Topography of material surfaces is known to influence cell behavior at different levels: from adhesion up to differentiation. Different micro- and nanopatterning techniques have been employed to create patterned surfaces to investigate various aspects of cell behavior, most notably cellular mechanotransduction. Nevertheless, conventional techniques, once implemented on a specific substrate, fail in allowing dynamic changes of the topographic features. Here we investigated the response of NIH-3T3 cells to reversible topographic signals encoded on light-responsive azopolymer films. Switchable patterns were fabricated by means of a well-established holographic setup. Surface relief gratings were realized with Lloyd's mirror system and erased with circularly polarized or incoherent light. Cell cytoskeleton organization and focal adhesion assembly proved to be very sensitive to the underlying topographic signal. Thereafter, pattern reversibility was tested in air and wet environment by using temperature or light as a trigger. Additionally, pattern modification was dynamically performed on substrates with living cells. This study paves the way toward an in situ and real-time investigation of the material-cytoskeleton crosstalk caused by the intrinsic properties of azopolymers.

Lab-on-a-Chip (LoC) devices are extremely promising in that they enable diagnostic functions at the point-of-care. Within this scope, an important goal is to design imaging schemes that can be used out of the laboratory. In this paper, we introduce and test a pocket holographic slide that allows digital holography microscopy to be performed without an interferometer setup. Instead, a commercial off-the-shelf plastic chip is engineered and functionalized with this aim. The microfluidic chip is endowed with micro-optics, that is, a diffraction grating and polymeric lenses, to build an interferometer directly on the chip, avoiding the need for a reference arm and external bulky optical components. Thanks to the single-beam scheme, the system is completely integrated and robust against vibrations, sharing the useful features of any common path interferometer. Hence, it becomes possible to bring holographic functionalities out of the lab, moving complexity from the external optical apparatus to the chip itself. Label-free imaging and quantitative phase contrast mapping of live samples are demonstrated, along with flexible refocusing capabilities. Thus, a liquid volume can be analyzed in one single shot with no need for mechanical scanning systems.

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The dynamic instability of the moving vortex lattice at high driving currents in NbN/CuNi-based and NbN nanostripes designed for optical detection has been studied. By applying the model proposed by Larkin and Ovchinnikov [Zh. Eksp. Teor. Fiz. 68, 1915 (1975)], from the critical velocity v ∗ for the occurrence of the instability, it was possible to estimate the values of the quasiparticle relaxation times τE. The results show that the NbN/CuNi-based devices are characterized by shorter values of τE compared to that of NbN