Fundamental Study on the Possibility of Biomachining

研究了在实际加工技术中不存在的生物加工的可能性。利用特殊的噬金属菌进行了金属的精密加工实验。首先，开发了化能无机营养细菌之一的氧化亚铁硫杆菌的培养物。基础实验表明，金属的机械加工基本上是可能的。我们将这种技术命名为“生物机械”。为了限定加工区域，使用光刻法在工件上形成光致抗蚀剂。工件在培养液中振荡时，去除深度随加工时间的延长而增加。对纯铁、纯铜和黄铜的去除率分别为14 μ m/hr、20 μ m/hr和18 μ m/hr。接下来，研究了电场或磁场的影响。当外加电场大小合适时，去除率提高，而外加磁场对去除率无影响。我们将这种技术命名为“电场辅助生物机械”。在电场辅助生物加工中，可以通过控制电场条件来控制去除深度，这在实际应用中是非常有用的。此外，当使用适当的工具电极时，可以加工指定区域。以上实验结果表明，细菌对金属的生物加工是基本可行的。将来对该细菌进行遗传学解释时，这些细菌可能是微机械加工领域中的自主控制微型机器人。预计这项研究将进一步发展。

The possibility of biological machining that doesn't exist in practical machining techniques is investigated in this study. The experiment of fine and precision machining of metals was done with peculiar bacteria that eat metal. First, the culture of tiobacillus ferrooxidans that is one of chemolithotrophic bacteria was developed. The basic experiment showed that the machining of metals was fundamentally possible. We named this technique "biomachining". In order to define the machining area, the photo-resist was formed on the workpiece using photolithography method. The removal depth increased with the machining time when the workpiece was shaked in the cultured fluid. The removal rate for pure iron, pure copper and brass were 14mum/hr, 20mum/hr and 18mum/hr respectively. Next the effects of electric field or magnetic field were investigated. When the proper electric field was given, the removal rate increased, while the magnetic field had no effect on the removal rate. We named this technique "electric field assisted biomachining". In the electric field assisted biomachining, we can control the removal depth by the electrical condition, which is very useful in practical use. Moreover, it is possible to machine the designated area when the proper tool electrode was used. The above experimental results made clear that the biomachining of metals by bacteria was basically possible. When the genetic explication of the bacteria will be done in future, these bacteria might be self-controlled micro robots in the field of micromachining. Further development of this research is expected.