AFM imaging

The DPPC monolayer was Langmuir-Blodgett transferred from the droplet surface by lifting a small piece of freshly peeled mica sheet across the air-water interface of the droplet at a rate of 1 mm/min. For adsorbed DPPC films or DPPC films spread from the aqueous suspension (Protocols 1 and 2), before the Langmuir-Blodgett transfer, vesicles in the droplet were displaced with buffer using a subphase replacement technique (44). The immobilized DPPC films were scanned using an Innova AFM (Bruker, Billerica, MA) in air in contact mode using a silicon nitride cantilever with a spring constant of 0.12 N/m and a tip radius of 2 nm. Image analysis was conducted with Nanoscope Analysis (ver1.5).