Synthesis of wrinkle-free metallic thin films in polymer by interfacial instability suppression with nanoparticles

Synthesis of a smooth conductive film over an elastomer is vital to the development of flexible optics and wearable electronics, but applications are hindered by wrinkles and cracks in the film. To date, a large-scale wrinkle-free film in an elastomer has yet to be achieved. We present a robust method to fabricate wrinkle-free, stress-free, and optically smooth thin film in elastomer. Targeting underlying mechanisms, we applied nanoparticles between the film and elastomer to jam the interface and subsequently suppress interfacial instabilities to prevent the formation of wrinkles. Using polydimethylsiloxane (PDMS) and parylene-C as a model system, we have synthesized large scale (>10 cm) wrinkle-free Al film over/in PDMS and demonstrated the principle of interface jamming by nanoparticles. We varied the jammer layer thickness to show that, as the layer exceeds a critical thickness (e.g., 150 nm), wrinkles are successfully suppressed. Nano-indentation experiments revealed that the interface becomes more elastic and less viscoelastic with respect to the jammer thickness, which further supports our assertion of the wrinkle suppression mechanism. Since the film was embedded in a polymer matrix, the resultant film was highly deformable, elastic, and optically smooth with applications for deformable optical sensors and actuators.Synthesis of a smooth conductive film over an elastomer is vital to the development of flexible optics and wearable electronics, but applications are hindered by wrinkles and cracks in the film. To date, a large-scale wrinkle-free film in an elastomer has yet to be achieved. We present a robust method to fabricate wrinkle-free, stress-free, and optically smooth thin film in elastomer. Targeting underlying mechanisms, we applied nanoparticles between the film and elastomer to jam the interface and subsequently suppress interfacial instabilities to prevent the formation of wrinkles. Using polydimethylsiloxane (PDMS) and parylene-C as a model system, we have synthesized large scale (>10 cm) wrinkle-free Al film over/in PDMS and demonstrated the principle of interface jamming by nanoparticles. We varied the jammer layer thickness to show that, as the layer exceeds a critical thickness (e.g., 150 nm), wrinkles are successfully suppressed. Nano-indentation experiments revealed that the interface becomes more elastic and less viscoelastic with respect to the jammer thickness, which further supports our assertion of the wrinkle suppression mechanism. Since the film was embedded in a polymer matrix, the resultant film was highly deformable, elastic, and optically smooth with applications for deformable optical sensors and actuators.This research was partially supported by the Gulf of Mexico Research Initiative (GoMRI) under grant no. SA12-03/GoMRI-003, ARO under grant no. W911NF-20-1-0307, ONR under grant no. N00014-21-1-2834, and the Cancer Prevention Research Institute for Texas (CPRIT) under grant no. RP200593. Microfabrication and material characterization instrument was partially supported by ARO under grant no. W911NF-17-1-0371. Portions of this work were conducted in the Minnesota Nano Center supported by National Science Foundation under grant no. ECCS-1542202.This research was partially supported by the Gulf of Mexico Research Initiative (GoMRI) under grant no. SA12-03/GoMRI-003, ARO under grant no. W911NF-20-1-0307, ONR under grant no. N00014-21-1-2834, and the Cancer Prevention Research Institute for Texas (CPRIT) under grant no. RP200593. Microfabrication and material characterization instrument was partially supported by ARO under grant no. W911NF-17-1-0371. Portions of this work were conducted in the Minnesota Nano Center supported by National Science Foundation under grant no. ECCS-1542202