Molding three-dimensional azopolymer microstructures with holographically structured light

Structured surfaces offer attractive functionalities that are inaccessible to their planar counterparts. To improve performance and expand their range of applications, fabrication methods for artificial microstructured surfaces aim to create complex and diverse shapes, along with the ability to locally structure either singular or collective microstructures. Standard lithography techniques typically do not allow for the simultaneous achievement of morphological complexity, geometrical diversity, and localized control, while exhibiting fast and scalable patterning for large areas. Azobenzene-containing materials can offer a straightforward and cost-effective solution for creating three-dimensional microstructures by reshaping flat or pre-patterned surfaces using light. However, typical illumination schemes still have limitations in terms of geometrical diversity and localized structuring, similar to conventional methods. In this work, we use computer generated holography to digitally control light intensity gradients for locally driving reconfiguration of micropillars in three dimensions. We demonstrate the fabrication of microstructures with diverse morphologies, including concave, convex, asymmetric, multi-slanted faceted, and complex profiles. Moreover, we demonstrate the ability to reshape groups of microstructures in a one-step process, where each element in the field of view of the hologram is controlled with an individualized morphology. Our approach can open new routes for the fabrication of complex microstructures through a maskless, straightforward, and cost-effective method that uses only light to reshape surfaces with on-demand geometry and functionality.