Use of wrinkles for fabrication of stretchable electrodes and omniphobic surfaces

Abstract

The buckling of stiff film on a substrate had been of great interest as this response happen spontaneously and is self-organizing. This provides an unconventional, scalable and easy way to fabrication surfaces with tunable structures from the range of nanometers to micrometers. We optimized a process to fabricate stretchable electrodes by transferring wrinkled gold onto elastomer. We tested their electrochemical sensing functionality through detection of glucose concentration with or without strain. Results showed that the stretchable electrodes provide high sensitivity for the detection of glucose (860 ± 60 µA/mM.cm2), comparable to electrodes before transfer. The current detected was also consistent under strain. Investigation of the resistance indicates that the electrode configuration under strain is important as current running parallel to direction of strain is much more affected under tension. We also developed a fast and facile process to fabricate surfaces that consisted of wrinkles and nanoparticles. Using such surfaces, we tested the omniphobicity effect of hierarchical structures consisting of wrinkles and nanoparticles. Results show that all the fluorinated structured surfaces were hydrophobic, ranging from water contact angle of 125° for wrinkled surfaces to 155° for hierarchical surfaces. The surfaces that were either wrinkled or decorated with nanoparticles were oleophilic with low hexadecane contact angles (~26° and ~55° respectively). The combination of both structures achieved oleophobicity of more than 110°. The effectiveness of nanoparticles for low surface tension liquid were due to its re-entrant like structure. The omniphobic surfaces were also shown to be repellent to blood (>135°), making it a potential material for use medical devices.