Topographical characteristics of 3D printed polymeric microneedle surface and its impact on coating formulation attributes

In recent years, 3D printing has emerged as a promising technique for fabricating polymeric microneedles (μNDs), offering flexibility and precision. However, the surface topography of these μNDs plays a pivotal role in determining coating formulation characteristics and, consequently, their efficacy in drug delivery applications. This review delves into contemporary approaches for evaluating the surface topography of 3D printed polymeric μNDs, exploring its impact on coating formulation characteristics. With reference to the latest research in the materials industry, we elucidate the close relationship between the adhesion of coating material and μND surface, considering their physical and chemical properties. Fundamental principles relevant to understanding the influence of surface topography on therapeutic coating are discussed, emphasising how surface microtopography influences adhesion strength. Moreover, non-contact methodologies such as profilometry are reviewed for characterising μND surface morphology, highlighting their utility in assessing surface roughness, porosity, and feature geometry. Additionally, we explore how coating formulation attributes dictate surface wetting, surface energy, and interfacial adhesion strength. Insights from this review offer valuable guidance for optimising the fabrication process of 3D printed polymeric μNDs, tailoring their surface topography to enhance coating formulation performance in diverse biomedical applications.