Microcrystal-like cellulose fibrils as the diamagnetic director for microfluidic systems

Abstract

In recent years, nanostructures and nanostructuring of biogenic materials have been studied intensively, with a view to “high-tech” applications of sustainable, biologically derived materials. Magnetic orientation is useful for creating industrial products. Techniques for diamagnetic alignment of materials using fields of several Tesla (T) or more have been reported. In the present study, we explore the optical characteristics of microcrystalline cellulose whisker (CW), under sub-Tesla magnetic fields. Our eventual target is to create a biogenic optical device. We isolated microcrystalline CWs with high aspect ratio using centrifugation and found that these anisotropic whiskers, when in an aqueous suspension, respond to sub-T order magnetic fields, as observed using an optical microscope and a spectrometer. During observations with dark-field illumination, we found that the scattered light intensity changed during the magnetic orientation process, and depended on the directions of the magnetic field and dark-field illumination. These oriented microcrystalline CWs can be bio-mimetic optical tools for microscale wet processes, such as bio-MEMS.