Superparamagnetic photocurable nanocomposite for the fabrication of microcantilevers

We present a photocurable polymer composite with superparamagnetic characteristics for the fabrication of microcantilevers. Uniform distribution and low particle agglomeration (<50 nm) in the photocurable polymer matrix SU-8 are achieved by using superparamagnetic nanoparticles with a surfactant. Particles and composite are characterized by a transmission electron microscope, UV-VIS spectrometer and magnetic measurements. The composite contains 5 vol.% (18 wt.%) of Fe 3 O 4 nanoparticles with diameters of 12.1 ± 3.5 nm. The composite exhibits a magnetization saturation of 13.2 kA m −1 . Superparamagnetic composite microcantilevers with typical dimension of 2 µm × 14 µm × 80–300 µm are successfully fabricated by two conventional photolithography steps and a sacrificial layer etch. Exposure doses of 10 000 mJ cm −2 must be applied for microcantilever thicknesses of 1.8 µm due to the high UV absorption of the particles in the composite. The magnetic polymer cantilevers are successfully actuated in resonance in air with an amplitude of 29 nm. An off-chip coil is used to generate a magnetic field to actuate the cantilevers.