Electrochemically induced actuation of liquid metal marbles

Tang, Shi‐Yang; Sivan, V.; Khoshmanesh, Khashayar; O’Mullane, Anthony P.; Tang, Xinke; Gol, Berrak; Eshtiaghi, Nicky; Lieder, Felix; Petersen, Phred; Mitchell, Arnan; Kalantar‐zadeh, Kourosh

doi:10.1039/c3nr00185g

Cited by 221 publications

(213 citation statements)

References 35 publications

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“…We next observe that the coalesced drop shifts toward the grounded gate, which in this case is acting as the cathode (Figure 3b,c). This is, again, in contrast to what is typically seen in continuous electrowetting, during which EGaIn droplets in an NaOH solution move toward the anode 32, 33. Thus, we conclude that bipolar electrochemistry and oxidation must be the driving factor in our experiments.…”

Section: Resultsmentioning

confidence: 58%

Field‐Controlled Electrical Switch with Liquid Metal

2017

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When immersed in an electrolyte, droplets of Ga‐based liquid metal (LM) alloy can be manipulated in ways not possible with conventional electrocapillarity or electrowetting. This study demonstrates how LM electrochemistry can be exploited to coalesce and separate droplets under moderate voltages of ~1–10 V. This novel approach to droplet interaction can be explained with a theory that accounts for oxidation and reduction as well as fluidic instabilities. Based on simulations and experimental analysis, this study finds that droplet separation is governed by a unique limit‐point instability that arises from gradients in bipolar electrochemical reactions that lead to gradients in interfacial tension. The LM coalescence and separation are used to create a field‐programmable electrical switch. As with conventional relays or flip‐flop latch circuits, the system can transition between bistable (separated or coalesced) states, making it useful for memory storage, logic, and shape‐programmable circuitry using entirely liquids instead of solid‐state materials.

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Section: Resultsmentioning

confidence: 58%

Field‐Controlled Electrical Switch with Liquid Metal

2017

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“…1, the pressure difference Δp is positive, indicating that the downstream hemisphere of the droplet pushes the surrounding liquid harder and produces a force to drive the droplet toward the upstream (26). However, unlike (26), in this case, when the motion of the droplet is ceased by the neck of the chamber, the pressure difference across the droplet causes the flow of the surrounding liquid along the channel and thus converts the applied electric potential directly into mechanical movement of the liquid (detailed explanation is given in SI Appendix, section 2). Theoretically, the pressure difference exists continuously along the surface of the Galinstan droplet as long as the electric field is applied, and the principle for the resulting flow motion is called continuous electrowetting, which is an electrical analog to the Marangoni effect (4,26,27).…”

Section: Significancementioning

confidence: 99%

“…We also show that the system operates with other electrolytes, including neutral sodium chloride (NaCl) and Phosphate-buffered saline (PBS) solutions. However, the system does not operate with acidic electrolytes of pH less than 6.5, as we have previously demonstrated that Galinstan droplets in acidic solutions are weakly affected by electrowetting (26).…”

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confidence: 99%

“…In general, these liquid metals offer remarkable properties including high electrical conductivity (22), high density (22), high surface tension (22), extremely low vapor pressure (22), and low toxicity in comparison with their counterparts, such as mercury (22). These properties make them attractive for various applications such as in soft electronics (20,21), stretchable or makeshift components (20, 23), MEMS devices (24), and nanotechnology-enabled applications (25,26).…”

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confidence: 99%

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Liquid metal enabled pump

Tang¹,

Khoshmanesh²,

Sivan³

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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335

