Zero-Energy Ultrafast Water Nanofiltration System in Microgravity

The goal of this program is to develop a water nanofiltration system that functions in microgravity for use during a long-duration human space exploration. The proposed nanofiltration system targets deep space crewed missions beyond low-Earth orbit (LEO) where it is impossible to launch fresh resupplies or carry sufficient mass and volume of life-sustaining equipment. Based on spontaneous surface-tension-driven flows, no external power is required to selectively transport water molecules through a nanostructured membrane. The speed of water transport through the membrane can be dramatically accelerated multiple orders of magnitude faster than prediction from conventional fluid-flow theory, while the confinement and electrostatic interactions lead to excellent salt rejection. The novelty of the microgravity filtration system includes zero-power consumption, ultrafast filtration, surface-tension-driven flow control in microgravity, excellent impurity rejection rate, lightweight, compact size, portability, recyclability and scalability. 

Current water filtration methods include distillation and membrane-based technologies. Both methods require a significant amount of energy. For example, reverse osmosis (RO), an energy-efficient membrane-based process, requires a fair amount of energy to apply 800-1000 psi across membrane filters. NASA tested a forward osmosis bag (FOB) on the ISS in an effort to provide a more energy-efficient solution. Despite lower power consumption (@ 25psi), the FOB required long filtration times (6 hours per 60 ml of a treated water sample), since it solely relies on a slow diffusion mechanism. Given limitations of energy and speed, a highly efficient filtration system is desperately needed for successful implementation of long-duration, deep space human exploration missions within the next 20 years. To achieve low power consumption and high speed, a new type of water filtration system is being researched on the basis of surface-tension-driven flows across a nanostructured membrane in microgravity.