Laser-induced Forward Transfer of Liquids for Miniaturized Biosensors Preparation

Direct-writing techniques are adequate tools for rapid prototyping of diverse materials, since they avoid the usage of moulds or masks. Among them, laser-induced forward transfer (LIFT) has become a promising tool for rapid prototyping of microdevices due to the high focusing power of lasers, which provides a high resolution, and also to their non-contact and orifice-free nature, which avoids clogging and thus allows working with a wide range of materials. This makes LIFT an appropriate tool for biosensors preparation. In this article, immunoglobulin (IgG) microarrays were prepared through LIFT varying the laser pulse energy. It was found that there exists a minimum energy threshold, E-min, below which no material is deposited. Moreover, an analysis of the droplets volumes revealed a linear dependence of this parameter with the laser pulse energy, what allowed finding the existence of an energy density threshold, which is considered to be the threshold to generate an impulsion on the liquid film that only results in droplet ejection when the total energy overcomes E-min. Finally, the bioactivity of the transferred proteins was tested, showing no loss of their activity along the whole laser pulse energy range.