapies, such as surgical resection of the tumor or a liver transplant. Transarterial embolization is one therapy clinically used in these cases; however, this requires a long procedure and careful placement of an intraarterial catheter. Gas embolization has been proposed as a fast, easily administered, more spatially selective, and less invasive alternative. Here, we demonstrate the feasibility and efficacy of using acoustic droplet vaporization to noninvasively generate gas emboli within vasculature. Intravital microscopy experiments were performed using the rat cremaster muscle to visually observe the formation of occlusions. Large gas emboli were produced within the vasculature in the rat cremaster, effectively occluding blood flow. Following these experiments, the therapeutic efficacy of gas embolization was investigated in an ectopic xenograft model of hepatocellular carcinoma in mice. The treatment group exhibited a significantly lower final tumor volume (ANOVA, p = 0.008) and growth rate than control groups – tumor growth was completely halted. Additionally, treated tumors exhibited significant necrosis as determined by histological analysis. To our knowledge, this study is the first to demonstrate the therapeutic efficacy of gas embolotherapy in a tumor model.