Light doesn't just illuminate: it can become a true instrument capable of setting a material in motion. This is the prospect opened by the study 'Photo-guided Azopolymer Hydrogel Actuators', published in the journal 'Light: Science & Applications', whose authors include Emiliano Descrovi from the Department of Applied Science and Technology (Disat), who coordinated the work, and David Urban, who completed a joint doctoral programme between the Norwegian University of Science and Technology (NTNU) and the Polytechnic University of Turin.
At the heart of the research is a photoresponsive hydrogel — a soft, water-rich polymeric material capable of responding to light, with characteristics similar to those of biological tissues. Incorporated within it are azopolymer nanoparticles: tiny light-sensitive 'motors' that, when illuminated, change shape following the direction of polarisation of the light beam. This hydrogel captures and transmits this movement to the entire structure, giving it elasticity, stability even in aqueous environments, and the reversibility of mechanical actuation.
The possible applications are of interest above all in the biomedical sector. The material has been designed as a dynamic substrate for cell growth: by locally modifying its shape using light, it will be possible to guide the orientation, migration and compartmentalisation of cells and tissues, with a level of spatial and temporal control unachievable with traditional static substrates. All of this can be implemented using a conventional laboratory microscope. The platform could also be used in the development of microfluidic devices, systems for the three-dimensional culture of cells and organoids, optical microvalves and light-controlled intelligent microsystems, opening new prospects for regenerative medicine, drug delivery and biotechnology.
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