Wrinkling patterns of tantalum films on modulus-gradient compliant substrates

Wrinkling patterns are ubiquitous in nature and they are beneficial for a wide range of practical applications. Here we report on the wrinkling patterns in tantalum films sputter deposited on modulus-gradient compliant polydimethylsiloxane substrates. It is found that the sputtering process generates intrinsic and thermal compressive stresses, which are relieved by formation of locally ordered (herringbone) but overall disordered (labyrinth) wrinkling. The wrinkle sizes are strongly dependent on the substrate stiffness and film thickness. The formation mechanisms and evolutional behaviors of the wrinkling patterns have been discussed and analyzed in detail based on the continuum elasticity theory. Some potential applications of gradient wrinkling including surface hydrophobicity and measurement of substrate modulus are also presented in this paper.