Manipulation schemes and applications of liquid marbles for micro total analysis systems

Abstract

Micro total analysis systems (microTAS) provide the opportunity to create complete analytical microsystems by integrating various functional modules, such as sample preparation, separation and detection, into a single chipsized microfabricated device. Microfluidics is the enabling technology for implementing the concept of microTAS. Liquid marble (LM), as a promising separate digital microfluidic platform, has the great potential to enhance the broad applications of microTAS. LMs are small liquid droplets encapsulated by multilayered hydrophobic particles and have attracted a great interest from the microfluidics research community due to their non-wetting property. A LM maintains its integrity and exhibits low friction on various carrier surfaces, enabling the LM to be actuated by external electric, magnetic, gravitational and acoustic fields or other manipulation schemes. LMs can thus serve effectively for the storage and transportation of small liquid volumes. In addition, they have been widely used for the quick detection of water pollution or gas emission and, most importantly, micromixing and microreactions for chemical and biomedical purposes. This paper reviews the recent developments in the manipulation techniques and emerging applications of LMs. The review aims to facilitate better understanding of their use as a unique digital microfluidic platform to promote further advancement of microTAS. The paper begins with different manipulation schemes of LMs according to the nature of actuation energy. Next, it summarises the diverse applications of LMs for various chemical and biological assays. Finally, this paper concludes with future perspectives regarding the research on LMs in microTAS technologies.

Critical Trapping Conditions for Floating Liquid Marbles

“…They can stably rest or float on different solid and liquid substrates and even move across these surfaces with low loss, no leakage and relatively low evaporation [7][8][9][10][11][12]. These features make LMs the better alternative than droplets on a superhydrophobic surface for the storage and transport of a small amount of liquid [13,14]. LMs floating on a carrier liquid can maintain their volumes for a long period of time.…”

Dielectrophoretic Trapping of a Floating Liquid Marble

“…Compared to bare droplets on a superhydrophobic surface, LMs provide a promising alternative to the transport and storage of small liquid volumes. LMs can move across different solid or liquid surfaces with a relatively small initial force, practically zero contamination, good compressive capability, a slower evaporation rate, and consequently less mass loss [4][5][6][7][8]. This feature is attributed to the presence of the protective porous particle shell around the liquid core as well as the air cushions between the LM and the carrier surface [5,9].…”

“…LMs can move across different solid or liquid surfaces with a relatively small initial force, practically zero contamination, good compressive capability, a slower evaporation rate, and consequently less mass loss [4][5][6][7][8]. This feature is attributed to the presence of the protective porous particle shell around the liquid core as well as the air cushions between the LM and the carrier surface [5,9]. Unlike the complicated and costly electrowetting-based digital microfluidics (DMF), LM-based DMF relies on manipulating discrete droplets without being confined in a closed channel or the need for an insulating hydrophobic surface.…”

Biosensors-on-Chip: An Up-to-Date Review

“…BoC systems are based on micro-total analysis systems, which aim to provide complete analytical microscaled systems by diminishing and accumulating all steps required for sample analysis within a single device [ 26 , 38 ]. Specifically, it must allow the performance of standard laboratory functions, including sample injection, mixing, reaction, separation, and enrichment, and analyte detection [ 26 , 38 , 39 , 40 ]. Therefore, such systems may contain a variety of units, and their design is generally not straightforward [ 41 , 42 ], as they can function based on passive, active, or hybrid mechanisms.…”