Plasma free bubble cavitation in water by a 2.9 {\mu}m laser for bioprinting applications

TL;DR

This study explores plasma-free cavitation bubbles in water induced by 2.9 μm laser pulses, revealing efficient energy conversion and potential for bioprinting without additional absorbers.

Contribution

It demonstrates the direct correlation between laser fluence and bubble size, and models energy conversion efficiency for bioprinting applications.

Findings

Maximum bubble radius of 200 μm at high fluence

13% laser energy conversion to bubble energy at 6 J/cm^2

Predicted 20% conversion efficiency at >10 J/cm^2

Abstract

We investigate the dynamics of the cavitation bubble induced by 2.9 {\mu}m mid-IR laser pulses (10 ns, 10-50 {\mu}J) 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 {\mu}m). From experimental data, key parameters (threshold energy, internal pressure) can be retrieved by simulations including the water absorption saturation at 2.9 {\mu}m. 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. This results open the door to bioprinting applications using direct absorption of the laser radiation without any additional absorber.