Superparamagnetic photocurable nanocomposite for the fabrication of microcantilevers

Abstract

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 Fe3O4 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.

A photopatternable superparamagnetic nanocomposite: Material characterization and fabrication of microstructures

“…The composite is treated by ultrasonic sound (Vibracell VCX 600 Sonics & Materials Inc.) for 20 min and then spin-coated onto a support glass wafer. The microfabrication process has been previously detailed [23].…”

“…However, there are limitations of the particle concentration in the composite caused by UV-light absorption of the magnetite particles. The dependence of the transmittance on the composites' thickness is presented elsewhere [23]. Here, the Table 2. UV/VIS-transmittance of the composite with different particle concentration was investigated (Fig.…”

“…13(a) shows the top and Fig. 13(b) the bottom side of a fabricated cantilever tip containing 5 vol.% magnetite particles, an exposure dose D of 10 J cm −2 , and a thickness of 1.8 m [23]. The UV transmittance of the composite layer is 8% at 365 nm and 21 % at 405 nm (Fig.…”

“…Additionally, the composites' feature resolution and its surface polarity is analyzed since the wettability of the surface will determine the further material functionalization. While the details of the microstructure fabrication process and the remote magnetic actuation of the composite cantilevers have been previously investigated [23], here, we investigate further the influence of particle concentration on the fabrication process. Due to UV-absorption of the particles in the composite, the exposure dose of the composite must be adjusted for each particle concentration.…”

Inkjet Printing of High Aspect Ratio Superparamagnetic SU-8 Microstructures with Preferential Magnetic Directions

“…The fabrication of magnetic microactuators by maskless photolithography based on photopolymer containing superparamagnetic nanoparticles (NP) has been recently demonstrated by Kim et al [13]. Suter et al have developed an SU-8-based superparamagnetic composite (SPMPC) containing Fe 3 O 4 NP presented in [14] which enables actuation, shown by Ergeneman et al [15], and compatible with both shadow-mask photolithography [16,17] and two-photon polymerization as shown Peters et al [18].…”