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Small-scale pumps will be the heartbeat of many future micro/ nanoscale platforms. However, the integration of small-scale pumps is presently hampered by limited flow rate with respect to the input power, and their rather complicated fabrication processes. These issues arise as many conventional pumping effects require intricate moving elements. Here, we demonstrate a system that we call the liquid metal enabled pump, for driving a range of liquids without mechanical moving parts, upon the application of modest electric field. This pump incorporates a droplet of liquid metal, which induces liquid flow at high flow rates, yet with exceptionally low power consumption by electrowetting/deelectrowetting at the metal surface. We present theory explaining this pumping mechanism and show that the operation is fundamentally different from other existing pumps. The presented liquid metal enabled pump is both efficient and simple, and thus has the potential to fundamentally advance the field of microfluidics.E ngines are systems that convert different kinds of energy into mechanical motion, which are used in various microscale systems, including laboratory-on-a-chip microreactors (1-3), microelectromechanical (MEMS) actuators (4), and microscale heat exchangers (5, 6), to name just a few. Some of the most important members of the engine family are liquid pumps. In the small-scale regime, such pumps can be mainly classified into mechanical and nonmechanical. For mechanical pumps, the driving force is generated by moving parts that are energized using piezoelectric (7), electrostatic (8), thermopneumatic (9), pneumatic (10), electromagnetic (11) effects, or deformation through electrowetting (12). Mechanical pumping systems have several drawbacks, which largely stem from the fact that moving parts cause energy loses due to heat generated by friction and their rather complicated fabrication processes (13,14). In addition, the existence of moving parts increases the potential for failure, which can become acute in complex systems and which could potentially include numerous pumps. Among the varieties of mechanical pumps, only piezoelectric units can produce high flow rates as large as 20,000 μL/min at relatively low input power (>50 mW) (13, 15). However, piezoelectric units generally require operating voltages larger than 100 V (13, 15). Alternatively, nonmechanical pumps with no moving parts generate a driving force using ions energized via electrohydrodynamic (16), electroosmotic (17), or electrochemical (18, 19) effects. However, ion pumps are generally only applicable for low-conductivity liquids, produce relatively low flow rates, and need very high voltages (in the order of kilovolts) to operate (13). Therefore, a pumping system with no moving parts, high flow rate, and low power consumption is ideal for many present-day and emerging applications in microfluidic systems. An ambitious vision is that such pumps can potentially be used for moving small objects on demand, assembling them to create new structures, or could ...

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“…Up to now, the search for safe‐handling room‐temperature LMs only narrows down to gallium‐based LMs, a group of alloys consisting gallium and other metals like indium, tin, etc. Recently, self‐powered motor,11 jumper,12 oscillator,13 soft actuators,14, 15, 16 and 2D semiconductor skin17 demonstrated with this class of material shed light on their new possibilities toward more diverse applications. Here, we report a particle‐eating phenomenon of gallium‐based LMs, which mimics the biological phagocytosis process (also known as cellular‐eating, a basic cell behavior referring to the transportation of external particles into cells from across the membranes18, 19, 20, 21), and thus we call it LM‐Phagocytosis.…”

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confidence: 99%

Liquid Metal Phagocytosis: Intermetallic Wetting Induced Particle Internalization

et al. 2017

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A biomimetic cellular‐eating phenomenon in gallium‐based liquid metal to realize particle internalization in full‐pH‐range solutions is reported. The effect, which is called liquid metal phagocytosis, represents a wet‐processing strategy to prepare various metallic liquid metal‐particle mixtures through introducing excitations such as an electrical polarization, a dissolving medium, or a sacrificial metal. A nonwetting‐to‐wetting transition resulting from surface transition and the reactive nature of the intermetallic wetting between the two metallic phases are found to be primarily responsible for such particle‐eating behavior. Theoretical study brings forward a physical picture to the problem, together with a generalized interpretation. The model developed here, which uses the macroscopic contact angle between the two metallic phases as a criterion to predict the particle internalization behavior, shows good consistency with experimental results.

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Electrochemically induced actuation of liquid metal marbles

Cited by 221 publications

References 35 publications

Field‐Controlled Electrical Switch with Liquid Metal

Field‐Controlled Electrical Switch with Liquid Metal

Liquid metal enabled pump

Liquid Metal Phagocytosis: Intermetallic Wetting Induced Particle Internalization

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