3D printing by two-photon polymerization enables the fabrication of microstructures with complex shapes and critical dimensions of a few hundreds of nanometers. On state-of-the art commercial two-photon polymerization systems, an immense 3D design freedom can be put into practice by direct laser writing using a precise fabrication technology, which makes this approach highly attractive for different applications on the microscale, such as microrobotics, micro-optics, or biosensing. However, navigating the different possible configurations and selecting the optimal parameters for the fabrication process often requires intensive testing and optimization. In addition to the more established acrylate-based resins, there is a growing interest in the use of soft materials. In this paper, we demonstrate the fabrication of various microscale structures by two-photon polymerization using a Nanoscribe Photonic Professional GT+ commercial system. Furthermore, we describe the different configurations of the system and parameter selection, as well as commercial resins and their chemical and mechanical properties. Finally, we provide a short guide aiming to serve as starting point for the two-photon polymerization-based fabrication of various microscale architectures with distinct characteristics.

Microswimmers are a rapidly developing research area attracting enormous attention because of their many potential applications with high societal value. A particularly promising target for cleverly engineered microswimmers is the field of biomedical applications, where many interesting examples have already been reported for e.g., cargo transport and drug delivery, artificial insemination, sensing, indirect manipulation of cells and other microscopic objects, imaging, and microsurgery. Pioneered only two decades ago, research studies on the use of microswimmers in biomedical applications are currently progressing at an incredibly fast pace. Given the recent nature of the research, there are currently no clinically approved microswimmer uses, and it is likely that several years will yet pass before any clinical uses can become a reality. Nevertheless, current research is laying the foundation for clinical translation, as more and more studies explore various strategies for developing biocompatible and biodegradable microswimmers fueled by in vivo-friendly means. The aim of this review is to provide a summary of the reported biomedical applications of microswimmers, with focus on the most recent advances. Finally, the main considerations and challenges for clinical translation and commercialization are discussed.

Worldwide research in microrobotics has exploded in the past two decades, leading to the development of microrobots propelled in various manners. Despite significant advances in the field and successful demonstration of a wide range of applications, microrobots have yet to become the preferred choice outside a laboratory environment. After introducing available microrobotic propulsion and control mechanisms, microrobots that are manufactured and powered by light are focused herein. Referring to pioneering works and recent interesting examples, light is presented not only as a fabrication tool, by means of two‐photon polymerization direct laser writing, but also as an actuator for microrobots in both hard and soft stimuli–responsive polymers. In this scenario, a number of challenges that yet prevent polymeric light‐powered microrobots from reaching their full potential are identified, whereas potential solutions to overcome said challenges are suggested. As an outlook, a number of real‐world applications that light‐powered microrobots should be particularly suited for are mentioned, together with the advances needed for them to achieve such purposes. An interdisciplinary approach combining materials science, microfabrication, photonics, and data science should be conducive to the next generation of microrobots and will ultimately foster the translation of microrobotic applications into the real world.

A microfluidic chip for generation of gradients of dissolved oxygen was designed, fabricated and tested. The novel way of active oxygen depletion through a gas permeable membrane was applied. Numerical simulations for generation of O₂ gradients were correlated with measured oxygen concentrations. The developed microsystem was used to study growth patterns of the bacterium Pseudomonas aeruginosa in medium with different oxygen concentrations. The results showed that attachment of Pseudomonas aeruginosa to the substrate changed with oxygen concentration. This demonstrates that the device can be used for studies requiring controlled oxygen levels and for future studies of microaerobic and anaerobic conditions.

Fresnel reflection at the boundary between two media of differing refractive indices is a major contributing factor to the overall loss in mid-infrared optical systems based on high-index materials such as chalcogenide glasses. In this paper, we present a study of broadband antireflective moth-eye structures directly nanoimprinted on the surfaces of arsenic triselenide (${\mathrm{As}}_2{\mathrm{Se}}_3$)-based optical windows. Using rigorous coupled-wave analysis, we identify a relief design optimized for high transmittance ($<1\%$ reflectance) at 6 μm, which when nanoimprinted features a transmittance improvement ($\mathrm{\Delta }T>12\%$) in the 5.9–7.3 μm spectral range as well as improved omnidirectional properties. Finally, we demonstrate the adaptability of nanoimprinted surface reliefs by tailoring the nanostructure pitch and height, achieving both extremely broadband antireflective and highly efficient antireflective surface reliefs. The results and methods presented herein provide an efficient and scalable solution for improving the transmission of bulk optics, waveguides, and photonic devices in the mid-infrared.

Planar silicon chips with 1-2-μm etched holes (average resistance: 2.04 ± 0.02 MΩ in physiological buffer, n = 274) have been developed for patch-clamp recordings of whole-cell currents from cells in suspension. An automated 16-channel parallel screening system, QPatch 16, has been developed using this technology. A single-channel prototype of the QPatch system was used for validation of the patch-clamp chip technology. We present here data on the quality of patch-clamp recordings and from actual drug screening studies of human potassium channels expressed in cultured cell lines. Using Chinese hamster ovary (CHO) and human embryonic kidney cells (HEK), gigaseals of 4.1 ± 0.4 GΩ (n = 146) and high-quality whole-cell current recordings were obtained from hERG and KCNQ4 potassium channels. Success rates for gigaseal recordings varied from 40 to 95%, and 67% of the whole-cell configurations lasted for >20 min. Cells were maintained in suspension up to 4 h in a cell storage facility that is integrated in the QPatch 16. No decline in patchability was observed during this time course. A series of screens was conducted with known inhibitors of the hERG and KCNQ4 potassium channels. Dose-response relationship characterizations of verapamil and rBeKm-1 blockage of hERG currents provided IC₅₀ values similar to values reported in the literature.