Growth and characterization of ZnO nanostructures on 3D-printed thermoplastic polymers for biosensing and biomedical applications

Recently, 3D-printed materials have been used in many applications, from mechanical parts to electronic and biomedical devices. However, these thermoplastic polymers often have limitations in surface chemistry, biocompatibility, and conductivity because they are thermal and electrical insulators. Here, four thermoplastic polymers, polylactic acid (PLA), polyethylene terephthalate glycol (PETG), acrylonitrile styrene acrylate (ASA), and thermoplastic polyurethane (TPU), were 3D-printed and coated with ZnO nanostructures using a low-temperature chemical-bath method. FE-SEM, EDS, FTIR, and XRD were used to characterize the morphology, elemental composition, chemical bonding, and crystal structure, respectively. The mean ZnO nanorod diameters were 178 nm for PLA, 193 nm for PETG, 164 nm for ASA, and 99 nm for TPU. The corresponding mean nanorod lengths were 1041, 1137, 1335, and 750 nm, respectively. Additional photoluminescence, impedance spectroscopy, bacterial activity, protein adsorption, and water-contact-angle measurements were conducted to evaluate the functional effects of the coating. Photoluminescence analysis revealed a near-band-edge feature near 380 nm, while electrical measurements showed improved surface conductivity after coating. No measurable inhibition zone is observed under the tested disk-diffusion conditions. Protein adsorption varied with the polymer substrate, and wettability depended on both the ZnO coating and the surface finish. These findings demonstrate that ZnO coating produces substrate-dependent structural, optical, electrical, and interfacial responses in 3D-printed polymers, which are expected to broaden their use in several applications including biosensing and biomedical devices.