Development of Uniform and Hierarchical Nanostructures on 2D and 3D Polymeric Surfaces: A Colloidal Lithography Approach

• Nanostructures are useful for biomedical, photovoltaics, and energy storage fields. • Hierarchical nanostructures boost bactericidal efficacy and antireflective traits. • They also improve light extraction and performance in photonic devices. • Current fabrication methods are complex and limited to 2D surfaces. • The method creates hierarchical nanostructures on both 2D and 3D polymer surfaces. Nanostructured surface (NSS) modifications have evolved over the last decade by mimicking natural surfaces, such as cicada and dragonfly wings. These modifications find applications in biomedical, photovoltaics, and energy storage. Despite advances in additive manufacturing, the development of polymeric NSS modifications remains limited. Current fabrication methods are complex, lack hierarchical architecture, and are generally restricted to two-dimensional (2D) substrates. Interestingly, hierarchical structures offer significant benefits for applications requiring high bactericidal efficacy (BE), omnidirectional anti-reflective properties, improved light extraction in light-emitting diodes (LEDs), and enhanced performance in optical, optoelectronic, and electrooptical devices. In this article, we introduce a facile technique for producing uniform-periodic (UP), multi-periodic hierarchical (MPH), and random hierarchical (RH) nanostructures on both 2D and three-dimensional (3D) surfaces via moulded flat (MF), 3D printed flat (3DPF) and 3D printed curve (3DPC) polylactic acid (PLA) forms. We employed a modified Langmuir-Blodgett (LB) technique to coat polystyrene (PS) microspheres in a monolayer, serving as a mask for Colloidal Lithography (CL). Modified surfaces were characterised via Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Drop Shape Analyser, and Fourier Transform Infrared Spectroscopy (FTIR). Using 520 nm microspheres, UP nanocones were produced, whereas 290 nm microspheres yielded UP nanowires. A 1:1 combination of both sizes resulted in MPH nanostructures on 2D surfaces and RH nanowires on 3D printed surfaces. These nanowires mimic dragonfly wing architecture, may be effective for applications with complex 3D-geometries, such as patient-specific implants, photovoltaics, optical, absorbents, sensors, microfluidics, and energy harvesting devices, although further validation is required.