An ultrasonically actuated needle promotes the transport of nanoparticles and fluids

Abstract

Non-invasive therapeutic ultrasound (US) methods, such as high-intensity focused ultrasound (HIFU), have limited access to tissue targets shadowed by bones or presence of gas. This study demonstrates that an ultrasonically actuated medical needle can be used to translate nanoparticles and fluids under the action of nonlinear phenomena, potentially overcoming some limitations of HIFU. A simulation study was first conducted to study the delivery of a tracer with an ultrasonically actuated needle (33 kHz) inside a porous medium acting as a model for soft tissue. The model was then validated experimentally in different concentrations of agarose gel showing a close match with the experimental results, when diluted soot nanoparticles (diameter < 150 nm) were employed as delivered entity. An additional simulation study demonstrated a threefold increase in the volume covered by the delivered agent in liver under a constant injection rate, when compared to without US. This method, if developed to its full potential, could serve as a cost effective way to improve safety and efficacy of drug therapies by maximizing the concentration of delivered entities within, e.g., a small lesion, while minimizing exposure outside the lesion.

Efficient modeling of sharp-edge acoustofluidics

“…The herein introduced Hybrid modeling approach can be used to aid the emerging field of sharp-edge acoustofluidics. In the latter, sharp-edge structures such as needles or wedges in microfluidic devices are excited with ultrasound for a wide range of applications, ranging from propulsion of microrobots [48][49][50] and enhanced drug delivery [27] to advanced lab-on-a-chip technology involving sharp-edge-based micropumps and micromixers [3,8,9,[12][13][14]51].…”

“…Sharp-edge acoustofluidics has been successfully modeled in several studies using the Fully Viscous approach, but typically in 2D [4,13,25,26] and under further simplifications, such as assuming a periodicity across the device [3], using systems at low frequencies with the acoustic wavelength larger than the system (subwavelength system) [2,5,27], or exploiting symmetries [28]. Under these simplified conditions, a few studies featured the direct numerical simulations that revealed the threshold amplitude of the oscillatory excitation velocity at which the perturbation-based computation of the acoustic streaming near a sharp edge fails [2,5,29].…”