Small-scale thin film experiments can provide models for large-scale engineering applications

October 2009


Thin films are omnipresent in daily life as mirrors and other optical coatings, rolls of adhesive tape and microstructures for semiconductors. They’re also critical for many civil and environmental engineering applications. Paint on steel, concrete shells on domed buildings, fiberglass-polymer wrapping on concrete bridges, seals for toxic waste and solar voltaic films on roofs all have geometric properties similar to thin films: a thin coating covering a large area. And all are prone to delamination, blistering, folding or cracking. In effect, thin films present enormous difficulties because of their propensity to resist deformation when the substrate expands or contracts.


MIT researcher Pedro Reis studies the fundamentals of thin film behavior at the laboratory scale by treating the thin films and substrates as nonlinear systems prone to fracture or delamination. To create these behavioral models of large-scale thin-film applications, Reis scales them down to well-controlled desktop-sized experiments that preserve the behavior of the larger systems. He achieves this by identifying invariants based on geometry and fracture or delamination properties. He has applied this research method to three notable thin film-substrate systems: the tearing of thin films as a fracture-adhesion process; the delamination mechanics of thin fi