Figure 1

(A(1)) Schematic represents the investigational device that comprises a conventional Langevin ultrasound transducer coupled via an aluminum waveguide to a (A(2-3)) 21G hypodermic needle connected to a 10 mL syringe. The geometry permits connecting virtually any pressure source to the needle. (B(1)) Numerical simulation result representing the x-component of the time-average acoustic intensity evaluated on the xy-plane coincident with the needle center axis and (B(2)) on a line adjacent to the outer needle surface, starting from the needle tip and ending at the waveguide-needle attachment. These results demonstrate localization of sound energy at the very tip of the needle, more than double the intensity calculated elsewhere. (C(1)) The cavitation activity is highly concentrated at the needle tip, as supported by (C(2)) the projected spatial probability of cavitation in deionized water ([\(\text{O}_2\)] \(5.8 \, {\text {mg}} \; {\text{L}}^{-1}\)). (D–F) Temporally we observed a cavitation onset after which the inertial cavitation events continued in an uninterrupted manner. (G) The applied ultrasound induced peak velocities up to \(5 \, {\text {m}} \; {\text{s}}^{-1}\) and (H) acceleration of the bubble and water boundary that was equivalent to 20,000 G. The results demonstrate that a conventional medical needle can be converted into a highly controlled, ultrasonically functionalized instrument with significant NLU phenomena concentrated at the very tip of the needle.