Figure 2. Programming the morphology of the flagelled soft micromachines.

(a) Formation of compound micromachines with a bilayer head and monolayer tail. Due to lack of particle alignment, the folding axis of the head is solely determined by the edge effect. Finite element modelling (FEM) simulations visualize internal stress distribution. (b) By reinforcing the magnetic nanoparticles (MNPs) inside the supporting layer, the folding of the head can be decoupled from the geometric effects and directly controlled by the particle alignment. Scale bars, 500 μm. The final 3D shape of the helical structures after autonomous folding of hydrogel (c) bilayers and (d) monolayers is controlled by the alignment of embedded MNPs. The orientation of MNPs alignment (denoted by α) generates a helical angle (denoted by θ) given by θ=90°−α in bilayer structures and θ=α in monolayer structures. Scale bars, 1 mm.