Adaptive wettability-enhanced surfaces ordered on molded etched substrates using shrink film

Abstract

Superhydrophobic surfaces in nature exhibit desirable properties including self-cleaning, bacterial resistance, and flight efficiency. However, creating such intricate multi-scale features with conventional fabrication approaches is difficult, expensive, and not scalable. By patterning photoresist on pre-stressed shrink-wrap film, which contracts by 95% in surface area when heated, such features over large areas can be obtained easily. Photoresist serves as a dry etch mask to create complex and high-aspect ratio microstructures in the film. Using a double-shrink process, we introduce adaptive wettability-enhanced surfaces ordered on molded etched (AWESOME) substrates. We first create a mask out of the children’s toy ‘Shrinky-Dinks’ by printing dots using a laserjet printer. Heating this thermoplastic sheet causes the printed dots to shrink to a fraction of their original size. We then lithographically transfer the inverse pattern onto photoresist-coated shrink-wrap polyolefin film. The film is then plasma etched. After shrinking, the film serves as a high-aspect ratio mold for polydimethylsiloxane, creating a superhydrophobic surface with water contact angles >150° and sliding angles <10°. We pattern a microarray of ‘sticky’ spots with a dramatically different sliding angle compared to that of the superhydrophobic region, enabling microtiter-plate type assays without the need for a well plate.

Flexible shrink-induced high surface area electrodes for electrochemiluminescent sensing

“…The photoresist layer was removed using acetone. Patterned Au and PO films were then lifted from their Si wafer supports and heated past the PO glass transition temperature (125 uC) using a commercial heat gun (Steinel HL1820S), shrinking the patterned electrodes by 95% within seconds 20,27 ( Fig. 2A-C).…”

“…It has been previously shown that heterogeneous, rough structures create anti-wetting behavior. 20,30 Additionally, creating large contrast between surface energies on a single substrate allows precise spatial control of small liquid volumes. 20 The contrast between patterned Au thin films and exposed PO areas allows for the same effect.…”

The Effect of Encapsulation on Crack-Based Wrinkled Thin Film Soft Strain Sensors

“…The metal-deposited SMP was then heated past its glass transition temperature (100 °C) in a convection oven set to 140 °C for 13 min, causing it to shrink roughly 67% in area [ 23 ]. The stiffness mismatch between the metallic thin film and the substrate causes the film to buckle and form hierarchical wrinkled structures [ 24 ]. The sample is then immersed in a 5 mM (3-mercaptopropyl) trimethoxysilane (95% MPTMS) ethanol solution for 1 h at room temperature to functionalize the Au surface.…”

Enhanced emission of fluorophores on shrink-induced wrinkled composite structures

“…Moreover, such wrinkle structures have been extensively characterized and leveraged for various applications [40–42, 44, 47–54]. Recent work has even shown that the wrinkles can be somewhat deterministic [47].…”

“…When the shrink film retracts, the thin stiffer metal films buckle to create ‘wrinkle’ structures [40–44]. This film shrinks considerably more than previously reported and thus results in significantly smaller structures [45–47].…”