Plasma-free bubble cavitation in water by a 2.9 μm laser for bioprinting applications

Abstract

We investigate the dynamics of the cavitation bubble induced by 2.9 μm mid-IR laser pulses (10 ns, 10–50 μJ), resulting in a plasma-free direct fast heating of water due to a strong vibrational absorption. We establish a direct correlation between the laser fluence (up to 6 J cm−2) and the maximum bubble radius (up to 200 μm). From experimental data, key parameters (threshold energy and internal pressure) can be retrieved by simulations including the water absorption saturation at 2.9 μm. At a fluence of 6 J cm−2, we obtain 13% of the laser energy converted to a bubble energy, and we can predict that operating at higher fluence >10 J cm−2 will lead to a maximum of 20% conversion efficiency. These results open the door to bioprinting using direct absorption of the laser radiation without additional absorber.