Laser deposition from a lava stone cup

We propose a procedure for the growth of thin films of organic and bio-molecules, which is based on MAPLE (Matrix Assisted Pulsed Laser Evaporation) and inspired by the laser cleaning technique. This procedure is MAPLE-like, meaning that the "evaporation", or better the ejection of the material to deposit, is not assisted by the matrix, but rather by the target-holder. The target-holder is basalt, a magmatic rock which is able to absorb the laser radiation used (1064 nm) thanks to its high content in iron oxides. A thin veil of solution that contains the molecule of interest is placed into the basalt cup, frozen and irradiated. The laser radiation reaches the bottom of the cup, where it is absorbed. The consequent increase in temperature generates the phase explosion of the overlying frozen matrix. This procedure can be used to obtain thin films from transparent matrices. Here we deposited the enzyme ?-glucosidase highly preserving its native conformation. The laser power used was under the ablation threshold of the basalt, so that only few fragments of the rock reached the substrate.