Control of drop shape transformations in cooled emulsions

Area of Science:

• Materials Science
• Soft Matter Physics
• Chemical Engineering

Background:

• Morphogenesis, the generation of biological form, involves complex structure and shape transformations.
• Previous work demonstrated n-alkane drops in surfactant solutions self-shaping into geometric forms upon cooling.
• This self-shaping offers a bottom-up approach for complex particle production and a model for morphogenesis.

Purpose of the Study:

• To investigate if other chemical substances, beyond n-alkanes, exhibit spontaneous self-shaping into non-spherical forms.
• To identify the key factors influencing this drop self-shaping phenomenon.
• To classify surfactants based on their impact on self-shaping and propose explanations for observed trends.

Main Methods:

• Experimental study of drop self-shaping using various chemical substances including long-chain alcohols, triglycerides, alkyl cyclohexanes, and linear alkenes.
• Systematic variation of parameters: surfactant type and chain length, cooling rate, and initial drop size.
• Classification of surfactants into four groups based on their effect on self-shaping.

Main Results:

• Drops of alcohols, triglycerides, alkyl cyclohexanes, and alkenes spontaneously evolve into non-spherical shapes.
• Surfactant type, cooling rate, and initial drop size are identified as primary control factors for self-shaping.
• Surfactants are categorized into four distinct groups influencing the self-shaping process.

Conclusions:

• Simple chemical systems can exhibit complex shape transformations akin to biological morphogenesis.
• Molecular self-assembly under frustrated confinement drives these events via elasto-capillarity and tensegrity.
• Tailoring surfactant type and cooling rate allows for controlled production of micro-particles with specific shapes and aspect ratios.