Self-spreading behavior of supported lipid bilayer through single sub-100-nm gap

We report on the self-spreading behavior of a supported lipid bilayer passing through a sub-100-nm gap (nanogap). For this purpose, a device with a nanogap in a microchannel on a silicon substrate was designed and fabricated by electron beam lithography and photolithography. Fluorescence images of the lipid bilayer labeled with dye-conjugated lipids were observed by using a confocal laser scanning microscope. The time evolution of the self-spreading lipid bilayer passing through the nanogap was investigated at first. In the device, the lipid bilayer successfully passed through the nanogap without any stagnation. An analysis of the velocity of an advancing lipid bilayer showed no significant effect before or after passage though the nanogap. The effects of dye-conjugated lipid molecules and the size of the nanogap on the self-spreading behavior were examined next. We observed an abrupt decrease in the fluorescence intensity in the vicinity of the nanogap with Texas Red-DHPE and fluorescein-DHPE. It was revealed that the decrease depends on nanogap size as well as bulkiness of the dye molecule. The results suggest that bulkier dye molecules experience interference when they pass through narrower nanogaps.