The direct laser writing technique based on two-photon polymerization (TPP) has evolved considerably over the past two decades. Its remarkable characteristics, such as 3D capability, sub-diffraction resolution, material flexibility, and gentle processing conditions, have made it suitable for several applications in photonics and biosciences. In this review, we present an overview of the progress of TPP towards the fabrication of functionalized microstructures, whispering gallery mode (WGM) microresonators, and microenvironments for culturing microorganisms. We also describe the key physical-chemical fundamentals underlying the technique, the typical experimental setups, and the different materials employed for TPP.
The capability of modifying and patterning the surface of polymer and composite materials is of high significance for various biomedical and electronics applications. For example, the use of femtosecond (fs) laser ablation for micropatterning electrospun nanofiber scaffolds can be successfully employed to fabricate complex polymeric biomedical devices, including scaffolds. Here we investigated fs-laser ablation as a flexible and convenient method for micropatterning polyamide (PA6) electrospun nanofibers that were modified with molybdenum disulfide (MoS2). We studied the influence of the laser pulse energy and scanning speed on the topography of electrospun composite nanofibers, as well as the irradiated areas via scanning electron microscopy and spectroscopic techniques. The results showed that using the optimal fs-laser parameters, micropores were formed on the electrospun nanofibrous membranes with size scale control, while the nature of the nanofibers was preserved. MoS2-modified PA6 nanofibrous membranes showed good photoluminescence properties, even after fs-laser microstructuring. The results presented here demonstrated potential application in optoelectronic devices. In addition, the application of this technique has a great deal of potential in the biomedical field, such as in tissue engineering.
Fabrication
of functional silk fibroin microstructures has extensive
applications in biotechnology and photonics. Considerable progress
has been made based on lithographic methods and self-assembly approaches.
However, most methods require chemical modification of silk fibroin,
which restricts the functionalities of the designed materials. At
the same time, femtosecond laser-induced forward transfer (fs-LIFT)
has been explored as a simple and attractive processing tool for microprinting
of high-resolution structures. In this paper, we propose the use of
LIFT with fs-pulses for creating high-resolution structures of regenerated
silk fibroin (SF). Furthermore, upon adding Eu3+/Tb3+ complexes to SF, we have been able to demonstrate the printing
by LIFT of luminescent SF structures with a resolution on the order
of 2 μm and without material degradation. This approach provides
a facile method for printing well-defined two-dimensional (2D) micropatterns
of pure and functionalized SF, which can be used in a wide range of
optical and biomedical applications.
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