High-Throughput, Semi-Autonomous Measurement of Cavitation-Mediated Material Breakage

Abstract

Engineered microbubbles can be acoustically driven to cavitate against a substrate to produce localized erosion and fragmentation. This mechanical action has therapeutic applications in the treatment of biomineralizations, such as in urinary stone disease. However, current methods for quantifying the mechanical action of cavitation on a substrate are slow or imprecise. In this paper, we describe the design of a device that applies calibrated pressures to microbubbles engineered to target a calcium-containing hydroxyapatite substrate under physiological conditions and quantifies the result via an automated submerged mass measurement with high precision and low drift. Measurements of microbubble-mediated mass loss were observed to be linear with time, with variance that was comparable to the resolution of the instrument. The rate of mass loss with microbubbles present was 5.5-fold greater than in the absence of microbubbles. This research instrument captures the essential mechanical and physiological features of in vivo microbubble-mediated erosion and fragmentation of urinary stones and has been used to optimize the parameters of this treatment in a clinical trial for a promising new approach to the treatment of nephrolithiasis. In addition to clinically relevant therapeutic applications, this approach will contribute to broader understanding of acoustic cavitation against a substrate.