Superhydrophobic Surfaces Created by Elastic Instability of PDMS

Abstract

Lotus flowers, rose petals, some plant leaves and insects have a naturally super-hydrophobic surface. In fact, the surface of a Lotus leaf is covered by micro and nano structures mixed with wax, which makes its surface superhydrophobic. In microfluidics, superhydrophobicity is an important factor in the rheometers on a chip. It is also sought in other complex fluids applications like the self-cleaning and the antibacterial materials. The wettability of the surface of solid support can be modified by altering its chemical composition. This means functionalizing the interface molecules to different chemical properties, and/or forming a thin film on the surface. We can also influence its texturing by changing its roughness. Despite considerable efforts during the last decade, superhydrophobic surfaces usually involve, among others, microfabrication processes, such as photolithography technique. In this study, we propose an original and simple method to create superhydrophobic surfaces by controlling elastic instability of poly-dimethylsiloxane (PDMS) films. Indeed, we demonstrate that the self-organization of wrinkles on top of non-wettable polymer surfaces leads to surperhydrophobic surfaces with contact angles exceeding 150˝. We studied the transition Wenzel-Cassie, which indicated that the passage of morphology drops "impaled" to a type of morphology "fakir" were the strongest topographies.

Flexible piezocapacitive sensors based on wrinkled microstructures: toward low-cost fabrication of pressure sensors over large areas

“…Mismatch between the elastic moduli of the Ecoex bulk and silicate surface regions produced wrinkles. [16][17][18][19] Typical features of the cross-sectional images of the nonwrinkled, one-side wrinkled, and double-side wrinkled Ecoex templates prepared in our systems were clearly observed in the FE-SEM images shown in Fig. 1b-d.…”

Study of Hybrid Microscopic and Macroscopic Buckling in UV Treated PDMS

“…Above some threshold for the compression ratio (δ > δ c ), we observe the formation of sinusoidal wrinkles on the top of the PDMS characterized by a cylindrical symmetry and oriented perpendicular to the direction of maximum stress; for short exposure time, the sample remains flat [12], [15], [16]. In this study, we extended the exposure time UV/O 3 to three hours (180 mins); this procedure leads to macroscopic buckling (global undulation) too ( Figure 1, iv).…”

Biaxially Morphing Droplet Shape by an Active Surface

“…Surfaces with controllable wetting properties are of great potential in downstream applications such as water harvesting, [ 1,2 ] self‐cleaning, [ 3–5 ] surface coating, [ 6,7 ] adhesion [ 8–10 ] and microfluidic devices. [ 11–14 ] One strategy to facilitate controllable surface wetting is to develop surface topographies, [ 15–17 ] thereby enabling a desired liquid/solid interaction.…”