Micro-nano hierarchically patterned HDPE surfaces for repelling edibles, cosmetics and bacteria

Abstract

Approximately 15–20 % of edible liquid and cosmetic foods adhere to the packaging containers, causing significant product loss and requiring substantial fresh water for cleaning. We address this challenge by fabricating a hierarchical patterned high-density Polyethylene (HDPE) surface inspired by Lotus leaf. Micropillars (base diameter ~8 μm, pitch ~23 μm, height ~10 μm) were hot embossed on HDPE using a polydimethylsiloxane (PDMS) replica at 150 °C, 13 kPa for 5 min. They were subsequently coated with a ~2 μm thick carbon soot nano particulate layer (particle diameter ~60 nm) derived from burning camphor. These hierarchically patterned HDPE demonstrated excellent omniphobicity, repelling body lotion, milk, chocolate syrup, honey, ketchup and DI water droplets with static contact angles (SCAs) >145°, roll-off angles (RAs) <8° and contact angle hysteresis (CAH) <13°, similar to the Lotus leaf, which repels 17 commonly used liquids with SCAs >150°, RAs <10° and CAH <10°. Furthermore, applying a carbon soot coating to the transparent HDPE bottle reduced the sticking of residual body lotion from 30 wt% to 11 wt%. Moreover, the residual body lotion in uncoated, coated and hierarchically patterned HDPE opaque bottles is ~20 wt%, 7.4 wt% and 5.7 wt%. Hence, hierarchically patterned HDPE opaque bottles help minimize material waste by ~14 wt%, promoting a more sustainable packaging approach. Additionally, hierarchically patterned HDPE surfaces minimize Escherichia coli bacterial adhesion and induce bacterial cell damage, in contrast to unpatterned surfaces, which promote the formation of large bacterial colonies.