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Light-responsive devices are becoming increasingly relevant in many applications ranging from soft-robotics, energy harvesting, regenerative medicine and tissue engineering. Here we present a two-photon fabrication process based on a photocurable azopolymeric compound that we successfully employed to manufacture suspended micro-membranes. Thanks to the incorporation of azobenzene units, the membranes are shown to exhibit a remarkable mechanical photo-responsivity despite the disordered, amorphous structure of the crosslinked network. When irradiated with a focused laser beam at 532 nm wavelength, a reversible shape modification is observed, with a linear expansion coefficient as large as 28%. This effect is accompanied by a refractive index decrease of about 0.16, as measured interferometrically. The initial state of the membrane is fully recovered when the irradiation is switched off, as the cyclic photoisomerization process is stopped. The presented approach can be extended to light-induce complex modifications of the mechanical features in 3D printed objects by remotely providing arbitrary illumination patterns.

Stable suspensions of spherical 10–15 nm superparamagnetic iron oxide nanoparticles (SPIONs) have been synthetized by co-precipitation, stabilized with citric acid, surface functionalized with aminopropyltriethoxysilane (APTES) and finally decorated with ultra-small gold nanoparticles (GNPs) by in situ reduction of a soluble gold salt (HAuCl 4 ), obtaining well dispersed SPIONs-GNPs colloids. The morphology, size and stability of the SPIONs-GNPs suspensions have been controlled by adjusting the molar ratio of the reagents (Fe/HAuCl 4 and Fe/APTES). The synthesis route differs from that typically found in literature, using tunable chelating layer modifications (such as citric acid and –NH 2 groups) of the magnetic core, depositing GNPs on the amine-functionalized iron oxide surface without the use of a specific reducing agent, and tuning the process pH and temperature. An explanation of how the different chemical species involved in the synthesis route could be responsible for the reducing action has been provided. The SPIONs-GNPs colloids have been characterized after each synthesis step by Transmission Electron Microscopy (TEM), Scanning Transmission Electron Microscopy (STEM), energy-dispersive X-ray spectroscopy (EDXS), Fourier transform infrared spectroscopy (FTIR), ζ Potential measurements, magnetic measurements with a vibrating-sample magnetometer (VSM) and UV–VIS spectroscopy. The SPIONs-GNPs colloids showed magnetoplasmonic behaviors since they maintained the plasmonic properties of GNPs and the superparamagnetic response of iron oxide NPs.

Cell–substrate interactions can modulate cellular behaviors in a variety of biological contexts, including development and disease. Light‐responsive materials have been recently proposed to engineer active substrates with programmable topographies directing cell adhesion, migration, and differentiation. However, current approaches are affected by either fabrication complexity, limitations in the extent of mechanical stimuli, lack of full spatio‐temporal control, or ease of use. Here, a platform exploiting light to plastically deform micropatterned polymeric substrates is presented. Topographic changes with remarkable relief depths in the micron range are induced in parallel, by illuminating the sample at once, without using raster scanners. In few tens of seconds, complex topographies are instructed on demand, with arbitrary spatial distributions over a wide range of spatial and temporal scales. Proof‐of‐concept data on breast cancer cells and normal kidney epithelial cells are presented. Both cell types adhere and proliferate on substrates without appreciable cell damage upon light‐induced substrate deformations. User‐provided mechanical stimulation aligns and guides cancer cells along the local deformation direction and constrains epithelial colony growth by biasing cell division orientation. This approach is easy to implement on general‐purpose optical microscopy systems and suitable for use in cell biology in a wide variety of applications.

In many optical applications, there is an increasing need for dynamically tunable optical elements that are able to shape the wavefront of light ‘on demand’. In this work, an elastomeric easy-to-fabricate optical element whose transmission functions can be reversibly phase configured by visible light is demonstrated. The light responsivity of proper azopolymers incorporated within an elastomeric matrix is exploited to induce a light-controlled graded refractive index (GRIN) distribution within the bulk compound. The induced refractive index distribution is continuous and conformal to the intensity profile of the illumination at moderate power. A 100 mW doubled-frequency Nd:YAG Gaussian beam focused to a 650 μm waist is shown to induce a maximum relative refractive index change of ~0.4% in the elastomeric matrix, with an approximately parabolic profile. The restoring characteristics of the elastomeric matrix enable full recovery of the initial homogeneous refractive index distribution within a few seconds when the incident laser is switched off. As an exemplary application, the configurable GRIN element is used in a microscope-based imaging system for light control of the effective focal length., Adaptive optics: bouncy solution to on-demand focusing By incorporating photosensitive molecules into a rubbery matrix, researchers have created a lens that can be dynamically re-shaped using visible light. Most tunable lenses rely on special lithographic patterns to manipulate light, but natural systems such as the human eye use variable refractive index changes for adjustable focus. Emiliano Descrovi at the Polytechnic University of Turin in Italy and colleagues have developed an optical element flexible enough to deliver refractive index gradients through laser beam writing. The team found that azopolymers — compounds that switch orientation and expand under light stimulus — could introduce predictable, parabolic refractive index changes of up to 0.4% inside a polydimethylsiloxane substrate after pinpoint irradiation. Imaging experiments demonstrated the possibility of resolving objects by manipulating laser exposure times to progressively increase the new lens’ focal length.

