Engineering the Interface: Effects of Interfacial Adhesion and Substrate Thickness on the Ductility of Polymer-supported Metal Films

Abstract

Background Ductility of polymer-supported metal films is important for flexible electronic devices and it is strongly affected by the metal film, polymer substrate, and their interfacial properties. Objective In this paper, the effect of interfacial adhesion and substrate thickness on the metal film ductility was investigated. Methods Mechanical behavior of 500 nm-thick aluminum (Al) films deposited on polyethylene-terephthalate (PET) substrates with thickness of 12, 25, and 50 μm was studied by tensile testing with in-situ electrical resistance measurements and post-mortem scanning electron microscopy. In addition, plasma etching was applied to tailor the PET surface condition before Al film deposition. Subsequently, the Al/PET interfacial adhesion was quantitatively evaluated using the laser spallation approach. ResultsThe tensile tests showed that plasma etching improved the ductility of the Al films, and that the apparent ductility of the Al film on the 50 μm-thick PET substrate was substantially lower than that on the 12 and 25 μm PET thickness. Laser spallation results revealed that the plasma etching increased the Al/PET interfacial adhesion. Conclusions The influence of plasma etching and substrate thickness on the Al film ductility can be explained by the interface adhesion and shear lag theory. Plasma etching improves the interfacial adhesion by inducing both chemical and physical changes on the PET surface, and substrate thickness contributes to interface shear stress upon strain localization. The competing effect of the interfacial adhesion and the interfacial shear stress leads to a limiting substrate thickness for the desired ductility at a given tensile strain.

Sucrose-mediated formation and adhesion strength of Streptococcus mutans biofilms on titanium

“…Because the stress load is applied indirectly to the material interface through impingement of a pulsed laser on the back side of the specimen, laser spallation is valuable for characterizing bulk adhesion properties of a wide range of materials. Material interfaces as diverse as gels [ 32 ], laminated composites [ 33 ], thin metal films [ 34 , 35 ], polymer films [ 36 ], and mammalian cells on substrates [ 37 ] have been investigated using the laser spallation technique. The shock loading conditions are also used to quantify dynamic behaviors of materials [ 38 , 39 ] and in the development of stress-reporting materials [ 40 ].…”

Sucrose-mediated formation and adhesion strength of Streptococcus mutans biofilms on titanium

“…Because the stress load is applied indirectly to the material interface through impingement of a pulsed laser on the back side of the specimen, laser spallation is valuable for characterizing bulk adhesion properties of a wide range of materials. Material interfaces as diverse as gels [21], laminated composites [22], thin metal films [23, 24], polymer films [25], and mammalian cells on substrates [26] have been probed using the laser spallation technique. The shock loading conditions are also used to quantify dynamic behaviors of materials [27, 28] and in the development of stress-reporting materials [29].…”