Hemp-Based Sustainable Slippery Surfaces: Icephobic and Antithrombotic Properties

Abstract

With the passage of the 2018 Farm Bill that removed hemp from the Controlled Substances Act altogether, production of hemp is experiencing a renaissance. Building on this revival and re-emergence of hemp, we designed and fabricated hemp-based sustainable and robust slippery surfaces by coating hemp paper with beeswax and subsequently infusing it with hemp oil. A wide variety of aqueous liquids and beverages easily slide on our hemp-based sustainable slippery surfaces, without leaving a trace. We also fabricated hemp-based sustainable slippery surfaces using different textured metals. Our hemp-based sustainable slippery metal surfaces display good icephobic and antithrombotic properties. With these attributes, we envision that our hemp-based sustainable slippery surfaces will pave the path to more safe, non-toxic, and biodegradable or recyclable slippery surfaces for applications in food packaging, anti-icing or de-icing coatings, and antithrombotic medical devices.

Keywords: antithrombotic property; hemp-based sustainable slippery surface; icephobicity.

Figure 1.

Possible wetting states on a porous solid surface. (a) Dry porous solid surface in contact with air. (b) Porous solid surface infused with a lubricant. (c) Porous solid surface on which the lubricant is displaced by the contacting liquid. (d) Porous solid surface on which the lubricant is not displaced by the contacting liquid. (e) Contacting liquid droplet cloaked by the lubricant. (f) Contacting liquid droplet not cloaked by the lubricant.

Figure 2.

Hemp-based sustainable slippery surfaces. (a) Schematic depicting the fabrication of hemp-based sustainable slippery surfaces. (b,c) SEM images showing the morphology of the hemp paper and the hemp paper coated with beeswax, respectively. Insets show SEM images at a higher magnification. (d) A 20 μL water droplet (colored red) sliding on a hemp-based sustainable slippery surface tilted by 4° relative to the horizontal. (e) Sliding angles of 20 μL droplets of water and aqueous beverages including Gatorade (∼68 mJ/m²), honey (∼60 mJ/m²), milk (∼55 mJ/m²), Coca-Cola (∼49 mJ/m²), and agave syrup (∼45 mJ/m²).

Figure 3.

Anti-icing nature of hemp-based sustainable slippery metal surfaces. (a) Schematic depicting the fabrication of hemp-based sustainable slippery metal surfaces. (b) Sliding angles of 20 μL water droplets on hemp-based sustainable slippery metal surfaces. (c) Water droplet adhering and freezing on as-received aluminum (left of the red dashed line) and sliding without freezing on a hemp-based sustainable slippery aluminum surface (right of the red dashed line). Surface temperature was −20 °C.

Figure 4.

Antithrombotic nature of hemp-based sustainable slippery titania surface. (a) A 20 μL whole blood droplet sliding on a hemp-based sustainable slippery titania surface. (b–d) Fluorescence microscopy images depicting adhesion of platelets (green) on the as-received titanium surface, titania nanotube surface (without hemp oil), and hemp-based sustainable slippery titania surface, respectively. (e,f) Number of platelets per unit area and LDH cytotoxicity, respectively, on the as-received titanium surface, titania nanotube surface (without hemp oil), hemp-based sustainable slippery titania surface, positive control (blood plasma without contact with any sample), and negative control (blood plasma with 10% triton-X100 to ensure maximum release of LDH).