Self-assembled Supramolecular Structures Of Chiral Phospholipids: Structure, Mechanical Properties And Patterning

Lipid molecule is well known natural building block to form different supramolecular structures with specific shape, size and functionality. In my thesis work, I have used DC8,9PC 1,2-bis(tricosa-10,12-dinoyl)-sn-glycero-3-phosphocholine), a type of chiral lipid to form the vesicles, tubules and ribbons . By using Atomic Force Microscope, I have studied the morphological features of these particular structures. Also, the mechanical properties of lipid tubules have been studied using AFM. Softlithography has been used to pattern the lipid vesicles and tubules into 2-dimensional and 3-dimensional ordered arrays. The structure of self-assembled hollow spherical vesicles was studied using AFM. The applications of soft lithography in patterning polymerized lipid vesicles of DC8,9PC on glass substrates are reported. It has been demonstrated that the lipid vesicles can be used as a high-molecular weight ink to be transferred from a PDMS stamp onto a glass substrate to form two-dimensional stripes with a controlled separation over a large area. By combining channel flow with dewetting within microfluidic networks, vesicles were assembled into one-dimension lines on a glass substrate. The vesicle lines can also be selectively removed from the substrate with lift-up process. The direct and precise assembly of lipid vesicles on solid substrates will open up the possibility of integrating them in biosensors and microelectronic devices. Lipid tubules and helices are other extremely interesting superstructures that have captured the imagination of scientists in disciplines from biology through material science to chemistry and physics. Lipid tubules are self-assembled hollow cylindrical structures with opened ends, composed of rolled-up bilayers. They have been used as a template for the synthesis of inorganic materials, a substrate for the crystallization of proteins, a controlled release system for drug deliver, and a colorimetric material for chemical sensors. However, due to the high aspect ratio, the formation of ordered arrays of lipid tubules on substrates still remains to be challenging. In this thesis work, the application of well-known soft lithography techniques in assembling and manipulating lipid tubules on substrates has been reported. I show that lipid nano- and microtubules can be assembled into two-dimensional (2-D) parallel arrays with controlled separations by combining fluidic alignment with dewetting, which occur within microchannels. It has also been shown that lipid tubules can be assembled into 3-D crossbar arrays with fluidic alignment, which occurs within microfluidic networks. The deposition experiments with silica colloidal particles show that the 2-D parallel-aligned tubules can be used as a template to synthesize silica films with controlled morphologies and patterns on substrates in a single-step process. Atomic force microscopy studies show that the resulting silica films replicate the shape, orientation, and pattern of aligned tubule templates. Though, the structures of the lipid tubules have been extensively studied, but very little is known about their mechanical properties. In my work, the mechanical properties of the lipid tubules of DC8,9PC were studied with atomic force microscope. The deformation of the lipid tubules with different outer diameters is directly observed in both tapping and contact modes with increasing loading forces