A dip coating method was developed to produce macroporous polymer films which were used as scaffolding for phospholipid biomembranes in which ion channels were reconstituted for proton gating and transport. This system was used to develop a functional biocomposite proton exchange membrane (PEM) because the dip coating process was found to be better suited to the reformation of ion channels than the breath figure and spin coating methodologies, two other macroporous film fabrication techniques. The dip-coating method produced macroporous polymer films with the highly ordered hexagonally packed spherical pore morphology needed for biomembrane stabilization. This method allowed reliable fabrication of continuous porous arrays that ranged from 0.5 to 12 um, with a relatively monodisperse diameter, since deviation was kept within 11%. Dip coated porous films served as functional scaffolding for biomembranes while providing dimensional and substrate flexibility not previously achieved or realized in other investigated techniques. Biomembranes, formed within the pores of the dip-coated films, provided great barrier properties to the transduction of ions and were stable upwards of 24 hours. Gramicidin ion channels reconstituted into the biomembranes exhibited transport properties with resistance values of 0.5 MOhm and displayed the desired selectivity to monovalent cations.
The surface modification of Nafion® was investigated as a manner to improve the functionality of a traditional PEM. Planar phospholipid membranes with reconstituted ion channels were used as functional coatings to improve the properties of Nafion®. It was found that the expansion of Nafion® when hydrated caused the failure of the biomembrane coating which made this a non-viable option.