*2.3.3. Drawbacks of MAPLE*

diameter and some large micronic particles. At 0.7 J/cm2

*2.3.2. Advantages of material deposition via MAPLE*

then uniformly deposited on the substrate.

NaOH, pH 7.5 (Reproduced with permission from Ref. [92]).

the transfer process.

micrometric particles, caused by the droplet expulsion from the target surface as a result of explosive evaporation or spallation mechanisms [88, 89] termed cold laser ablation [90, 91].

20 Applications of Laser Ablation - Thin Film Deposition, Nanomaterial Synthesis and Surface Modification

MAPLE was developed to surmount the difficulties in solvent‐based coating technologies such as inhomogeneous films, inaccurate placement of material, and intricate or erroneous thickness control. The process utilizes a low fluence pulsed UV laser and a frozen target consisting of a dilute mixture of the material to be deposited and a high vapour‐pressure solvent. The low fluence laser pulse interacts mainly with the volatile solvent, causing its evaporation. During the process, the solute desorbs intact, that is, without any significant decomposition, and is

‐ It enables the thin film deposition from a large amount of organic materials, such as polymers,

‐ It is a non‐contact deposition technique free of pollution risks for the thin films. The molecular composition and structure of the material that is deposited by MAPLE are preserved during

**Figure 17.** FTIR images of (a) laser immobilized RNase A obtained by the irradiation of 1 wt% frozen composite RNase A target, and the drop‐cast samples of (b) initial and (c) final MAPLE target solutions of RNase A in buffer HEPES–

In support of this assertion, we give the FTIR spectra for a RNase A enzyme thin film (**Figure 17a**), for drop‐cast of the initial RNase A solution used to prepare MAPLE targets (**Figure 17b**) and for the final RNase A solution, collected from the target holder after the

proteins, enzymes and combination of organic‐inorganic materials.

(**Figure 16c**), the film is covered by

The solvent has to be UV absorbing, therefore the choice is limited and in many cases very difficult.

In order to obtain perfect transfer of the organic material from the target to the substrate, a process optimization procedure is mandatory. Laser beam fluence, repetition rate, and pressure inside the reaction chamber have to be tweaked for each new material to be deposited.

Toxic, volatile solvents are often the only choice for target preparation.
