"Porous Anchor" That Strongly Bonds Dissimilar Materials Formed Simply by Coating and Drying

Multi-material structures are becoming increasingly important for developing lightweight vehicles, flexible electronics, and soft robots. These structures combine hard materials (metals, glass, ceramics) with soft polymers (rubber, plastics).
However, materials with different properties are difficult to bond together, and conventionally, an adhesive compatible with each material combination needed to be designed and developed (Figure (a), bottom left). While it is also known that bonding strength can be enhanced by roughening the surface of a substrate via mechanical scratching or chemical etching (Figure (a), bottom right), this method has problems from the perspectives of energy consumption and environmental considerations, including the increased complexity of the manufacturing process and the generation of residues during processing.

In this study, the research team has developed a new method of joining dissimilar materials by structuring the adhesive layer. The team used a physical phenomenon called “viscoelastic phase separation” to form a mesh-like porous anchor layer with nanometer- to micrometer-sized pores (a printable porous anchor [PPA]) by merely coating a solution and drying it (Figure (a), top). With this PPA, the team achieved a bonding strength exceeding 7 megapascal (MPa) in an experiment using a flexible polymer with low adhesion to glass (Figure (b)). The PPA achieves a strong bond by a hybrid approach of bonding to the glass through chemical affinity, while physically interlocking with the polymer by causing the polymer to be incorporated into its tiny pores.

The bonding method using the PPA proposed in this study breaks away from the conventional case-by-case approach of developing an adhesive compatible with the materials on both sides, and holds the potential to serve as a platform capable of accommodating a wide variety of material combinations. With the aim of further expanding versatility, the team is currently pursuing two approaches to developing porous anchor layers: imparting conductivity to ensure heat dissipation and electrical connectivity at bonded interfaces, and using highly heat-resistant materials capable of withstanding harsh environments. As a result, this technology is expected to meet the diverse bonding needs of the industrial sector and to expand design flexibility in manufacturing processes in the fields of next-generation mobility, wearable devices, and soft robotics, where the use of multi-material structures will become essential in the future.

• This project was conducted by Shunto Arai (Independent Researcher, Research Center for Macromolecules and Biomaterials, NIMS).
• This research result was published online in Small on September 10, 2026.