Preferred deposition of phospholipids onto ferroelectric P(VDF-TrFE) films via polarization patterning

Abstract

Ferroelectric polarization can be used to assemble various organic and inorganic species and to create nanostructures with controlled properties. In this work, we used poly(vinylidene fluoride-co-trifluoroethylene) P(VDF-TrFE), ultrathin films deposited by the Langmuir–Blodgett technique as templates for the assembly of various phospholipids, which are the essential components of cell membranes. It was observed that 1,2-di-O-hexadecyl-sn-glycero-3-phosphocholine phospholipids (DHPC) form self-assembled structures (molecular domains) on bare P(VDF-TrFE) surfaces. These were revealed by the formation of homogeneous and stable rounded blobs with diameters in the range 0.5–3 µm. Further, ferroelectric polymer films were polarized by the application of various voltages via a conducting tip using a piezoresponse force microscopy (PFM) setup and PFM images were obtained showing controlled polarization distribution. After this, the phospholipid molecules were deposited from the solution. Conventional atomic force microscopy experiments were then performed to assess the selectivity of the deposition process. It was observed that the deposition process is very sensitive to the concentration of the solution. The selective deposition was observed mainly at the polarization boundaries where the selectivity reached a maximum value of about 20–40%. In this way, the controlled assembly of organic molecules on the polymer surfaces could be achieved. In addition, the PFM tips could be functionalized by the phospholipids and switchable lines of the DHPC molecules on the P(VDF-TrFE) surface were then visualized by PFM.