Biomachining is the

machining Machining is a manufacturing process where a desired shape or part is created using the controlled removal of material, most often metal, from a larger piece of raw material by cutting. Machining is a form of subtractive manufacturing, which util ...

process of using lithotropic

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

to remove material from metal parts, contrasted with chemical machining methods such as

chemical milling Chemical milling or industrial etching is the subtractive manufacturing process of using baths of temperature-regulated etching chemicals to remove material to create an object with the desired shape. Other names for chemical etching inclu ...

and physical machining methods such as

milling Milling may refer to: * Milling (minting), forming narrow ridges around the edge of a coin * Milling (grinding), breaking solid materials into smaller pieces by grinding, crushing, or cutting in a mill * Milling (machining), a process of using ro ...

. Certain bacteria, such as Thiobacillus ferrooxidans and Thiobacillus thiooxidans, which are also used in the mineral refinement process of

bioleaching Bioleaching is the extraction or liberation of metals from their ores through the use of living organisms. Bioleaching is one of several applications within biohydrometallurgy and several methods are used to treat ores or concentrates containing ...

, utilize the chemical energy from oxidation of iron or copper to fix carbon dioxide from the air. A metal object, when placed in a culture fluid containing these metal-metabolizing bacteria, will have material removed from its surface over time. Biomachining is ideal for micromachining due to its very low

material removal rate Material removal rate (MRR) is the amount of material removed per time unit (usually per minute) when performing machining operations such as using a lathe or milling machine. The more material removed per minute, the higher the material removal ...

. In addition, biomachining is less likely to leave an undesirable

surface finish Surface finish, also known as surface texture or surface topography, is the nature of a interface (matter), surface as defined by the three characteristics of lay, surface roughness, and waviness.. It comprises the small, local deviations of a ...

; neither chemical nor physical energy is concentrated on the cutting area, so the possibility of a damaged or burned surface is slim. This process has been successfully used to cut both pure iron and pure copper.

Process

Biomachining is performed in a manner similar to

: the area to be cut is marked out as a negative image with an inert maskant, used to protect the areas that are not to be cut. The part is then dipped into a bath of culture fluid, which is kept at a precise temperature and stirred throughout the process. Laboratory experiments on the subject have determined that the depth of any cuts produced increases as the stirring rate increases; this depth is also affected by the temperature of the process.

Sources

* Machining {{metalworking-stub