Unidirectional Pore Formation in Resins Using a Magnetic-Nanoparticle-Chain Template

We present a novel manufacturing technique for generating unidirectional pores in ultraviolet (UV)-curable resins using self-assembled magnetic nanoparticles (MNPs) with chain-like structures. The method utilizes two templation mechanisms for pore formation: the UV-masking effect of the MNP chains and the physical presence of MNP chains themselves. Fe
₃
O
₄
nanoparticles and PAK-01 were used as the template and UV-curable resin, respectively. Unidirectional pores formed only when resin/MNP mixtures were cured under a strong externally applied magnetic field. Water absorption tests indicated that some of the unidirectional pores were through-hole-type pores. The pores were cylindrical with an ellipsoidal cross-section. When the UV irradiation angle (
θ
) was 30°, the long and short diameters of the pores were approximately 9 and 8
$\mu$
m, respectively, before MNP removal, and 12 and 8
$\mu$
m, respectively, after removal. After MNP removal, the ellipticity of the pores in the samples increased from 1.5 to 2.4 with the increase in
θ
because of the increased UV-masking effect of the MNP chains.