Magnetoelastic actuation of superparamagnetic nanoparticle membranes

The ability to manipulate bending and straining of thin material sheets remains an exciting challenge for reversible nano-scale actuation. While many thin materials are currently in use, most require modification to achieve actuation. In our experiments, we use freely suspended ~10nm thick membranes of self-assembled superparamagnetic nanoparticles. The membranes’ thinness and inherently soft elastic properties allow substantial elastic deformation. Geometric constraints to bending are controlled via the membranes’ boundary conditions along their perimeter or via introducing strain-releasing cuts with a focused ion beam. We find that an applied magnetic field can induce large, micron-scale deflections of the membranes, which we track in 3D with high-resolution confocal microscopy. Beyond a critical field strength we observe evidence of magnetoelastic buckling. We explore particle-scale magnetic effects with Magnetic Force Microscopy (MFM). Combining soft magnetism with soft elasticity, magnetoelastic nanoparticle membranes are a promising platform for reversible actuation of thin materials sheets in the presence of geometric constraints.