Janus liquid marbles: Fabrication techniques, recent developments, and applications

Liquid marbles (LMs) are nonsticky droplets stabilized by hydrophobic solid particles that are adsorbed at the liquid–air interface. LMs are emerging as a potential platform in digital microfluidics, sensing applications, storage unit, biological incubation, and cosmetic applications. Incorporating multifunctional particles to form Janus liquid marble (JLM) could enhance the capabilities of the pristine LM. JLMs are multifunctional next-generation LMs comprising two hemispherical domains of distinct physicochemical properties such as size, hydrophobicity, electrical conductivity, surface functionalization, stimuli-responsivity, and so on. The JLMs offer precise control on the manipulability and enhanced performance over pristine LMs. Though the properties, applications, and progress of LMs are detailed in the recent literature, a focused review encompassing the fabrication, recent developments, potential applications of JLMs, and the challenges regarding its reliable fabrication remains a gap in the literature. The review provides insights into the importance of JLMs, systematically discussing the fabrication strategies, applications, challenges, and future directions.