Hierarchical Optimization of High-Performance Biomimetic and Bioinspired Membranes

Abstract

Biomimetic and bioinspired membranes have emerged as an innovative platform for water purification and aqueous separations. They are inspired by the exceptional water permeability (∼109 water molecules per second per channel) and perfect selectivity of biological water channels, aquaporins. However, only few successes have been reported for channel-based membrane fabrication due to inherent challenges of realizing coherence between channel design at the angstrom level and development of scalable membranes that maintain these molecular properties at practice-relevant scales. In this article, we feature recent progress toward practical biomimetic membranes, with the review organized along a hierarchical structural perspective that biomimetic membranes commonly share. These structures range from unitary pore shapes and tubular hydrophobic channel geometries to self-assembled bilayer structures and finally to macroscale membranes covering a size range from the angstrom, to the micrometer scale, and finally to the centimeter and larger scales. To maximize the advantage of water channel implementation into membranes, each feature needs to be optimized in an appropriate manner that provides a path to successful scale-up to achieve high performance in practical biomimetic and bioinspired membranes.

Metal-coordinated sub-10 nm membranes for water purification

“…This indicates that the water diffusion across thicker skin layer becomes the rate-limiting step and can be activated by elevating temperature while the water diffusion across thinner skin layer is less sensitive to temperature. Furthermore, it is interesting to find that the E a value (9.56 kJ mol −1 ) of MOPM-Fe 3+ /PAN is about 60−70% lower than that of traditional polymeric membranes such as alginate polymer (31.29 kJ mol −1 ) 33 and polyamide (23.80 kJ mol −1 ) 34 , and even lower than that of graphene oxide membranes (11.12 kJ mol −1 ) 19 and aquaporin-incorporated polymeric membranes (AqpZ, 14.23 kJ mol −1 ) 4 which bear ultrafast water channels. The efficient water transport through the metal-organophosphate membrane is largely attributed to the sub-10 nm thickness and superhydrophilic nature of the MOPM-Fe 3+ layer.…”

“…The efficient water transport through the metal-organophosphate membrane is largely attributed to the sub-10 nm thickness and superhydrophilic nature of the MOPM-Fe 3+ layer. This backs up the conceptualized design of biomimetic water channel composed of hydrophilic entrance rims and low-resistance physical architecture 4 . As a result, the MOPM-Fe 3+ /PAN membranes exhibit unprecedented permeance in the range of 109.8−160.3 L m −2 h −1 bar −1 , remarkably higher than that of previously reported polymeric TFC and integrally asymmetric membranes with comparable dye rejections (Fig.…”

“…Since membrane permeation is inversely proportional to thickness, engineering ultrathin membranes with potentially high permeability and sufficient selectivity is critical to maximize membrane productivity and reduce membrane area 3 . As the basic building unit of living organisms, cell membrane sets a benchmark owing to the 7−8 nm thickness and exceptional permselectivity 4 . However, fabrication of sub-10 nm synthetic membranes which can simultaneously realize structural integrity and stability remains a grand challenge 5 .…”

Artificial water channels enable fast and selective water permeation through water-wire networks

“…As alternatives to biological water channels, bioinspired artificial water channels (AWCs) have rapidly emerged as a promising platform for next generation separation membranes 7,8 . AWCs are synthetic nanoarchitectures that mimic the function of AQPs.…”

Scattering versus fluorescence self-quenching: more than a question of faith for the quantification of water flux in large unilamellar vesicles?

“…Positively charged amino acids at the pore mouth potentially decrease the dehydration penalty of water molecules entering the single-file region and thereby enhance the passive water flow 20 . This knowledge is exquisitely important for the design of artificial channels [21][22][23][24][25][26][27] in material science, where the selectivity and permeability mechanism of AQPs serve as template to design artificial water channels envisioned to be used in next generation membrane-based separations and purifications. Similarly, AQPs [28][29][30][31][32][33][34][35] itself or carbon nanotubes 36 are envisioned as building blocks of biomimetic membranes.…”