Magnetic micropillars as a tool to govern substrate deformations

Magnetic actuated microdevices can be used to achieve several complex functions in microfluidics and microfabricated devices. For example, magnetic mixers and magnetic actuators have been proposed to help handling fluids at a small scale. Here, we present a strategy to create magnetically actuated micropillar arrays. We combined microfabrication techniques and the dispersion of magnetic aggregates embedded inside polymeric matrices to design micrometre scale magnetic features. By creating a magnetic field gradient in the vicinity of the substrate, well-defined forces were applied on these magnetic aggregates which in turn induced a deflection of the micropillars. By dispersing either spherical aggregates or magnetic nanowires into the gels, we can induce synchronized motions of a group of pillars or the movement of isolated pillars under a magnetic field gradient. When combined with microfabrication processes, this versatile tool leads to local as well as global substrate actuations within a range of dimensions that are relevant for microfluidics and biological applications.