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(Upper) SEM micrographs of fumed silica particle powder containing a 100%, b 61%, c 50%, d 33% and e 14% residual SiOH groups and f Aerosil R202 powder. (Lower) SEM micrographs of: a raw hydrophilic (PF-0) and b PF-5, c PF-8, and b PF-12 fluorinated sericite clay particles
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Conventional qualitative analysis of ions from inorganic salts and acid–base and redox titrations require relatively large volumes of solution and hence require more reagent and generate relatively large amount of waste. Liquid marbles can be used to cut down the volume of solution and by extension the amount of reagent and volume of waste generate...
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Gas–liquid–liquid three-phase flow systems have unique advantages of controlling reagent manipulation and improving reaction performance. However, there remains a lack of insight into the dynamics and controllability of water droplet fusion assisted by gas bubbles, particularly scaling laws for use in the design and operation of complex multiphase...
Citations
... Both liquid computers and living organisms need chemical energy to operate. They use non-electric inputs and CO 2 is one of waste products of information processing [6]. Nature-made liquid computers, like for example the Human brain, seem to be highly optimized for energy consumption. ...
Our study is focused on identification of the best medium for future experiments on information processing with Belousov–Zhabotinsky reaction proceeding in Dowex beads with immobilized catalyst inside. The optimum medium should be characterized by long and stable nonlinear behavior, mechanical stability and should allow for control with electric potential. We considered different types of Dowex ion-exchange resins, bead distributions and various initial concentrations of substrates: malonic acid and 1,4-cyclohexanedione. The electric potential on platinum electrodes, stabilized by a potentiostat is used to control medium evolution. A negative electric potential generates activator species HBrO2 on the working electrode according to the reaction: BrO3− + 2e− + 3H+ → HBrO2 + H2O, while positive electric potential attracts inhibitor species Br− to the proximity of it. We study oscillation amplitude and period stability in systems with ferroin loaded Dowex 50W-X2 and Dowex 50W-X8 beads during experiments exceeding 16 h. It has been observed, that the above mentioned resins generate a smaller number of CO2 bubbles close to the beads than Dowex 50W-X4, which makes Dowex 50W-X2 and Dowex 50W-X8 more suitable for applications in chemical computing. We report amplitude stability, oscillation frequency, merging and annihilation of travelling waves in a lattice of Dowex 50W-X8 beads (mesh size 50–100) in over 19 h long experiments with equimolar solution of malonic acid and 1,4-cyclohexanedione. This system looks as a promising candidate for chemical computing devices that can operate for a day.
... Core-shell beads made with composite liquid marbles were implemented as a microreactor for polymerase chain reactions [16]. Liquid marbles were successfully used for qualitative analysis of ions from inorganic salt solutions and acid-base and redox titrations [17]. In our recent research, we introduced the composite (sandwich) liquid marbles, i.e. bi-liquid droplets, prepared with water droplets coated by a thin silicone oil layer containing hydrophobic, colloidal particles [18,19]. ...
Abstract Hypothesis We hypothesized that the reported evolution (growth) of composite water marbles filled with saline water and coated with lycopodium dispersed in a thin layer of silicone oil is due to the osmotic mass transfer. The hypothesis is supported by the semi-empirical model of osmotic growth of small liquid marbles floating on distilled water. Experiments Saline composite, silicone oil-coated marbles floating on distilled water grew with time; whereas, composite marbles filled with distilled water floating on aqueous solutions of NaCl lost mass with time and shrunk. However, composite liquid marbles filled with saline water and floating on aqueous solutions of NaCl remained stable during 25 hours of the laboratory experiment. Findings The reported findings are reasonably attributed to osmotic mass transport through the thin silicon layer filled with lycopodium particles coating the marbles, acting as an osmotic membrane. This is supported by the suggested model for the osmotic growth of marbles. Keywords: liquid marbles, osmotic mass transfer, osmotic membrane; floating; lycopodium
... We conclude that liquid marbles [1][2][3][4][5][6][7][8][9][10] immersed into the crosslinked PDMS matrix enable the soft lithography process [27], namely allow the formation of near-surface cavities, decorated with the toroidal residues, built of the colloidal particles, initially coating the marble. Water liquid marbles coated with lycopodium, polyethylene, and polytetrafluoroethylene particles did not sink when introduced into the PDMS matrix.Still, they remained attached to the PDMS/air interface from below due to the capillary bridges, supporting the marbles. ...
The soft lithography process with water marbles immersed into the PDMS matrix is demonstrated. Near-surface cavities, decorated with the toroidal residues, built of the colloidal particles, initially coating the marbles, are formed in the course of evaporation of water filling the liquid marbles. Water liquid marbles coated with lycopodium, polyethylene and polytetrafluoroethylene particles remained attached to the PDMS/air interface from below due to the capillary bridges. The analysis of the equilibrium of a liquid marble supported by the capillary bridge is suggested. Thermal fields arising from cross-linking of PDMS and evaporation of water from liquid marbles are explored. The migration of colloidal particles coating the marbles towards the contact line in the course of water evaporation is reported and analyzed. Migration of particles is related to the “coffee-stain effect”. Mechanical properties of the PDMS samples stamped with the liquid marbles are reported.
