Nondestructive testing in microfabrication using bacteria

Abstract

Micromanufacturing has increased rapidly at scientific, technological and industrial levels. However, this evolution has not been followed by a parallel development of Non Destructive Testing (NDT) techniques. The available techniques are, generally, unable to detect microdefects. In this work, two types of microgeometries were produced by Micro Powder Injection Molding (μPIM) of stainless steel AISI316L: specimens for tensile tests (simple geometry) and microscrews (complex geometry). During the process optimization, different injection conditions of temperature and pressure were tested, as well as various temperatures for thermal debinding and sintering. Throughout the process, detectable and undetectable defects by NDT techniques were produced, which were used in the assays to assess the role of bacteria in the detection of defects. After adding bacterial suspensions of Staphylococcus aureus or Rhodococcus erythropolis cells, the microcomponents were subjected to magnetic or electric fields to facilitate mobility of bacteria towards the defects. This new methodology to detect defects produced during microfabrication can be a good solution for inspection of microdefects.