Study of the laser forward transfer for the preparation of miniaturized biosensors

THESIS SUMMARY:The possibility to print tiny amounts of functional materials in a controllable way is of interest in a large number of applications, for instance in the manufacturing of organic electronics, in the deposition of artificial organs (the so-called organ printing), or in the fabrication of miniaturized devices in areas like biosensing. This has prompted the development of microfabrication techniques capable of depositing such functional materials.The present work is focused on one of these techniques, particularly on a laser-based direct-writing technique called laser-induced forward transfer (LIFT), in which laser pulses are used to deposit material from a donor film to a receptor substrate. This technique is especially interesting due to the possibility that it offers to print droplets of solutions containing functional materials with a high resolution. Moreover, it has additional advantages such as the capability to work in air (at atmospheric pressure and room temperature), the fact that it is a non-contact technique that avoids contamination problems, and the possibility to combine it with laser micromachining.In this work, a complete study of the LIFT of liquid solutions is performed in order to achieve a better understanding of this technique and to find the optimum printing conditions. Such study comprises the analysis of the role that some of the most important experimental parameters have on the printed droplets, as well as the analysis of the mechanisms involved in the ejection and deposition of material through LIFT. This is accomplished by means of both the morphological characterization of the printed droplets at different conditions and the time-resolved imaging of the LIFT process, including the ejection and transport of liquid, as well as the deposition of liquid on the receptor substrate. The present work has provided a complete picture of the LIFT process: the experimental conditions adequate for droplet printing have been set up, and the mechanisms responsible for the generation of droplets have been unveiled. The feasibility of the technique for protein printing has also been demonstrated. Moreover, it has also been found that the preparation of the liquid film in thin form is the major problem that the technique faces. This last aspect has motivated the research of a new technique capable of dispensing with the preparation of the liquid film. This novel technique has been successfully developed and tested in this thesis work.EXTRACTE EN CATALA:La present tesi esta centrada en una tecnica d'escriptura directa anomenada transferencia induida per laser (amb angles laser-induced forward transfer, o LIFT), en la qual s'utilitzen polsos laser per dipositar material des d'una pel·licula donadora a un substrat receptor. Aquesta tecnica es especialment interessant degut a la possibilitat que ofereix per imprimir, amb una gran resolucio, gotes de solucions que contenen materials funcionals. A mes a mes, te avantatges addicionals com ara la capacitat de treballar sense buit i a temperatura ambient, el fet de ser una tecnica que evita problemes de contaminacio al no estar en contacte la pel·licula donadora amb el substrat receptor, i finalment al poder-la combinar amb altres tecniques com ara la micromecanitzacio amb laser.En aquest treball es presenta un estudi complet de la LIFT per tal d'aconseguir-ne una millor comprensio aixi com trobar les condicions optimes d'impressio. Els materials dipositats han estat sempre solucions liquides. L'estudi presentat compren l'analisi dels efectes que alguns dels parametres mes importants de la tecnica tenen en la morfologia de les gotes transferides, aixi com l'analisi dels mecanismes involucrats en l'ejeccio i diposit de material a traves de la LIFT. Aixo s'ha aconseguit mitjancant la caracteritzacio morfologica del material transferit a diferents condicions, aixi com utilitzant l'adquisicio rapida d'imatges del proces d'ejeccio de material i de diposit. Aquest treball ha permes obtenir una imatge completa del proces de la LIFT: s'han determinat les condicions adequades per la impressio de gotes, i els mecanismes per a la generacio de gotes s'han desxifrat. La viabilitat de la tecnica per a la impressio de proteines tambe s'ha demostrat. A mes a mes, s'ha trobat que la preparacio de la pel·licula liquida per a la LIFT es el principal inconvenient que te aquesta tecnica. Aquest aspecte ha motivat la recerca d'una nova tecnica capac d'evitar la pel·licula liquida. Aquesta nova tecnica s'ha desenvolupat i provat satisfactoriament en aquest treball.