UK-based TWI Ltd., in collaboration with the University of Cambridge in the UK, has developed a novel welding technique to create what TWI says is the world’s smallest weld in thermoplastic material.
Research by TWI and the Univeristy of Cambridge’s Cavendish Laboratory into precise patterning of laser absorber dye on a plastic surface to define weld position lead to the latest advance that create the new technique that enables welds with a width smaller than 10 microns.
With polymethyl methacrylate (PMMA) thermoplastic as a base material, the team carried out trials, following the principle of transmission laser welding using a thin coating of infrared absorbent material at the joint interface. The coating was patterned using electron beam lithography to the required resolution in a reproducible manner, so it could be retained after welding. Joint strength was ratified using larger-scale samples.
The trials culminated in successful demonstration of a series of laser welded joints with widths of 1 μm and channels of 5 μm. Smaller welds with 0.5 μm were also demonstrated leading to the conclusion that it is possible to make plastics components with a high density of structure and resolution below 1 μm, and that welding can be applied without excessively heating regions outside the weld lines.