Inspired by Nature: Janus Crystals and the Future of Water from Air

Atmospheric water harvesting technologies have been a focal point of innovation in addressing water scarcity. Current methods often utilize hydrophilic gels or absorbent materials to capture atmospheric moisture, while others depend on condensation systems. Many of these approaches, however, require energy inputs to complete the process of producing potable water—an enduring challenge that impacts millions of people worldwide. A novel strategy, inspired by organisms such as beetles and lizards that inhabit arid ecosystems, could revolutionize this process by achieving unprecedented efficiency without external energy.

This cutting-edge approach has been proposed by researchers at New York University, in collaboration with scientists from Abu Dhabi and China. The technology, named “Janus crystals,” operates without the need for external power sources and holds significant promise for sustainable water harvesting.

Current strategies for extracting water from the atmosphere​

Before delving into the specifics of Janus crystals, it is essential to review existing techniques for atmospheric water harvesting, especially in regions facing water scarcity, aridity, or drought. Atmospheric water generators (AWGs) typically employ one of the following strategies:

1. Passive condensation. This technique harnesses the temperature gradient between the air and a cooler surface to condense atmospheric moisture. Examples include fog-catching systems, which utilize specialized meshes to capture water droplets in arid regions with high fog density.
2. Active condensation. This method involves cooling air to its dew point using energy, causing water vapor to condense. Atmospheric water generators that mimic dehumidifiers are a key example of this approach.
3. Hygroscopic materials. These systems rely on materials such as silica gels or salt solutions that absorb water vapor directly from the air. The absorbed water is released by heating the materials, enabling water recovery.
4. Solar-based systems. Solar-powered technologies use sunlight to release water trapped in absorbent materials or to power condensation devices. These systems are particularly beneficial in remote areas due to their minimal reliance on external energy sources.
5. Advanced membranes for direct capture. These technologies incorporate membranes engineered with specific properties to trap and release water based on humidity levels. Examples include polymeric membranes and nanomaterials optimized for arid conditions.
6. Biomimetic technologies. Inspired by natural mechanisms, these systems replicate features observed in desert-dwelling organisms such as beetles and plants. Textures and surface chemistries are designed to enhance condensation and water collection efficiency.
7. Hybrid systems with renewable energies. These systems integrate active condensation methods with renewable energy sources, such as solar or wind, to enhance sustainability and minimize environmental impact.

​Janus crystals: inspired by desert organisms

The water harvesting system developed by researchers at New York University falls within the realm of biomimetic technologies. Inspired by strategies used by desert organisms, the system mimics the interplay of hydrophilic and hydrophobic surfaces, which are critical for trapping and transporting atmospheric water. Hydrophilic regions capture water vapor, while hydrophobic areas facilitate the movement of collected water.

The researchers, whose findings were published in the Journal of the American Chemical Society, created a novel type of elastic organic crystal. Among these, Janus crystals exhibit exceptional efficiency due to their unique structure, which combines hydrophilic and hydrophobic properties. This dual functionality allows the crystals to capture water vapor and direct it toward a collector with minimal energy loss.

Remarkably, Janus crystals operate without requiring external energy. Their translucent and narrow design also enables real-time visualization of water droplet formation and transport under light exposure.

By leveraging these properties, Janus crystals have the potential to serve as the basis for next-generation atmospheric water harvesting systems. These systems could complement existing innovations, such as fog-catching harps, while offering greater efficiency and scalability for water extraction in arid regions.

For additional insights into water treatment technologies with larger daily production capacities, consider exploring reverse osmosis desalination, which extracts freshwater from seawater. This approach continues to address pressing global water challenges.

Source:

• Science Daily