What Is This Technology?
Researchers have developed a solar-powered sponge-like aerogel that can desalinate seawater using only sunlight and a simple plastic cover—no electricity required. This innovation, reported in ACS Energy Letters (2025), addresses a key challenge in sustainable desalination: scaling up the material without losing efficiency.
Unlike traditional desalination plants that consume vast amounts of energy, this system uses sunlight to evaporate water from seawater, leaving salt and impurities behind, then collects the purified water as it condenses on a plastic cover. The result is clean, drinkable water produced in an energy-free, low-cost, and scalable way.
How Does It Work?
1. Material Composition:
The core is a 3D-printed aerogel made from a paste containing carbon nanotubes and cellulose nanofibers. Carbon nanotubes efficiently absorb sunlight and convert it into heat, while cellulose nanofibers provide a lightweight, porous structure.
2. Structure and Printing:
The aerogel is printed layer by layer onto a frozen surface. This freeze-casting process creates a sponge-like material with vertical microscopic pores approximately 20 micrometers wide. These pores allow seawater to be drawn up by capillary action and facilitate efficient evaporation.
3. Evaporation Process:
When placed on seawater and covered with a transparent plastic dome, sunlight heats the aerogel’s surface. The heat evaporates the water inside the pores, but salt and other impurities remain in the seawater. The water vapor rises and condenses on the plastic cover.
4. Water Collection:
The condensed droplets run down the curved plastic cover and drip into a collection funnel and container, providing potable water.
5. Scalability:
A key breakthrough is that the evaporation rate remains consistent regardless of the aerogel’s size, solving a major limitation of previous materials where efficiency dropped as size increased.
Outdoor Test Results
In outdoor tests, a 3-inch-wide (8 cm) piece of the aerogel produced about 3 tablespoons (45 ml) of clean water in 6 hours of natural sunlight directly from seawater, demonstrating practical potential for small-scale, off-grid desalination.
Why Is This Important?
– Energy-free: Uses only sunlight, no electricity or fuel.
– Scalable: Maintains efficiency at larger sizes.
– Low-cost materials: Cellulose and carbon nanotubes are relatively affordable.
– Portable and simple: Could be used in remote or disaster-stricken areas lacking clean water infrastructure.
How Could You Make a Similar Solar-Powered Sponge for Desalination?
While replicating the exact 3D-printed aerogel requires specialized equipment and materials, here’s a simplified approach to build a basic solar desalination device inspired by this concept:
Materials Needed
– Porous sponge or aerogel substitute: A natural cellulose sponge or a commercially available aerogel panel.
– Black carbon-based paint or carbon nanotube ink: To coat the sponge and enhance solar absorption.
– Transparent plastic dome or cover: To trap evaporated water vapor.
– Container for seawater: A shallow basin or cup.
– Collection funnel and clean container: To collect condensed freshwater.
Step-by-Step Guide
1. Prepare the Sponge:
Coat the sponge with a thin layer of black carbon-based paint or carbon nanotube ink to improve sunlight absorption and heating. Let it dry completely.
2. Set Up the Device:
Place the sponge on top of the seawater container so it can wick water upwards via capillary action.
3. Cover with Plastic Dome:
Place a transparent plastic dome or cover over the setup, ensuring it’s sealed enough to trap water vapor but allows condensation on the inside surface.
4. Collect Condensate:
Position a funnel or channel so that condensed water droplets on the dome’s interior run down and drip into a clean container.
5. Place in Sunlight:
Set the device outdoors in direct sunlight. The sponge will heat up, evaporating water which condenses on the plastic and can be collected.
Limitations and Considerations
– This DIY version will be less efficient than the engineered aerogel.
– The sponge material may degrade over time due to salt exposure.
– Water output will be small, suitable for emergency or small-scale use.
– Proper cleaning and maintenance are essential to avoid contamination.
Summary
The solar-powered sponge aerogel developed by researchers represents a major step toward sustainable, energy-free desalination that could provide clean drinking water in off-grid and resource-limited settings. By combining advanced materials science (carbon nanotubes and cellulose nanofibers) with smart 3D printing, this technology maintains efficiency at practical sizes and harnesses sunlight to purify seawater.
While replicating the exact material requires specialized labs, simple solar stills inspired by this concept can be built using blackened sponges and plastic covers to harness solar evaporation and condensation at home or in emergencies.
References
– Shen, X. et al., “Scalable 3D-Printed Aerogels for Solar-Driven Seawater Desalination,” ACS Energy Letters, 2025, DOI: 10.1021/acsenergylett.5c01233
– American Chemical Society News, July 2025
– Review of solar desalination technologies, Renewable and Sustainable Energy Reviews, 2023
– Practical guides to solar still construction, Water Research Foundation, 2020