Liquid metal enabled pump

Abstract

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 ...

Field‐Controlled Electrical Switch with Liquid Metal

“…This effect has been used to cause fluid motion through the so‐called continuous electrowetting and the Marangoni effect 34. Assuming that the LM droplet is equipotential (due to its high conductivity), there exists a variation of voltage across the drop due to the relatively low conductivity of the surrounding solution.…”

The pumping lid: investigating multi-material 3D printing for equipment-free, programmable generation of positive and negative pressures for microfluidic applications

“…The approaches described in this work address many of the fluid-handling challenges that are faced when working with microfluidic devices [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] including those involving laminar flow, 22,38 droplets, 21,[39][40][41] and cell culture experiments. [42][43][44] The simplicity of this pumping method overall and the use of the guiding structures make it robust to differences in pushing/pulling force; the user simply places a sample at the inlet and then pushes/pulls the pumping lid to generate the flow.…”

Liquid-Metal-Based Reconfigurable Components for RF Front Ends

“…The liquid metal can also be evacuated to turn the EBG element back on. A 1% solution of NaOH is used to reduce the oxide of Galinstan [39] and flush any residue when evacuating the channels. The channel is also lined with PTFE, which acts as a lubricant to facilitate pumping.…”