<p>Many uses of emulsion droplets require precise control
over droplet size and shape. Here we report a ‘shape-memorable’ micro-droplet
formulation stabilized by a polyethylene glycol (PEG)-modified
protein-surfactant, the droplets are stable against coalescence for months and
can maintain non-spherical shapes for hours, depending on the surface coverage
of PEGylated protein. Monodisperse droplets with aspect ratios ranging from 1.0
to 3.4 were controllably synthesized with a flow-focusing microfluidic device.
Mechanical properties of the interfacial protein network were explored to
elucidate the mechanism behind the droplet shape conservation phenomenon.
Characterization of the protein film revealed that the presence of a PEG layer
at interfaces alters the mechanical responses of the protein film, resulting in
interfacial networks with improved strength. Taking advantage of the prolonged
stabilization of non-spherical droplets, we demonstrate the possibility of
functionalization of the droplet interface with accessible biotin moieties. The
stabilization of micro-droplet shape with surface-active proteins that also
serve as an anchor for integrating functional moieties, provides a tailorable
interface for diverse applications.</p>
Droplet shape control using microfluidics and designer biosurfactants
