Penetration of impact-induced jets into skin-simulating materials

TL;DR

This paper investigates the penetration characteristics of impact-induced liquid jets into skin-simulating materials, revealing that such jets penetrate deeper than laser-induced jets at similar velocities and proposing a shear deformation model to explain the mechanism.

Contribution

It introduces an impact-induced jet system for needle-free injection, demonstrating its superior penetration depth and developing a shear deformation model for jet penetration.

Findings

Impact-induced jets achieve greater penetration depth than laser-induced jets at similar velocities.

Penetration depth remains constant regardless of offset distance D.

The shear deformation model accurately predicts penetration behavior.

Abstract

This study compares the penetration characteristics of impact-induced jets with those of laser-induced jets, focusing on the underlying penetration mechanism rather than device performance for needle-free injection. Using an impact-induced jet system capable of ejecting a highly focused liquid jet at high speed without the use of lasers, we examine jet penetration into skin-simulating materials. Unlike conventional needle-free injectors that produce diffused liquid jets, the impact-induced method generates a highly focused jet that limits the injected area, thereby reducing invasiveness. Comparative experiments with laser-induced jets show that, even at similar jet tip velocities, impact-induced jets achieve greater penetration depth. The penetration depth remains constant regardless of the offset distance D from the target, owing to the high and nearly uniform velocity of the cylindrical jet root region, indicating that penetration is governed by the cylindrical jet structure. Furthermore, we systematically vary the liquid viscosity, jet inertia, and elastic modulus of the skin-simulating material. To account for cylindrical liquid jet penetration, a shear deformation model is proposed, in which the jet kinetic energy is dissipated through deformation of the gelatin. The model shows good agreement with experimental results and provides a unified physical basis for liquid jet penetration.