  Illuminating a water solution with a focused continuous wave laser produces a
strong local heating of the liquid that leads to the nucleation of bubbles,
also known as thermocavitation. During the growth of the bubble, the
surrounding liquid is expelled from the constraining microfluidic channel
through a nozzle, creating a jet. The characteristics of the resulting liquid
jet was imaged using ultra-fast imaging techniques. Here, we provide a
phenomenological description of the jet shapes and velocities, and compare them
with a Boundary Integral numerical model. We define the parameter regime,
varying jet speed, taper geometry and liquid volume, for optimal printing,
injection and spray applications. These results are important for the design of
energy-efficient needle-free jet injectors based on microfluidic
thermocavitation.
