Bacterial Magnetic Particles for Potential Applications in Nanoscale NDT&E

Current NDT techniques are capable of identifying sub millimetre defects in structural materials. Nanoscale NDT however, necessitates development of new techniques for identifying and sizing surface and more importantly subsurface imperfections. The reliability of micro and especially nano scale components heavily depends on such new developments. This paper presents a first attempt to explore the potential of magnetotactic bactreria for applications in NDT&E. Such bacteria having dimensions of a few microns can form single crystals of iron magnetite encapsulated in a magnetosome membrane. Crystals are structured in a long chain arrangement and polarised in the north / south direction, thus allowing the bacteria microorganisms to behave as magnets. Since their discovery in the 70s, different magnetotactic bacteria morphologies producing various magnetic minerals have been observed and a few have been successfully cultured. At present, emphasis is placed on understanding the mechanism of magnetic synthesis and associated crystalline structure behaviour, while a few applications are beginning to emerge. Such applications include magnetic storage devices, cell separation and magnetic resonance imaging (MRI).