Magnetically Actuated Nanorod Arrays as Biomimetic Cilia

We present a procedure for producing high-aspect-ratio cantilevered micro- and nanorod arrays of a PDMS−ferrofluid composite material. The rods have been produced with diameters ranging from 200 nm to 1 μm and aspect ratios as high as 125. We demonstrate actuation of these superparamagnetic rod arrays with an externally applied magnetic field from a permanent magnet and compare this actuation with a theoretical energy-minimization model. The structures produced by these methods may be useful in microfluidics, photonic, and sensing applications.