Researchers at IIT Bombay, developed a new graphene-based Dual-Sided Superhydrophobic Laser-Induced Graphene (DSLIG) evaporator.

• This innovation offers a consistent, efficient, and scalable desalination solution by mimicking the lotus leaf effect, and integrating dual-mode heating (solar + electric).

Interfacial Solar Evaporation

• A method where only the surface layer of water is heated using a floating evaporator that absorbs sunlight. This avoids heating the full water volume, saving energy.

Advantage

• Localized heating: Ideal for off-grid desalination
• Higher thermal efficiency: Minimizes energy loss

Challenges with Solar Desalination Techniques

• Fluctuating Sunlight: Cloud cover and time-of-day variation cause unstable heating, lowering evaporation efficiency
• Low Absorption Efficiency: Reduced light absorption on some materials limits thermal performance
• Salt Deposition: Salt crystals accumulate on the evaporator surface, blocking water contact and reducing effectiveness.

About the DSLIG Evaporator Technology

• DSLIG = Dual-Sided Superhydrophobic Laser-Induced Graphene evaporator.
• Designed for interfacial solar desalination, enhanced with Joule heating backup.

Key Components

• PVDF (Polyvinylidene Fluoride): Provides superhydrophobicity (lotus-effect) on both sides.
• PES (Polyether Sulfone): Provides mechanical strength and flexibility.
• Laser-Induced Graphene (LIG): Engraved using laser to form graphene layer on PVDF for light absorption and heat conversion

Working Mechanism

• Solar heating: Heats a thin water layer at the surface for evaporation (localized heating).
• Electric heating: Joule heating compensates during cloudy conditions or low sunlight.
• Superhydrophobicity: Repels salt and water to prevent salt deposition on the surface.

Benefits of DSLIG Technology

Other Desalination Technologies

Desalination technologies are mainly categorized into two types based on the working principle:

A. Thermal Desalination Techniques

Definition: In thermal methods, saline water is heated and the resulting water vapor is condensed to produce freshwater. 

• These techniques mimic the natural water cycle and are best suited for seawater desalination, especially in regions with abundant thermal energy.

B. Membrane-Based Desalination Techniques

Definition: These methods use semi-permeable membranes to filter out dissolved salts and impurities from saline or brackish water by applying pressure or electric potential. 

• Preferred where electricity is available and chemical contamination is minimal.