About the sector - EUON
Manufacturing - Top-down - About the sector text
Top-down methods involve taking a larger bulk material and transforming it into nano-scale particles by using a significant amount of mechanical, thermal or chemical energy. These methods are generally used to create higher volumes of nanoparticles but are often a lot less controllable than bottom-up processes due to the energy or chemical input involved. This can lead to a broader range of nanoparticle sizes than if nanoparticles were produced from the bottom-up. However, the top-down approaches are often much more scalable than bottom-up methods.1
There are many different methods that fall under this category. Top-down manufacturing approaches include mechanical milling, lithography, etching, laser ablation, sputtering, the arc discharge method, electro-explosion, etc. The description of several common methods is provided below:
- Mechanical milling is a cost-effective method to produce nanomaterials from bulk material. It is effective in producing blends of different phases and nanocomposites. Ball-milled carbon nanomaterial is a novel class material that provide the opportunity to satisfy energy storage, energy conversion demands and environmental remediation.
- Lithography uses a focused beam of light or electrons to develop nanoarchitectures. The process can be divided into masked lithography (photolithography, nanoimprint lithography, soft lithography) and maskless lithography (scanning probe lithography, focused ion beam lithography, electron beam lithography). In masked nanolithography, nanopatterns are transferred over a large surface area using a specific template or a mask, whereas in maskless lithography, the process is carried out without a mask.
- Sputtering is a process where nanomaterials are produced by bombarding solid surfaces with high-energy particles, such as gas or plasma. It is an effective method to produce thin films. When this technique is used, the sputtered nanomaterial composition stays the same as the target material with fewer impurities. Also, it is more cost-effective than electron-beam lithography.
- Laser ablation process involves the generation of nanomaterials using a powerful laser beam hitting the target material. The source material or precursor vaporises because of the high energy of the laser irradiation, which results in the formation of nanoparticle. This process can be considered as a green technique, because it does not use stabilising agents or other chemicals.2
1 Critchley, L. (2019). Nanoparticle Manufacture - What Methods Are There? AzoNano. Available at: https://www.azonano.com/article.aspx?ArticleID=5122
2 Baig, N., Kammakakam, I., & Falath, W. (2021). Nanomaterials: A review of synthesis methods, properties, recent progress, and challenges. Materials Advances, 2(6), 1821-1871.