Developments in micro- and nano-defects detection using bacterial cells

• New bacterial strains were used with magnetic fields, to improve bacteria mobility.
• Different materials and defect were tested: AISI 316L, AA1100 and NiTi.
• Bacterial cells allow identifying topographic surface attributes as roughness.
• Nano-indentation with 0.6 µm depth and 5.3 µm length were detected by bacteria.
• Cracks of about 0.5 µm wide in test block Type 1 ISO were successfully detected.

This paper describes improvements to the Nondestructive Testing (NDT) technique recently proposed, based on the use of bacterial cell suspensions to identify micro- and nano-surface defects. New bacterial strains were used with magnetic fields to improve bacteria mobility. Different materials and defect morphologies were tested, including nanoindentation defects, micro-powder injection moulding components and micro-laser welding. Nanoindentations with 0.6 µm depth and 5.3 µm side length were successfully detected. Bacterial cells allow identifying different topographic attributes of the surfaces, such as roughness. Cracks of about 0.5 µm wide and 10 µm depth in a reference test block Type 1 were successfully detected.

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