High-aspect 3D two-photon polymerization structuring with widened objective working range (WOW-2PP)

Abstract

We developed a novel two-photon polymerization (2PP) configuration for fabrication of high-aspect three-dimensional (3D) structures, with an overall height larger than working distance of the microscope objective used for laser beam focusing into a photosensitive material. This method is based on a modified optical 2PP setup, where a microscope objective (1003 high N.A.), immersion oil and cover glass can be moved together into the photosensitive material, resulting in an effective higher and wider objective working range (WOW-2PP). The proposed technique enables the fabrication of high-aspect structures with sub-micrometer process resolution. 3D structures with a height of 7 mm are demonstrated, which could hardly be built with the conventional 2PP set-up due to refractive index mismatch and laser beam disturbances.

Micro additive manufacturing using ultra short laser pulses

“…at an angle to the axis of the structuring beam. Here, the change in refractive index induced to the photosensitive material by the polymerization process enables visualization of the polymerized structure [82]. Measuring this change in refractive index by interferometry was also proven feasible to be used for insitu monitoring of the polymer conversion [110].…”

“…3D structures with a height of 7 mm are demonstrated (see Fig. 20), which could hardly be built with the conventional 2PP set-up due to refractive index mismatch and laser beam disturbances [82]. The two-photon polymerization process consists of several physical phenomena such as generation and propagation of spatial and temporal intensity distribution, nonlinear two-photon absorption, bulk heating, reaction kinetics during polymerization and material dependent post-processing.…”

“…(b) Configuration of WOW-2PP with 100Â high-magnification microscope objective. (c) Configuration of 10Â low-magnification microscope objective[82].Fig. 20.…”

Microfabrication Processes and Applications of Liquid Photosensitive Materials

“…mm-nm scales), they are excellent candidates to be applied for the fabrication of three-dimensional (3D) microsized objects with high precision. 2,4 For instance, as demonstrated in Figure 6.5, using a laser with a wavelength of 780 nm and a pulse width of less than 140 fs, the fabrication of high aspect ratio (HAR) 3D microstructures such as a grid tower (grid width B771 nm and tower height B459 mm) and Tokyo Skytree (feature width B1.2 mm and height B293 nm) were made of photosensitive material by Obata et al 25 This recent work of microfabrication demonstrated here is promising for future applications. In addition, more various micro-to nanoscale technologies related with photosensitive materials have been currently explored and developed.…”

Synthesis of new photoactive urethane carbohydrates and their behavior in UV or femtosecond laser-induced two-photon polymerization

“…Inducing a two-photon absorption by femtosecond (fs) laser pulses, the polymerization within the volume of the resin with the formation of 3D structures occurs, the process being thus labeled as the two-photon polymerization (2PP). [32,33] In fact, the 2PP represents a rapid prototyping technology and according to Waterman et al, this type of technology may reduce the time to market by 90% and costs by up to 70%. [34] Owing to the versatility of the process, the 2PP technique was useful in the fields of photonics, [35] microfluidics, [36] and biological tissue engineering.…”