Fabrication and characterisation of Ti and DLC coatings on metamaterial-architecture-inspired 3D-printed polymer substrates

Abstract

This research explores the fabrication and characterisation of metamaterial-architecture-inspired 3D-printed polymer substrates with complex geometries, subsequently functionalized with titanium (Ti) and diamond-like carbon (DLC) coatings deposited by direct current magnetron sputtering. In this context, the term <i>metamaterial-architecture-inspired</i> refers exclusively to the engineered surface geometry and does not imply the experimental demonstration of emergent metamaterial properties. Polymeric substrates were fabricated via laser stereolithography using both an industrial (SLA-3500) and a low-cost (Form 1+) printing system, employing photoreactive resins in a layer-by-layer process. Ti and DLC thin films were subsequently deposited, and the resulting surfaces were characterised using reflected light optical microscopy and Raman spectroscopy to assess geometrical fidelity, coating conformity, and chemical-structural stability. Uniform coatings were successfully achieved on complex three-dimensional microtextures using both SLA systems. Substrates printed with the SLA-3500 exhibited well-defined layers and an average increase in valley curvature of approximately 2.8%, whereas Form 1 + printed samples showed a higher deviation of about 17.7% relative to the original design. Raman spectroscopy confirmed the presence of characteristic D and G bands at 1396 cm⁻¹ and 1589 cm⁻¹ in DLC-coated samples on both Accura^®60 and Clear FLGPCL 02 substrates, indicating graphitic carbon domains while preserving the chemical integrity of the underlying polymer. Ti-coated surfaces exhibited increased broadband intensity between 1200 and 1420 cm⁻¹, attributed to resin-metal interactions. Despite minor variations in spectral intensity, no significant shifts in vibrational frequencies were observed, demonstrating comparable molecular stability of both substrate systems following coating deposition. These results establish a reliable framework for the fabrication and surface functionalization of architected polymer substrates, enabling future investigations into structure-property relationships and application-specific functional performance.