Emulsions, i.e., mixtures of immiscible liquids, are the cornerstone of the personal care and cosmetics industries. In the form of hand lotions, shampoos, shaving creams, sunscreens and more, they enable a wide variety of ingredients to be quickly and conveniently delivered to hair and skin. However, despite their ubiquity, many possible ingredients experience significant changes in physical properties under high shear conditions, such as in traditional emulsification equipment. For example, many large molecules, both natural and synthetic, are non-Newtonian fluids. By definition, these fluids change their rheological properties under shear conditions. Examples include solutions of cornstarch and xanthan gum.
Traditionally, emulsions are formed under high shear conditions using static mixers, ultrasound devices, homogenizers or rotor/stator mixers but due to the limitations of these mixing technologies, compositions and processing conditions are typically over-designed to ensure product requirements are met. This results in the use, and often overuse, of chemical surfactants, the over-shearing sensitive materials, and high energy consumption. As an alternative, the authors propose the method of microchannel emulsification to enhance process control, thus enabling the introduction of new products to the market.
