Self-healing Biological Molecules for Use in Engineering Materials

Phospholipid molecules are one of the fundamental building blocks of cell membranes in living organisms. These molecules are amphipathic with two hydrophobic fatty acid chains (tails) linked to a phosphate containing hydrophilic group (head) by a glycerol molecule. A bilayer lipid membrane (BLM), which is two phospholipids thick, is a 6-10 nm thick membrane and can be used to seal a porous material that has water on both sides. This paper presents how a specific phospholipid, 1-Stearoyl-2-Oleoyl-sn-Glycero-3Phosphocholine (SOPC), is used to seal a single square aperture (25 x 25 μm) of a silicon substrate. The phospholipids are able to self-assemble into organized structures in the presence of water and will form a bilayer across the aperture when deposited on the aperture and substrate and inundated in water. Mechanical failure is induced using a pressure gradient across the substrate and upon failure the amphipathic nature of the phospholipids reconstructs the failed BLM and seals the aperture thus, introducing the concept of a self-healing biological molecule. This paper will also present testing done on a BLM formed using a method called the Droplet Interface Bilayer (DIB). This method uses water droplets placed in oil to form a monolayer of phospholipids around the droplets. Once the monolayer is formed around the droplet, a bilayer can be formed by connecting two droplets.