Twisted shock waves enable ballistic microparticle manipulation

The ability to control the motion of microscopic objects in liquids is important for applications ranging from microfluidics to the study of fast hydrodynamic processes. However, conventional optical and acoustic manipulation techniques rely mainly on continuous forcing, limiting access to impulsive dynamics on nanosecond timescales. Here we show that spiral-shaped nanosecond laser pulses focused into a thin liquid layer generate twisted shock waves with tunable angular momentum and peak pressures on the order of gigapascals. Time-resolved shadowgraphy and two-dimensional hydrodynamic simulations independently show the same dependence on the spiral geometry, revealing that the angular momentum can be controlled through the excitation shape. We further show that a 10- μ m polystyrene particle exhibits loop-like ballistic motion on nanosecond timescales, with complementary measurements along two orthogonal directions supporting this interpretation. These results provide an impulse-driven approach for controlling and probing ultrafast particle dynamics in liquids, with potential applications in high-pressure microfluidics, microrheology, and short-time hydrodynamics.