Nano-Second Laser Interference Photoembossed Microstructures for Enhanced Cell Alignment

Photoembossing is a powerful photolithographic technique to prepare surface relief structures relying on polymerization-induced diffusion in a solventless development step. Conveniently, surface patterns are formed by two or more interfering laser beams without the need for a lithographic mask. The use of nanosecond pulsed light-based interference lithography strengthens the pattern resolution through the absence of vibrational line pattern distortions. Typically, a conventional photoembossing protocol consists of an exposure step at room temperature that is followed by a thermal development step at high temperature. In this work, we explore the possibility to perform the pulsed holographic exposure directly at the development temperature. The surface relief structures generated using this modified photoembossing protocol are compared with those generated using the conventional one. Importantly, the enhancement of surface relief height has been observed by exposing the samples directly at the development temperature, reaching approximately double relief heights when compared to samples obtained using the conventional protocol. Advantageously, the light dose needed to reach the optimum height and the amount of photoinitiator can be substantially reduced in this modified protocol, demonstrating it to be a more efficient process for surface relief generation in photopolymers. Kidney epithelial cell alignment studies on substrates with relief-height optimized structures generated using the two described protocols demonstrate improved cell alignment in samples generated with exposure directly at the development temperature, highlighting the relevance of the height enhancement reached by this method. Although cell alignment is well-known to be enhanced by increasing the relief height of the polymeric grating, our work demonstrates nano-second laser interference photoembossing as a powerful tool to easily prepare polymeric gratings with tunable topography in the range of interest for fundamental cell alignment studies.

Topographic and geomorphological features of a hydrothermal field in submarine Mienhua Volcano offshore northeastern Taiwan

<p>There is a high potential of hydrothermal mineral deposits in the Southern Okinawa Trough offshore northeastern Taiwan. This study aims to integrate bathymetry data, water column images, seabed image, sub-bottom profiles and ROV observations to better understand a hydrothermal field, submarine Mienhua Volcano (MHV). A repeated mapping survey equipped with EM-712 was conducted to see if significant bathymetric changes took place since 50 days in MHV. The volcano of 2 km width and 240-m relief height is present at about 1300-m water depth near Mienhua Canyon. The volcano combines with several small and rugged mounds. From ROV observations, two of the mounds show active hydrothermal vents covered by white tubeworms and a white smoker with some mussels, respectively. In addition, active water column gas flares are observed on the southeastern part of MHV. Based on the identification of sub-bottom profiles, the special distribution of acoustic blanking zone shows the southeastern part is more narrow than the northwestern area. However, comparing the bathymetry mapped in two times, no obvious overall morphological changes are detected, except on the volcano rim. Seabed image also reveals similar backscatter intensity within the rugged mounds, suggested they may be at similar stages of morphological development. We consider that the hydrothermal vents are variable. In addition, the preliminary results indicate the fluid migration is the important process to influence the evolution of the hydrothermal field in MHV. Therefore, we also applied more seafloor images, geochemical and geophysical data which have been reported in MHV. Our results could evaluate the relationship between the flare activities, geomorphological features and the location of the blanking zone in the sedimentary strata.</p>

Investigation of the influence of amplitude spiral zone plate parameters on produced energy backflow

Investigation of the influence of parameters of silver, aluminum, gold, and chromium spiral zone plates on the longitudinal component of Umov-Pointing vector in produced optical vortices by using the frequency-dependent finite-difference time-domain method is presented. It is shown that the aluminum spiral zone plate with a relief height of 50 nm gives an optical vortex with the smallest longitudinal component of Umov-Pointing vector on the optical axis. The gold spiral zone plate is the least effective for the formation of vortex beams with a reverse energy flow.