Figure 1.
Process flow of the superhydrophobic substrates formed from shrink film paired with their respective CA.
(i) PO film is plasma treated with oxygen for 30 seconds (ii) Treated PO film is sputter coated with 60 nm of silver and 60 nm of gold (iii) PO film is shrunk at 160°C to induce buckling and folding (iv) PDMS is poured over fully shrunk PO film for casting (paired photo features flat PDMS) (v) Superhydrophobic PDMS cast is removed from shrunk PO (vi) Hard plastics are casted into superhydrophobic PDMS mold by applying pressure and heat (paired photo features flat PC) (vii) Superhydrophobic PC casted from superhydrophobic PDMS.
Figure 2.
Top down SEM images and AFM of the structurally modified surfaces' multiscale structures were taken.
Features are shown in (A) shrunk, bimetallic PO, (B) transferred in PDMS, and (C) imprinted in PS from PDMS. Scale bar is 10 µm for the large SEM images and 2 µm for the insets. (D) AFM 3D image of the morphology and height profile.
Figure 3.
Graphs depicting CA and SA for the structurally modified surfaces compared to flat.
(A) Contact angle measurements of structurally modified and flat PDMS, PS, PC, and PE. (B) Sliding angle measurements of structurally modified and flat PDMS, PS, PC, and PE. +represents measurements >90°.
Figure 4.
The low SA of superhydrophobic PDMS allows the water droplet to easily roll off the surface.
(A–C) A droplet being placed on the surface of superhydrophobic PDMS retracts onto the dropper. (D–F) A droplet rolling off the same surface immediately after placement at a 5° angle.
Table 1.
Calculated values of the solid fraction (Φ) were found using the average flat CA (θY) and the average structurally modified CA (θC).
Figure 5.
PS, PC, and PE structured and flat substrates were contaminated with a bacteria solution and either rinsed or not rinsed.
The resulting bacterial growth can be observed in each plate in the form of colonies following 24 hour incubation. (A) Substrates were rinsed with 50 µL of PBS after bacteria solution was deposited on the surface. (B) Substrates were not rinsed.
Table 2.
CFU counts for structured versus flat surfaces.