Is the next major innovation in clean water technology perhaps the combination of two processing approaches that were thought to be mutually exclusive?
The scientists from Nanjing Tech University demonstrated that through the combination of 3D printing and frontal polymerization, the problems associated with soft and high-performance solar evaporators can actually be overcome. The process involved the mixture of a solution composed of Carbomer 940 and reactive vinyl monomers. Subsequently, the mixture was solidified in position through frontal polymerization. Another advantageous aspect of this process is that it is faster. This is because it depends on the self-propagating front of polymerization, which is required when frontal polymerization occurs.
This enabled the fabrication of an organogel evaporator with the ability to evaporate a rate of 3.77 kg m⁻² h⁻¹ under one sun at normal conditions, thus making it among the most effective evaporators for solar-based seawater desalination currently known. Compared to the evaporators fabricated using the carbonized biomass, most of them are yet to reach the values of 1.6 kg m⁻² h⁻¹, while the best hydrogel evaporators are yet to reach the values of 2 kg m⁻² h⁻¹. This is due to the resistive nature of the organ
Organogels having better attributes in a demanding situation than hydrogels have been discussed in current studies on gel-based materials. The freeze resistance, swelling resistance, or fouling resistance of frozen polymer networks swollen with organic solvents in the case of organogels assumes significance in the context of solar desalination, where the evaporators are subjected to high concentrations, temperature fluctuations, and fouling by biological agents. The combination of the attributes of organogel designs with the facilitations of 3D printing in the study by Nanjing Tech for enhanced rates of evaporation focuses on both requirements: enhanced durability and the need for microscopic details.
It leverages general improvements in solar desalination research, in which both matters are considered, in terms of materials and structure. Bionic and hierarchical structures seen in 3D-printed hydrogel evaporators featuring a tree-like structure for water channels have indicated how porosity control and directional water flow can be harnessed to suppress salt depositions and promote thermal localization. In a similar way, the organogel evaporator leverages both properties in which water flow paths help in fast replenishments to the evaporative interfaces, while its property of having low thermal conductivity prevents heat diffusion to the water bulk.
Aside from the desalination industry, the FTOP-based print technique also contains very attractive possible future uses in the area of soft robotics and the production of sustainable materials. Specifically in soft robotics, soft robots are now incorporating the use of gels and elastomers in their development of soft robot actuators, grippers, and shape-shifting components. As the latest advancements in soft robot actuators printed by 3D printing are introduced, it becomes apparent from the advancements in the field of soft robot replicas of biological motions that the development of complex structures that are position-dependent requires the use of the Nanjing Tech process to quickly produce said structures in an organogel system.
There is also a related field of soft robotics, where organogels or combinations of these and organohydrogels have already been used in efforts to minimize the swelling factor of the dielectric fluids used in electrohydrodynamic pumps, enabling the creation of soft robots that are not physically tied to the power source, assuming there is a high output pressure and a large flow rate. This can be even further possible by using the newly formed process of frontal polymerization. When considering manufacturing, the germination of polymers through the process of frontal polymerization consumes minimal amounts of energy. This is attributed to the fact that, as opposed to the case where the part is subjected to heating for a longer time in the process of thermal curing, the printed parts take only a couple of minutes to harden. For scientists studying the realm of renewable energy resources, the rate of desalination for the organogel evaporator holds significance not only for its rapid rate but perhaps even for its potentially long lifespan. The resistance against salt, the mechanisms, as well as the rate of heat conversion, for the reality of self-sufficiency-based solar desalination, have to be ensured. The robustness derived from the materials used, as well as the delicacy that architecture has to offer for this particular device, might just offer solutions for the development of a system that could potentially last weeks without undergoing degradation. It seems that this particular project offers insight into an even greater trend, namely the use of additive manufacturing techniques combined with polymer chemistry for the purpose of tackling the challenge of sustainability. With the capacity for fast curing cycles combined with the offers that 3D printing has within its realm, the group from Nanjing Tech has managed to offer what seems to be truly the start for what could potentially be considered a revolutionary technology. This has the capacity for being adapted for applications within water purification procedures at this moment, but has the possibilities for applications within soft robotics, bioscience, or infrastructure within the future.