This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The National Institute for Materials Science has developed a technology to strongly bond dissimilar materials by using a porous layer, formed by a solution-coating and drying process, as an anchor. The research team confirm that even materials that are normally difficult to bond together can be bonded with a strength exceeding 7 MPa by adopting a hybrid approach: adhering to one material through chemical affinity and bonding to another via physical interlocking using tiny pores.
The work is published in the journal Small. 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. Conventionally, an adhesive compatible with each material combination needed to be designed and developed. Bonding strength can also be enhanced by roughening the surface of a substrate via mechanical scratching or chemical etching.
However, this method raises energy consumption and environmental concerns, including increased manufacturing complexity and the generation of processing residues. In this study, the research team 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 coating a solution and drying it.
With this PPA, the team achieved a bonding strength exceeding 7 megapascals (MPa) in an experiment using a flexible polymer with low adhesion to glass. The PPA achieves a strong bond through a hybrid approach: bonding to the glass through chemical affinity while physically interlocking with the polymer by incorporating it into the layer's tiny pores. The PPA bonding method proposed in this study breaks away from the conventional case-by-case approach of developing an adhesive compatible with the materials on both sides.
It has the potential to serve as a platform capable of accommodating a wide variety of material combinations. To further expand versatility, the team is 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. This technology is expected to meet the industrial sector's diverse bonding needs and expand design flexibility in manufacturing processes for next-generation mobility, wearable devices and soft robotics, where multi-material structures will become essential in the future.
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