Low‐voltage efficient electroosmotic pumps with ultrathin silica nanoporous membrane

Abstract

In this work, an efficient electroosmotic pump (EOP) based on the ultrathin silica nanoporous membrane (u‐SNM), which can drive the motion of fluid under the operating voltage as low as 0.2 V, has been fabricated. Thanks to the ultrathin thickness of u‐SNM (∼75 nm), the effective electric field strength across u‐SNM could be as high as 8.27 × 105 V m−1 in 0.4 M KCl when 1.0 V of voltage was applied. The maximum normalized electroosmotic flow (EOF) rate was as high as 172.90 mL/min/cm2/V, which was larger than most of other nanoporous membrane based EOPs. In addition to the ultrathin thickness, the high porosity of this membrane (with a pore density of 4 × 1012 cm−2, corresponding to a porosity of 16.7%) also contribute to such a high EOF rate. Moreover, the EOF rate was found to be proportional to both the applied voltage and the electrolyte concentration. Because of small electrokinetic radius of u‐SNM arising from its ultrasmall pore size (ca. 2.3 nm in diameter), the EOF rate increased with increasing the electrolyte concentration and reached the maximum at a concentration of 0.4 M. This dependence was rationalized by the variations of both zeta potential and electrokinetic radius with the electrolyte concentration.

Rational ion transport management mediated through membrane structures

“…Polyamide, [213,214,270] CMF, [158,159] O/O (e.g., PC/CP [105][106] and hydrogel/CP [82] ), and O/I heterogeneous membranes (e.g., CP/AAO [184,185,201] ) are usually obtained by an interfacial polymerization method. Other methods such as mechanical shearing, Stöber solution growth, and micelle templates have been used to construct MXenes with a vertical arrangement, [40] SiO 2 with perpendicular nanochannels, [59,188,218,219,271] and CPs with ordered mesopores, [231,272,273] respectively.…”

“…Stöber solution growth SiO 2 with perpendicular nanochannels [59,188,218,219,271] [ 59,188,218,219,271] Micelle template CPs with ordered mesopores [231,272,273] [ 231,272,273] F I G U R E   Applications of membranes with unique structures. (A) Ion transport through MOFs (left) and ion conductance of different electrolyte solutions with and without MOFs (right).…”

Regulating the aggregation of colloidal particles in an electro-osmotic micropump

“…EOP-based nanoporous membranes have been applied in various methods of analytical and physical chemistry, such as: liquidchromatography separation, 13 use of femto-liter pipettes, 14 micro-energy systems, 15 and micro-nanofluidic microchips. 16 A common challenge facing the field is that in many situations involving EOPs, there is a tendency for the microfluidic device to become clogged with aggregates of CPs. This limits the effectiveness of these setups and their durability, and presents a major obstacle to their technological application.…”

“…The reason for this is that in EOPs the average flow velocity is independent of the channel diameter 11,12 , unlike pressure-driven flow, where the average flow velocity decreases with the square of the channel diameter. EOP-based nanoporous membranes have been applied in various methods of analyti-cal and physical chemistry, such as: liquid-chromatography separation 13 , femto-liter pipettes 14 , micro-energy systems 15 , and micro-nanofluidic microchips 16 . A common challenge facing the field is that in many situations involving EOPs, there is a tendency for the microfluidic device to become clogged with aggregates of CPs.…”

Electro-Osmotic Behavior of Polymeric Cation-Exchange Membranes in Ethanol-Water Solutions

“…Electrokinetic effects in membrane systems can be utilized for conversion between mechanical and electrical energies [ 4 , 5 , 6 , 7 , 8 , 9 , 10 ]. These systems could also be used as electric generators or electrokinetic pumps [ 11 , 12 , 13 ], and the efficiency of the process strongly depends on the membranes’ properties. Due to their potential applications, they have increasingly attracted more and more attention.…”