Mesoscale 3D manufacturing: varying focusing conditions for efficient direct laser writing of polymers

Abstract

In this paper, we report a novel approach for efficient fabrication of mesoscale polymer 3D microstructures. It is implemented by direct laser writing varying exposure beam focusing conditions. By carefully optimizing the fabrication parameters (laser intensity, scanning velocity/exposure time, changing objective lens) complex 3D geometries of the microstructures can be obtained rapidly. Additionally, we demonstrate this without the use of the photoinitiator as photosensitizer doped in the pre-polymer material (SZ2080). At femtosecond pulsed irradiation ∼TW/cm 2 intensities the localized free radical polymerization is achieved via avalanche induced bond braking. Such microstructures have unique biocompatibility and optical transparency as well as optical damage threshold value. By creating the bulk part of the structure using low-NA (0.45) objective and subsequently fabricating the fine features using oil immersion high-NA (1.4) objective the manufacturing time is reduced dramatically (30 x is demonstrated). Using this two objective method a prototype of functional microdevice was produced: 80 and 85 µm diameter microfluidic tubes with the fine filter consisting of 4 µm period grating structure that has 400 nm wide threads, which corresponds to a feature precision aspect ratio of ∼200. Therefore, such method has great potential as a polymer fabrication tool for mesoscale optical, photonic and biomedical applications as well as highly integrated 3D µ-systems. Furthermore, the proposed approach is not limited to lithography and can be implemented in a more general type of laser writing, such as inscription within transparent materials or substractive manufacturing by ablation.

Effect of micron-scale manufacturing flaws on the tensile response of centimeter sized two-photon polymerization microlattices

“…interdigitated sub-lattices). [26] The refractive index of acrylate systems is known to vary as function of the degree of cure, [27] and the degree of conversion is also well known to increase with greater dosage. [23] Thus, structures fabricated with higher peak laser intensities will exhibit greater refractive index changes enhancing the likely hood of distortions.…”

Multiresolution layered manufacturing

“…The idea of using several different manufacturing technologies to shorten fabrication times is also hardly new; there is a large body of previous work on hybrid manufacturing technologies (Chu et al , 2014; Zhu et al , 2013). Focusing on the combination of different technologies for high-resolution layered manufacturing, there have been efforts to do additive/additive combinations, such as UV stereolithography and TPP (Eschenbaum et al , 2013), additive and subtractive TPP (Lim et al , 2011; Xiong et al , 2012), FFF (fused filament fabrication) and subtractive direct laser writing (Malinauskas et al , 2014), FFF and TPP (Balčiunas et al , 2014) and TPP at several different resolutions (Jonušauskas and Malinauskas, 2014; Lim et al , 2006).…”

Employment of fluorescence for autofocusing in direct laser writing micro-/nano-lithography

“…Scaling as well as increase of fabrication throughput was and remains a serious issue since the emergence of the technique. [57][58][59][60][61] Nevertheless, several important issues have to be solved prior to fully transferring the technology from a scientific laboratory to a manufacturing line in a factory. Basically, structure's height is no longer limited as it can be obviated by dip-in 62 or WOW 63 approaches.…”