Facile preparation of patterned petal-like PLA surfaces with tunable water micro-droplet adhesion properties based on stereo-complex co-crystallization from non-solvent induced phase separation processes

A facile method to prepare rose petal-like quasi-superhydrophobic poly(lactide) (PLA) membrane surfaces with tunable water droplet adhesion properties based on the stereo-complex co-crystallization of PLAs via non-solvent induced phase separation processes is reported. The co-crystallization of the D- and L-enantiomer of PLA on the bottom surfaces contacting the base glass has led to the formation of hierarchical microstructures containing half-developed to well-developed micrometer-scale papilla or spheres and nanometer-scale folds depending on the thickness of the primary membranes. The bottom surfaces of thinner PLA membranes with primary thicknesses of 100-200 micrometers containing half-developed smaller microspheres and a wider gap space could firmly pin water droplets even upside down with an extremely high adhesion force of about 118-132 mu N with water drop breakup, while the bottom surfaces of thicker PLA membranes with a primary thickness of 300-500 micrometers containing larger well developed microspheres with narrower gap space could allow the rolling of water droplets with lower adhesion forces of 74-99 mu N. Strategies were developed to create patterned PLA quasi-superhydrophobic membrane surfaces with zoned water droplet adhesion properties for controllable micro-droplet transportation and potentially image encrypting applications.