Abstract
The potential to deposit minute amounts of material from a donor to an acceptor substrate at precise locations makes laser-induced forward transfer (LIFT) a frequently used tool within different research fields, such as materials science and biotechnology. While many different types of LIFT exist, each specialized LIFT application is based on a different underlying transfer mechanism, which affects the to-be-transferred materials in different ways. Thus, a characterization of these mechanisms is necessary to understand their limitations. The most common investigative methods are high-speed imaging and numerical modeling. However, neither of these can, to date, quantify the material deposition. Here, analytical solutions are derived for the contact-based material deposition by LIFT, which are based on a previously observed equilibrium state. Moreover, an analytical solution for the previously unrecognized ejection-based material deposition is proposed, which is detectable by introducing a distance between the donor and acceptor substrates. This secondary mechanism is particularly relevant in large scale production, since each deposition from a donor substrate potentially induces a local distance between the donor and acceptor substrates.
Highlights
One of the earliest reports of a laser-induced material deposition demonstrated the transfer of ink from a substrate toward a recording medium [1]
We previously showed that the material deposition through combinatorial LIFT (cLIFT) is mainly driven by the expansion of the sacrificial polyimide layer during laser irradiation and can be divided into four steps (Figure 1): (a) minor deformation of the polyimide after initial laser irradiation; (b) bell-shaped expansion of the polyimide in normal direction of the surface at a given time with a continuously decreasing expansion rate; (c) established stable contact with the acceptor due to the expanded polyimide with no further polyimide expansion; (d) relaxation of the polyimide layer and donor substrate material deposition after finished laser irradiation
Since the polyimide is the main driver of the contact-based material deposition within the cLIFT, a characterization of the observed expansion behavior has to be proposed to predict the material deposition
Summary
One of the earliest reports of a laser-induced material deposition demonstrated the transfer of ink from a substrate toward a recording medium [1]. The term LIFT is used to describe any process in which material is transferred from a donor to an acceptor substrate through laser irradiation (in the lasing direction). An interesting approach to transfer delicate materials is the dynamic release layer, LIFT [15]. This process utilizes a sacrificial intermediate layer as an absorbent to protect the donor substrate from the laser irradiation. The ablation of the metal layer potentially contaminates the transferred material To avoid such contamination, sacrificial polymer layers were introduced. Only liquid materials can be transferred through the BA LIFT, and the thick isolating polyimide layer has usually a set absorption spectrum
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