Rapid prototyping of microfluidic systems using two-photon lithography
Lölsberg, Jonas; Wessling, Matthias (Thesis advisor); Hecht, Stefan (Thesis advisor)
Book, Dissertation / PhD Thesis
In: Aachener Verfahrenstechnik series - AVT.CVT - chemical process engineering 10 (2021)
Page(s)/Article-Nr.: x, 118 Seiten : Illustrationen, Diagramme
Additive manufacturing is revolutionizing research and development activities as the pace for innovation increases with the fast formation of complex prototypes. Current lithography techniques prototype polymeric objects at the macro-, meso- and microscale with spatial resolutions spanning over several orders of magnitude. In this, the diffraction of light is limiting the resolution of linear optical lithography techniques. Two-photon lithography can even surpass the optical diffraction limit by confining nonlinear photon adsorption to an ellipsoid. The ability to control the movement of the ellipsoid in time and space enables additive polymerization inside a light-sensitive photoresist. In the present thesis, two-photon lithography is used to create truly three-dimensional microfluidic systems. The geometry of such systems manipulates the prevailing fluid dynamics and transport phenomena. To augment device functionality, even smaller prototyped objects are directly interfaced into the microfluidic channel using in situ two-photon lithography. These free-form objects reside tightly sealed and connected to the macroscopic world. The novel technique is demonstrated by continuous polyacrylonitrile coagulation that is forming single-digit micron fibers in an interfaced co-flow wet-spinning nozzle. Substantially smaller nanofibers are directly synthesised inside a horizontal-flow channel using in situ two-photon continuous-flow lithography. This continuous-flow lithography technique is extended to the real-time synthesis of complex free-standing porous microtubes inside a vertical-flow channel. The combined benefits of a controlled microfluidic environment with the precision of in situ two-photon lithography contributes to the generic formation of complex-shaped materials with rigorous control over the morphology and surface topology. The developed methodology is further transferred to investigate the advancement of the first continuous microfluidic cell-sorting device towards a thrombocyte bypass for extracorporeal membrane oxygenation. Within the cell-sorting device, whole blood with a clinical relevant hematocrit is sorted based on the joint effects of flow focusing and inertial lift forces resulting in lateral cell migration. The speed of migration is dependent on size and shape of the cellular components. The application of three-dimensional microfluidic systems in a clinical regulated environment demonstrates the potential and transferability of the developed methodology to a multitude of theoretical and practical problems in the natural sciences and technology.