Biomachining: metal etching via microorganisms

Abstract

The use of microorganisms to remove metal from a workpiece is known as biological machining or biomachining, and it has gained in both importance and scientific relevance over the past decade. Conversely to mechanical methods, the use of readily available microorganisms is low-energy consuming, and no thermal damage is caused during biomachining. The performance of this sustainable process is assessed by the material removal rate, and certain parameters have to be controlled for manufacturing the machined part with the desired surface finish. Although the variety of microorganisms is scarce, cell concentration or density plays an important role in the process. There is a need to control the temperature to maintain microorganism activity at its optimum, and a suitable shaking rate provides an efficient contact between the workpiece and the biological medium. The system's tolerance to the sharp changes in pH is quite limited, and in many cases, an acid medium has to be maintained for effective performance. This process is highly dependent on the type of metal being removed. Consequently, the operating parameters need to be determined on a case-by-case basis. The biomachining time is another variable with a direct impact on the removal rate. This biological technique can be used for machining simple and complex shapes, such as series of linear, circular, and square micropatterns on different metal surfaces. The optimal biomachining process should be fast enough to ensure high production, a smooth and homogenous surface finish and, in sum, a high-quality piece. As a result of the high global demand for micro-components, biomachining provides an effective and sustainable alternative. However, its industrial-scale implementation is still pending.

Photoacoustic Imaging in Oxygen Detection

“…In wound healing [8], doctors may need to monitor the changes of the local oxygen levels to prevent tissue necrosis and estimate the healing potential. In biomachining processes, the redox state needs to be precisely controlled for high-quality metal removal by microorganisms [9,10].…”

The Influence of Accelerated UV-A and Q-SUN Irradiation on the Antibacterial Properties of Hydrophobic Coatings Containing Eucomis comosa Extract

“…Pollution is increasing day by day, and environmental laws are becoming more stringent. Therefore, companies need to transform to meet their traditional objectives of cost reduction and good product quality, but also make efforts to implement a green and innovative set of technologies [44,45]. There is a need to replace synthetic polymers with natural and biodegradable materials such as polylactic acid.…”

Simultaneous Culture and Biomachining of Copper in MAC Medium: A Comparison between Acidithiobacillus ferrooxidans and Sulfobacillus thermosulfidooxidans

“…Two main mechanisms (direct and indirect pathways) have been postulated to explain metal bioetching 7 . Regarding the direct mechanism, bacterial adhesion on metal surface allows the enzyme activity to be responsible for metal oxidation and dissolution 5 . Nevertheless, according to the literature, this process is not the priority pathway for zero-valence copper (Cu 0 ) biooxidation 6,8 .…”