Fig. 3

Precise control in rolling direction towards helical microstructure construction. a The scheme of parallelogram-patterned nanomembrane with different microdroplet trigger point (I–V), FEM predictions, experimental results (optical images), and corresponding paper works (photographs) of six different microstructures. Dashed lines in the FEM model elucidate the sketch of partition in the quasi-static model. Scale bar (third column), 100 μm. Scale bar (forth column), 3 cm. b Schematic illustration of the definition of rolling angle θ and trigger point in parallelogram-patterned nanomembrane. Colorized edges depict different rolling behavior starting from the right bottom corner (orange) and right top corner (green). c Relation between rolling angle θ and trigger point. The diagram is divided into three regions according to different rolling behavior in a. The inset plots the relation between helical pitch and rolling direction. Error bars represent standard deviation