19.5.1 High-Energy Processes

These methods mainly involve mechanical energy in the form of pressure, wave, or

mechanical stirring. After disruption of coarse dispersion into very small droplets

and increasing the surface area, the process allows adsorption of surfactants at the

interface of and enables steric stabilization. The magnitude of mechanical energy

must be significantly greater than the interfacial energy so as to achieve a nano-range

of droplets. The following are the generally employed high-energy processes for the

fabrication of nanoemulsions.

19.5.1.1 High-Pressure Homogenization

The principle of nanoemulsification through high-pressure homogenization involves

passing the fluid through micro-orifice under positive pressure through the homoge-

nizer valve. In this process, shear, impact, and cavitation are the principal

mechanisms producing mechanical energy to disrupt the droplets into smaller size

(Shen 2012; Villalobos-Castillejos et al. 2018). The method involves mainly a two-

step process where in the first step, coarse droplets are reduced to ultrafine droplets

with an increased surface area. After size reduction to nano-range, the droplets tend

to undergo coalescence. Hence, the second step involves the role of the emulsifier

wherein the emulsifier adsorbs on the interface and reduces the interfacial tension.

An increase in emulsifier concentration and faster adsorption retard the coalescence

Table 19.1 (continued)

Oils

Surfactant/

cosurfactant

Concentration

Application

References

Tea tree oil

Polysorbate

80, isopropyl

myristate,

isopropyl

alcohol

Tea tree oil

(5%)

Anti-psoriatic

activity

Khokhra Sonia

(2011)

Fig. 19.1 Overview of method of preparation for nanoemulsions

19

Nanoemulsions: A Potential Advanced Nanocarrier Platform for Herbal Drug. . .

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