POSTECH researchers achieve 2x stronger metal-polymer bonds using LPBF surface roughness control

Researchers at Pohang University of Science and Technology (POSTECH), led by Professor Kim Hyung-seop from the Department of Eco-Friendly Materials Science and Engineering, have developed a method to dramatically improve metal-polymer adhesion by precisely controlling surface roughness during laser powder bed fusion (LPBF) of Ti-6Al-4V. By adjusting laser power, scan speed, and hatch spacing, the team achieved roughness values from 20 to 70 µm and demonstrated spatial tailoring of roughness within a single part. In tests with silicone elastomers EcoFlex, Dragon Skin, and PDMS, adhesion strength improved by 214%, 229%, and up to 717 kPa respectively - more than double that of smooth surfaces. The work was published in Virtual and Physical Prototyping and supported by Korea's National Research Foundation, the Defense Acquisition Program Administration, and the Ministry of Trade, Industry and Energy.

This research addresses a persistent bottleneck in multi-material hybrid manufacturing: the weak interface between stiff metal structures and flexible polymers. Traditional solutions rely on chemical primers, adhesives, or mechanical fasteners that add cost, weight, and process complexity. POSTECH's approach exploits the inherent surface texture of LPBF - typically viewed as a defect requiring post-processing - and turns it into a functional interlocking mechanism analogous to hook-and-loop fasteners. The ability to spatially vary roughness opens the door to graded interfaces in soft robotics, implantable medical devices, and aerospace structures where rigid frames must transition to compliant skins. The work fits the IP lock-in grind pattern: the innovation is embedded in the LPBF process parameters themselves, creating a potential moat if integrated into certified workflows for medical or defense applications.

From an industry perspective, this is a process-level materials innovation rather than a product launch, so near-term commercial impact depends on adoption by LPBF system vendors or service bureaus. The key execution question is whether the roughness control can be implemented as a software-defined parameter set on existing LPBF platforms - such as those from EOS, SLM Solutions, or Nikon SLM - without hardware modifications. For end users in soft robotics or medical device manufacturing, the practical takeaway is that multi-material parts may soon be printable in a single LPBF run followed by polymer casting, eliminating secondary bonding steps. The research is solid but remains at lab scale; watch for follow-on work demonstrating fatigue performance and biocompatibility under cyclic loading.