Abstract
Femtosecond laser based 3D nanolithography is a powerful tool for fabricating various functional micro- and nano-objects. In this work we present several advances needed to push it from the laboratory level use to the industrial production lines. First, linear stage and galvo-scanners synchronization is employed to produce stitch-free mm-sized structures. Furthermore, it is shown that by varying objective numerical apertures (NA) from 1.4 NA to 0.45 NA, voxel size can be tuned in the range from sub μm to tens of mm, resulting in structuring rates between 1809 μm3/s and 313312 μm3/s at 1 cm/s translation velocity achieved via simultaneous movement of linear stages and scanners. Discovered voxel/throughput scaling peculiarities show good agreement to ones acquired with numerical modeling. Furthermore, support-free 3D printing of complex structures is demonstrated. It is achieved by choosing pre-polymer that is in hard gel form during laser writing and acts as a dissolvable support during manufacturing. All of this is combined to fabricate micromechanical structures. First, 1:40 aspect ratio cantilever and 1.5 mm diameter single-helix spring capable of sustaining extreme deformations for prolonged movement times (up to 10000 deformation cycles) are shown. Then, free-movable highly articulated intertwined micromechanical spider and squids (overall size up to 10 mm) are printed and their movement is tested. The presented results are discussed in the broader sense, touching on the stitching/throughput dilemma and comparing it to the standard microstereolithography. It is shown where multiphoton polymerization can outpace standard stereolithography in terms of throughput while still maintaining superior resolution and higher degree of freedom in terms of printable geometries.
Highlights
Femtosecond laser based 3D nanolithography is a powerful tool for fabricating various functional microand nano-objects
With T denoting objective/system transmission coefficient, M2 being M-factor or deviation of the real beam from the perfect Gaussian beam and w0 = 0.61λ/numerical apertures (NA) (NA = n θ is the numerical aperture of an objective lens defined by the cone angle θ of the focusing optics and the refractive index n of the material)
While more complex electrical field distributions are present at focal point when focusing with objectives having NA > 0.248, Gaussian-based calculations yield the result which differs from the real voxel sizes less than 10%, which is completely acceptable for approximate calculations
Summary
Femtosecond laser based 3D nanolithography is a powerful tool for fabricating various functional microand nano-objects. It is shown that by varying objective numerical apertures (NA) from 1.4 NA to 0.45 NA, voxel size can be tuned in the range from sub μm to tens of mm, resulting in structuring rates between 1809 μm3/s and 313312 μm3/s at 1 cm/s translation velocity achieved via simultaneous movement of linear stages and scanners. It is mandatory to provide an adequate functionality and a reasonable price of the manufactured structures This dictates that the fabrication processes have to be extremely precise, flexible and, at the same time, sustain the high throughput. In this work on-demand control of feature size and optimization of throughput are presented It is achieved by employing objectives with different NA in conjunction with linear stage and galvo-scanner synchronization. An extensive discussion is provided, highlighting the advantages of chosen fabrication strategies and overall 3DLL position in relation to other common optical 3D printing techniques
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