... The formation rate of the violet colour from the reaction of glucose and its detection reagent was measured to determine the correlation coefficient between the reaction rate and glucose concentration. By using liquid marbles containing test reagents, Tyowua et al. were able to identify cations and anions, as well as conduct acid-base and redox titrations without introducing any external actuation fields [77]. These tests were done simply by merging droplets of test reagents with liquid marbles and observing the colour change of the indicators. ...
The need for miniaturised reaction systems has led to the development of various microreactor platforms, such as droplet-based microreactors. However, these microreactors possess inherent drawbacks, such as rapid evaporation and difficult handling, that limit their use in practical applications. Liquid marbles are droplets covered with hydrophobic particles and are a potential platform that can overcome the weaknesses of bare droplets. The coating particles completely isolate the interior liquids from the surrounding environment, thus conveniently encapsulating the reactions. Great efforts have been made over the past decade to demonstrate the feasibility of liquid marble-based microreactors for chemical and biological applications. This review systemically summarises state-of-the-art implementations of liquid marbles as microreactors. This paper also discusses the various aspects of liquid marble-based microreactors, such as the formation, manipulation, and future perspectives.
Liquid marbles have the potential for microfluidic transport, medical diagnostics, and chemical analysis due to their negligible stickiness, environmental independence, and excellent mobility. Here, we report a non-contact manipulation strategy to arouse a reciprocating oscillation of ferrofluid marbles floating on the water surface, which can be used as microreactors. We experimentally investigated the quantitative relationship between the oscillation behavior, the applied magnetic field parameters, and the field regulation mechanism. The variables, including the magnetic field strength, marble volume, and switching period, are vital in determining the final state. The oscillation can be separated into three stages: transitional movement, compressive deformation, and rebound, before entering the next cycle. Accordingly, we created a manipulation technique for improving the mixing of inner reactants inside this marble container by remote-controlled shaking after optimizing with an oscillation model.
Liquid marbles allow for quantities of various liquids to be encapsulated by hydrophobic particles, thus ensuring isolation from the external environment. The unique properties provided by this soft solid has allowed for use in a wide array of different applications. Liquid marbles do however have certain drawbacks, with lifetime and robustness often being limited. Within this review, particle characteristics that impact liquid marble stability are critically discussed, in addition to other factors, such as internal and external environments, that can be engineered to achieve a robust long‐lived liquid marble. New emerging applications, which will benefit from this improvement, are explored such as unconventional computing, cell mimicry, and soft lithography. Incorporation of liquid marbles and liquid crystal technologies shows promise in utilizing structural color for optical display applications, and within green and environmental applications, liquid marble technology is increasingly adapted for use in energy conversion, heavy metal recovery, CO2 capture, and oil removal. Liquid marbles offer unique and desirable properties for numerous applications. This review focuses on their more recent incorporation within green applications, such as carbon dioxide and oil capture. It considers how their lifetime and robustness can be improved to be better suited to real life functions, to ensure a more long‐lived and useful device.
Abstract
Hypothesis
We hypothesized that the reported evolution (growth) of composite water marbles filled with saline water and coated with lycopodium dispersed in a thin layer of silicone oil is due to the osmotic mass transfer. The hypothesis is supported by the semi-empirical model of osmotic growth of small liquid marbles floating on distilled water.
Experiments
Saline composite, silicone oil-coated marbles floating on distilled water grew with time; whereas, composite marbles filled with distilled water floating on aqueous solutions of NaCl lost mass with time and shrunk. However, composite liquid marbles filled with saline water and floating on aqueous solutions of NaCl remained stable during 25 hours of the laboratory experiment.
Findings
The reported findings are reasonably attributed to osmotic mass transport through the thin silicon layer filled with lycopodium particles coating the marbles, acting as an osmotic membrane. This is supported by the suggested model for the osmotic growth of marbles.
Keywords: liquid marbles, osmotic mass transfer, osmotic membrane; floating; lycopodium
Liquid marbles are droplets with volume typically on the order of microliters coated with hydrophobic powder. The versatility, ease of use and low cost make liquid marbles an attractive platform for digital microfluidics. This paper provides the state of the art of discoveries in the physics of liquid marbles and their practical applications. The paper first discusses the fundamental properties of liquid marbles, followed by the sumary of diferent technqies for the synthesis of liquid marbles. Next, manipulation technqiues for handling liquid marbles are discussed. Applications of liquid marbles are categorised according to their use as chemical and bological reactors. The paper concludes with perspectives on the future development of liquid marble based digital microfluidics.
