A Triple Bioinspired Surface Based on Perfluorodecyl Trimethoxysilane-Coated ZnO Nanosheets for Self-Driven Water Transport in a Flow Channel

Abstract

Water management is important for the bipolar plates of proton-exchange membrane fuel cells (PEMFCs), and active drainage is a desirable feature for the design of bipolar plate channels. Herein, inspired by natural micro-nanostructures, a triple bioinspired surface has been fabricated, which combines the advantages of both superhydrophobic and superhydrophilic surfaces. The superhydrophobic surface (FZnO@CA-GS) is prepared by PFTS (perfluorodecyl trimethoxysilance) coating on ZnO nanosheet-decorated arrays of microscale cylinders manufactured by photolithography, and second-round photolithography is used to convert the superhydrophobic surface into a surface with wedged superhydrophilic patterns (WSPs). Then, the water transport performance has been investigated for the WSP, where the square of the initial velocity of the droplet is found to be proportional to the wedge angle from both the theoretical calculation and experimental data. Subsequently, an index of the R value representing the flow state of droplets has been introduced to determine the optimal values for the geometrical parameters of triple-bioinspired surface (TBS) in flow channels. Such a triple bioinspired strategy affords a promising approach to fabricate bipolar plate channels with the function of self-driven water transport for PEMFC. The use of the R value in optimization may also offer insights into the design of other micro-nanostructures.

A nature-inspired solution for water management in flow fields for electrochemical devices

“…50,68 Only the hydrophilic surface of the integument of the desert beetle constitutes the source of inspiration and a hydrophilic coating is applied within the channels of a conventional flow-field; the network of micro-sized grooves that transports the water from its integument to its mouth is not considered. 50,68 As a result, water removal from such bioimitating flow-fields still relies on pressure drop (gas transport) with questionable stability, reproducibility, and scalability, as, at larger scales, pressure drop within the flow-field significantly increases, thus enhancing parasitic energy losses. 31 In our work, a thin graphite plate with laser-engraved microchannel structure is engineered via a compact laser micromachining system and installed in a commercial flowfield (serpentine and parallel) and our best performing lunginspired flow-field (N = 4) based PEMFCs.…”

“…This is demonstrated in recent reports mimicking the water drinking mechanism of certain desert beetles, which bears similarities to the one of lizards living in arid environments, to improve the water management within a PEMFC. 50,68 Only the hydrophilic surface of the integument of the desert beetle constitutes the source of inspiration and a hydrophilic coating is applied within the channels of a conventional flow-field; the network of micro-sized grooves that transports the water from its integument to its mouth is not considered. 50,68 As a result, water removal from such bio-imitating flow-fields still relies on pressure drop (gas transport) with questionable stability, reproducibility, and scalability, as, at larger scales, pressure drop within the flow-field significantly increases, thus enhancing parasitic energy losses.…”

Graphene Oxide Nanopowder-Based Hydrophobic Fluid Diode Fabric with Passive Radiative Warming for Simultaneous Thermal and Moisture Management during Cold Weather

“…The other way is to reduce the sweat residue on both the skin and the fabric, thereby reducing the amount of heat lost by evaporation. To reduce the sweat residue on the skin, materials with directional moisture transport properties (namely, fluid diodes) that combine hydrophilic and hydrophobic sections (Janus materials), as well as all-hydrophilic materials, have been proposed and implemented to transfer sweat from the skin side to the outer side of the fabric. − These materials can provide a degree of dryness to the individual, but sweat is still present at the hydrophilic layer and evaporation of the residual sweat consumes body heat, which decreases the warming capability of the fabric. , Few studies have reported sweat residue reduction in both the skin and the fabric. Unlike a liquid diode with a hydrophilic layer, a new kind of liquid diode fabric made entirely of all-hydrophobic materials was previously reported by the authors .…”

A Review on Fabrication and Application of Tunable Hybrid Micro–Nano Array Surfaces

“…[12] Therefore, modulation of surface wettability or directional transport of droplets can be achieved by controlling the interaction between the micro-nanosurface structure and droplets. For example, under external stimuli such as force, temperature, humidity, pH, light, electricity, and magnetism, the wettability [13] and adhesion [14] of the material surface change, which can achieve hydrophilic and hydrophobic conversion, [15] droplet/microfluidic transport, [16] and surface adhesion adjustment. [17] In addition to the wettability, the surface micro-nano array structure can also be converted into detectable electrical signals under external stimulation, which can decode the information carried by the feedback.…”