Laser-induced Microparticle Impact Experiments on Viscoelastic Gels*

High-velocity impact testing is used to study fundamental aspects of materials behavior under high strain rates as well as in applications ranging from micrometeorite detection to the development of novel drug delivery platforms. In this work, we study the high-velocity micro-particle impact response of viscoelastic gels, including hydrogels and synthetic polymer gels with non-aqueous solvents. In an all-optical laser-induced projectile impact test, micro-particles are accelerated through a laser ablation process. Depending on the laser energy, particles reach speeds up to 1 km/s in free space. Steel and silica particles are monitored during impact with an ultrahigh-speed multi-frame camera that can record up to 16 images with time resolution of each frame as short as 5 ns. We present images and movies capturing individual particle impact and penetration in gels and discuss the observed dynamics under a typical strain rate of 10⁸ s^-1. The results can provide direct input for modeling of high-velocity impact responses and high strain rate deformation in gels and other soft materials.