Unraveling of 2-photons polymerization in Direct Laser Writing by coupling in-situ diagnostic methods with high spatial and time resolution – 2PhotonInsight
Nowadays, there is a growing demand for compact and elaborate 3D microsystems to fullfill the requirements in various fields such as nanomechanic, nanophotonic, nanofluidic, nanomedecine or biology. Whereas different strategies have been successfully implemented for mass production of 2D/2.5D micro and nanostructures, fabrication of 3D micro and nanostructures is usually not trivial and required time-consuming multi-steps processes. In this context, additive manufacturing technology (AMT) is particularly attractive but suffers from a lack of spatial resolution. Thereby, two-photon stereolithography (TPS) appears of high interest since it makes possible in a unique step the fabrication of intricate 3D structures with features sizes as small as 100 nm. Besides, recent achievements regarding the writing speed have underlined the potential of TPS as a sub-micro scale additive manufacturing and confirmed its emerging role as a key enabling technology in a near futur. Nevertheless, contrary to standard AMT, TPS has not reached a sufficient level of maturity to allow value-added commercial applications, and even more surprising, its use is still limited to some academic communities.
Nowadays, in order to traverse the threshold of industrialization and favor TPS dissemination in all academic communities, one remaining challenge consists to develop and characterize functional materials compatible with the TPS process. Whereas we and other have very recently proposed innovative functional materials compatible with TPS, the impact of this fabrication process on the final properties have been scarcely investigated due to the complexity of the process. Indeed, contrary to most standard conventional photopolymerization applications such as UV curing and coating, TPS presents specific reaction conditions such as highly localized (< µm3), intense and short laser pulse excitation which limit its full investigation by conventional methods (FTIR, Raman, PhotoDSC,…). Besides, owing to the little amount of polymerized material, standard analysis such as HPLC are not possible. Finally, at these time and space scales, many phenomenons have to be taken in consideration such as molecular diffusion, optical aberration, local heating, post-polymerization and so on… Therefore so far, TPP’s studies have been mostly limited to the analysis of geometrical shape and size of the smallest features (called voxel) or of suspended lines in function of the writing fabrication parameters (exposure time and power).
In this context, 2PhotonInsight aims to unraveling the two photon polymerization (TPP) reaction occurring during the 3D direct laser writing process. In that purpose, a first task will consist to characterize the final properties of the material from a geometrical, chemical and mechanical point of view. To achieve this goal, conventionnal (SEM, Raman microspectroscopy) and novel approaches (laser vibrometry) will be performed. In a second task, the kinetic of the TPP photoreaction will be investigated. In that regard, one needs to propose method with time (ten to hundred of µs) and spatial (sub-µm) resolution compatible with the TPP reaction, therefore novel strategies based on fluorescent molecular probes sensitive to the viscosity will be attemped.
These two first steps will lead to a better understanding of the TPP reaction which is crucial to exert a better control on the processing route and achieve to build relationships between final properties of the materials and the conditions of fabrication.
Finally, in order to illustrate the interest of our approach, we will take advantage of the resulting knowledge to design well-characterized surface model for cell biology and to assess the impact of each fabrication parameter on the cell behavior.
Monsieur Arnaud SPANGENBERG (Institut de Science des Matériaux de Mulhouse - CNRS UHA)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
IS2M-CNRS UMR7361 Institut de Science des Matériaux de Mulhouse - CNRS UHA
Help of the ANR 249,600 euros
Beginning and duration of the scientific project: December 2016 - 48 Months