Two‐Photon Laser Writing of Soft Responsive Polymers via Temperature‐Controlled Polymerization

Abstract

Enhancing the resolution of 3D patterning techniques in functional soft polymers enlarges the application areas of responsive shape‐changing materials, for tunable nanophotonics and nanorobotics. Thanks to the recent advances of polymer science, the palette of available materials for nanomanufacturing is becoming wider and wider—although the comprehension of their polymerization process by two‐photon polymerization is still incomplete. In this work, both shrinking of the minimal polymerizable unit and a significant improvement of the mechanical stability of microstructured soft polymers, in particular of liquid crystalline networks, are demonstrated. To this aim, temperature control enhances the resolution and reduces the swelling of the polymerized structures, thus avoiding deviations of the final structure from the intended design. This fine control on the nanoscale features enables the use of soft responsive materials not only for bulky microelements, but also for high‐resolution structures with more complex design.

Chiral Metasurfaces with Maximum Circular Dichroism Enabled by Out‐of‐Plane Plasmonic System

“…Additionally, there exists minor reflection asymmetries between the crosspolarization reflection magnitudes r LR and r RL which might result from the fabricated chiral metasurfaces without any rotational symmetry due to fabrication errors and accumulated measurement errors, resulting in the all elements in the Jones matrix are different. [57] Due to the scaling properties of Maxwell's equations and 3D printing techniques, therefore, this paradigm can be easily extended to other frequency ranges(Figure S10, Supporting Information) and fabricated by integrating various 3D printing techniques with appropriate printing resolution and printing scale, such as micro/nano scale two-photon polymerization (TPP) based 3D printing techniques [58][59][60] for optical metasurfaces, millimeter-scale projection stereolithography-based 3D printing techniques [61] and fused deposition modeling (FDM) printing techniques [62] for microwave metasurfaces. Such strong chiroptical responses together with the concise and general design principle, and the simple, scalable, low-cost, and lithographyfree fabrication strategy, hold promising potential in various chirality-related applications, such as chiral sensing, imaging, spectroscopy, and polarimetry.…”

Temperature Tunable 4D Polymeric Photonic Crystals

“…One major hurdle in the fabrication of soft photonic structures is the reproducibility of the results and the fidelity of the final structure with respect to the intended design, which was here overcome by the temperature‐controlled TP‐DLW [ 42 ] also leading to a more spheroidal shape of the voxel. Figure 3b,c shows two PCs printed at room temperature and 10 °C, respectively.…”

“…As expected, the treatment [ 46 ] determines a slight blueshift due to the overall reduction of the rod minor and major axis. [ 42 ] Moreover, thanks to the swelling decrease, the periodicity of the structure is improved (see Figure 2d–f), therefore producing a larger attenuation (10% reduction) of the woodpile transmission at the stop band. One major difference in the 3D printing of soft materials at different temperatures is the reproducibility of the process.…”

“…The authors have already shown that a polymerization temperature of 10 °C slows down the monomer diffusion in soft responsive materials, improving the resolution and the mechanical stability up to performances typical of commercial glassy resists. [ 42 ] Furthermore, lowering the polymerization temperature makes the polymerizable unit (the voxel) more spheroidal thus reducing the aspect ratio (i.e., the ratio among the major and minor axis of the voxel) and, last but not least, greatly improves the reproducibility of the printed structures, thus opening to the fabrication of photonic crystals able to work in dry environment.…”

In Situ Diagnostics and Role of Light‐Induced Forces in Metal Laser Nanoprinting

“…Multi‐photon 3D laser micro‐ and nanoprinting of polymers [ 1,2 ] has become a commercially available and routine research tool in optics, [ 3–5 ] mechanics, [ 6–8 ] biology, [ 9,10 ] and micro‐robotics, [ 11–15 ] and is starting to enter the industrial market. Even multi‐material multi‐photon 3D printing is emerging.…”