In recent years, the ability to pattern large areas at the micro- and nano-scale with stimuli-responsive materials has opened the opportunity to engineer surface structures and trigger peculiar properties such as complex optical functionalities or surface properties by laser-matter interactions. The use of light-sensitive materials, such as azobenzene compounds, can open the opportunity to active manipulate in terms of morphology, physical and mechanical properties a pre-patterned architectures, which are intrinsically static once fabricated. We employ azopolymers, in which the rapid and reversible photoisomerization reaction of azobenzene molecules can actuate mass transport phenomena typically parallel to the light polarization. The azopolymeric film is patterned by soft-imprinting as an array of micro-holes showing a well-defined isotropic round pores. Upon a linearly polarized illumination (365 nm, 150 W/cm2), we observe a deformation of the initial holes along the polarization direction, in such a way that the circular pores are transformed into long closed slits. A rotation of the polarization by 90° triggers a reconfiguration of the pristine round shape, with a good degree of control of the photo-induced pore reshaping. Due to the polarized-directionality of the photo-manipulation we demonstrate the possibility to tune the pristine morphology and properties along specific directions, providing a smart engineered platform with different reshaped micro-patterns. The light-induced contraction and expansion reshaping strategy of a porous polymeric structures shows exciting potential for a number of applications including microfluidics, lithography and tissue engineering. Tuning cells behavior in response to material manipulation cues is a promising goal in biology

In this work we investigate new degrees of freedom in controlling the physical properties of structured photo-sensitive materials that can be usefully exploited in many application fields. We employ azopolymers, a class of light responsive materials, which are structured in micro-pillar array. A reversible and controlled change in morphology of a pre-patterned polymeric film under properly polarized illumination is demonstrated to provide the opportunity to engineer surface structures and dynamically tune their properties. We exploit the laser process taking advantage of the light-induced deformation of a micro-textured azopolymeric film in order to modify the surface hydrophobicity along specific direction.

We propose a liquid polymeric compound based on photo-responsive azo-polymers to be used as light-activated optical element with tunable and reversible functionalities. The interaction of a laser beam locally modifies the liquid density thus producing a refractive index gradient. The laser induced refractive index profiles are observed along the optical axis of the microscope to evaluate the total phase shift induced and along the orthogonal direction to provide the axial distribution of the refractive index variation. The focusing and imaging properties of the liquid lenses as functions of the light intensity are illustrated.

Azopolymers are known to exhibit a strong light responsivity known as athermal photofluidization. Although the underlying physics is still under debate, athermal photofluidization has been demonstrated to trigger mass-migration according to the polarization of a proper illumination light. Here, a polymer blend is proposed wherein a commercial azo-polyelectrolyte is mixed with a passive polymer. The blend is patterned as an array of micro-pillars that are individually exposed to visible laser illumination. Thanks to the interplay between the two blend components, a reversible and controlled deformation of the micro-pillars by periodically tuning the laser polarization in time is demonstrated. A reduced mobility of the azo-compound allows to repeatibly elongate and rotate micro-pillars along specific directions, with no significant material flow outisde the initial volume and no significant degradation of the structure morphology over several cycles. The proposed work suggests new degrees of freedom in controlling the mechanical features of micro-patterned light-responsive materials that can be usefully exploited in many application fields.

We propose optically reconfigurable polymeric microstructures. Azopolymer-PMMA composite is pre-structured in micro-pillar array. The reversible shaping of photosensitive structures guided by the polarization state of the incident light is demonstrated.

The light-induced deformation of a micro-textured photo-sensitive polymeric material is exploited for modifying the surface hydrophobicity along deterministic directions. Arrays of azopolymeric micro-pillars are fabricated over large area and irradiated with a green laser. Upon laser irradiation, the micro-pillars deform reversibly along a direction parallel to the laser polarization, resulting in elongated shapes with controllable eccentricity. Such a locally anisotropic topography induces a directional yet reversible change of hydrophobicity, as measured by contact angles varying within a range of 30°.

Il saggio illustra alcuni passaggi delle trasformazioni urbane di Roma Capitale rispetto alla realizzazione del quartiere operaio di Testaccio. Dopo il 20 settembre del 1870, in relazione ai programmi di sviluppo della città, Testaccio viene destinato a zona industriale della Capitale; in base a tale destinazione verrà deciso di realizzare in quella zona il nuovo Mattatoio di Roma. Con la costruzione del Mattatoio, progettato da Gioacchino Ersoch (1888-1891), il quartiere registrerà un progressivo incremento demografico che farà di Testaccio, agli inizi del Novecento, una delle zone più degradate di Roma. In questi anni, però, grazie alla Giunta comunale guidata da Ernesto Nathan (10 novembre 1907- dicembre 1913) e all’infaticabile attività di Domenico Orano – studioso, filantropo e, dal 1910, consigliere comunale (eletto nelle file del blocco popolare) –, verranno promossi numerosi istituti di assistenza economica, educativa, ricreativa e sanitaria che porteranno a trasformare Testaccio da malfamato ghetto-dormitorio ad autonomo e riconoscibile quartiere della città.