**Author details**

by the cost of nanoparticles. Although the volume fraction of nanoparticles in MQL fluid is relatively small in each experimental research, it will be large when applied to production line in practice.

The cost-effective and sustainable manufacturing techniques are being given considerable importance these days to ensure economic, societal, and environmental sustainability globally. The basic parameters of nanofluids are discussed in detail, and they give strong effects on their tribological and lubricating characteristics, as well as the cost of NFs. The selection of appropriate nanofluids with suitable parameters is the crucial factor for machining processes. Especially for hard machining materials using geometrically defined cutting edges (hard turning, hard milling, hard drilling, and so on), the effectiveness of nanofluids is evaluated in terms of reducing the friction coefficient, enhancing the cutting performance, ensuring the tool life, and achieving good surface quality. However, very few records can be seen in the literature indicating that more experimental research is needed to find the optimal parameters

The successful application of nanofluids in MQL technique using vegetable oils becomes a big step toward sustainable manufacturing. This new trend is well suited to encounter the issue of environmental change. MQL machining under nanofluid condition significantly develops the cutting processes, which generate large amount of heat such as hard turning, hard milling, grinding, and so on. The machining capability and achieved surface integrity of hard cutting operations are much improved and equivalent to those of grinding, but the productivity is higher. They can replace or supplement to some of grinding processes. The progression of

Like the idea coming from composite materials, the use of hybrid nanofluids (two or more different types of nanoparticles suspended in fluids) recently gains much attention due to better performance when compared to nanofluids [63–65], but the ratio of mixing and the types of nanoparticles will be continually studied and proven. On the one hand, the MQCL technique, the novel development of the MQL technique will be the future of modern machining processes. MQCL technique has overcome the cooling effect, the main drawback of MQL method [66, 67]. MQCL technique with nanofluids or hybrid nanofluids definitely brings out novel solutions and develops hard machining and grinding to the new level in the near future. On the other hand, the development of ice jet machining is one of the greatest achievements in the field of modern/advanced machining. It is a nondestructive, nonabrasive, residue-free, and environmentally friendly way of machining [68].

in order to ensure maximum performance of using nanofluids in machining.

**4. The development trend of nanofluids**

hard machining will reach further achievements.

**Symbols and Abbreviations**

a<sup>p</sup> depth of cut (mm)

v cutting speed (m/min)

**3.5. Conclusion**

192 Microfluidics and Nanofluidics

Tran The Long\* and Tran Minh Duc

\*Address all correspondence to: tranthelong90@gmail.com

Department of Manufacturing Engineering, Mechanical Engineering Faculty, Thai Nguyen University of Technology, Vietnam
