Wrinkling of Thin PDMS Films on Ecoflex Substrates
Nanshu Lu (University of Texas at Austin)
Soft Materials and Structures
Mon 9:00 - 10:30
Barus-Holley 158
Wrinkling of thin stiff films on compliant substrates has been widely studied but the material systems are often limited to metal or ceramic thin films on elastomeric substrates. However, the film/substrate stiffness mismatch does not have to be very large. With the emergence of soft materials, wrinkling of a polymer film on a softer substrate has drawn more and more attention but systematic experimental investigation is still lacking. We study the wrinkling of thin PDMS films on soft Ecoflex substrates through both experimental and numerical methods. Ultra-violet ozone (UVO) treated PDMS film and pre-stretched Ecoflex substrate can be adhered through covalent bonding. Gradually relaxing the pre-strain in the Ecoflex substrate will induce wrinkling in the. Wrinkle profiles (amplification and wavelength) are quantified through optical profiler. Wrinkle density distribution has been employed to reveal the onset strain of wrinkling. The effect of film modulus and substrate thickness has been quantified. Both the film and the substrate can modeled as Neo-Hookean materials in finite element models (FEM). Buckling and post-buckling analysis are performed assuming perfect bonding between the film and the substrate. Winkling amplitude and wavelength output from FEM have found good agreement with experimental measurements. This work will provide important insights on the instabilities of both artificial and natural soft films.