Jean-Yvon Jezequel

Study of the spatial resolution of a new 3D microfabrication process: the microstereophotolithography using a dynamic mask-generator technique

Abstract In order to manufacture new micromechanical components, a new 3D microfabrication technique called the ‘microstereophotolithography using a dynamic mask-generator’ process has been developed. This technique is based on the use of a liquid crystal display as dynamic mask-generator It obliged us to choose photopolymerizable chemical mixtures, specifically designed for microfabrication, that react to visible wavelengths. The chemical resin we used showed a main disadvantage. It contains an organic dye that undergoes photochemical bleaching. A precise control of the spatial resolution of the physico-chemical process happening during the photoreaction is required in order to manufacture small components. Then, the influence of photobleaching on the photopolymerization resolution has thus been investigated. An experimental study has been compared with a mathematical model describing the phenomenon and allowed to optimize the operating conditions of the microstereophotolitoography device we built, and to manufacture small three-dimensional objects made of a large number of complex layers with a resolution better than 5 μm.

Industrial photochemistry XXIV. Relations between light flux and polymerized depth in laser stereophotolithography

The stereophotolithography process allows a three-dimensional object to be built by layer-by-layer, space-resolved, light-induced polymerization of a liquid monomer into a solid polymer. The relationship between the light penetration depth in the photoreacting medium, the scanning speed of the laser beam on the surface of the resin and the laser power has been studied. Experimental measurements have been performed and compared with a kinetic model. Empirical laws of evolution of the polymerized depth vs. macroscopic parameters have also been determined allowing the optimal operating conditions in stereophotolithography to be defined.

Microphotofabrication of very small objects : Pushing the limits of stereophotolithography

Abstract Stereophotolithography (SPL) allows to manufacture 3D polymer parts directly from Computer Aided Design data files. Its principle is the space resolved polymerization of a resin by a laser. We first discuss the possibilities to make parts with a very high resolution. A first approach was to push the classical SPL process to its limits to get a resolution of about 30 micrometres. A second really innovating one was to modulate the light flux by a liquid crystal display and we obtained a resolution of 5 micrometres. Since the use of these parts is limited by the nature of photopolymers, we also developed a new process to make complex polymer/metal parts directly. It consists in making the part layer by layer by using three techniques: SPL, electrodeposit of copper and laser silver plating.