A recent article in Advanced Materials reports the development of a three-dimensional (3D) printed auxetic, self-powered, mechanoluminescent (ML) photonic skin designed for underwater communication and safety monitoring.
The material emits light in response to mechanical stimuli and conforms to curved surfaces without requiring an external power source. The objective was to improve visibility and durability in underwater environments through a flexible, energy-efficient approach.
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Underwater Communication Technology
Exploration of deep-sea environments is limited by extreme conditions. Conventional underwater lighting systems, such as LEDs and optical fibers, can be constrained by reliance on external power and limited adaptability to irregular or dynamic surfaces. Mechanoluminescence, the emission of light in response to mechanical stress, offers a method for visualizing mechanical events without external energy sources.
Auxetic materials, which have a negative Poisson’s ratio and expand laterally when stretched, can improve flexibility and surface conformity in ML-based devices. By combining ML materials with auxetic structures, researchers aim to develop photonic skins that are mechanically stable under deformation.
Design and Fabrication of the Photonic Skin
The photonic skin was produced using a composite of zinc sulfide (ZnS), copper (Cu), and silicone. ZnS-based phosphor microparticles were chosen for their chemical stability and compatibility with underwater use. The device was fabricated using direct ink writing (DIW), a 3D printing method suitable for creating structured auxetic patterns.
To formulate the ML ink, polydimethylsiloxane (PDMS) and Ecoflex silicone were blended with ZnS-based phosphor particles. This composite was extruded through a nozzle to form periodic structures.
Rheological testing confirmed the ink's shear-thinning behavior, which allowed for smooth extrusion and shape retention. Finite Element Analysis (FEA) simulations assessed the printed structures’ ability to conform to various curved surfaces.
Key Findings and Performance Metrics
The photonic skin retained mechanical and optical performance over more than 10,000 cycles of stretching and releasing. The study examined the relationship between ML brightness and stretchability: increasing phosphor content enhanced light emission but reduced the strain range. Encapsulation with a transparent silicone layer increased the device’s stretchability from about 11 % to over 90 %, while maintaining structural stability.
Peak ML brightness reached 7.4 cd m⁻² at 10 % strain, and the device continued functioning at higher strain levels. FEA simulations confirmed that the auxetic structures adapted well to both singly and doubly curved surfaces.
A video-based method was introduced to measure ML brightness during stretching. Practical applications were demonstrated by incorporating the photonic skin into wearable devices, such as gloves, to enable underwater Morse code communication via finger motion. The material also responded to gas leakage by emitting light at defect sites, enabling real-time visual detection.
Applications in Marine Monitoring and Robotics
The self-powered photonic skin may be used in underwater robotics, diver signaling, and marine communication systems. Its ability to function without batteries supports long-term use in environments where electronic components may be limited.
Mechanical sensitivity allows for early detection of stress or damage, such as gas leaks, which is useful for monitoring equipment like pipelines and tanks.
In low-visibility underwater settings, mechanical activation of light emission enables electronic-free signaling, which may be beneficial for divers. The material’s stability in saline and varying temperature conditions, along with its ability to emit different colors, supports its use in various underwater sensing tasks.
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Future Outlook
The study presents a method for creating auxetic, self-powered ML photonic skins using 3D printing. The resulting device is flexible, light-responsive, and suitable for underwater operation without external power sources.
After extended use, the device maintained approximately 70 % of its initial brightness and demonstrated resistance to environmental stressors such as salinity and temperature shifts.
This material provides a non-electronic approach to visual signaling and monitoring in underwater environments. Its integration into wearable and soft robotic systems highlights its potential utility in marine safety, environmental monitoring, and related applications.
Future work may extend its use to additional domains, such as environmental sensing and aerospace.
Journal Reference
Sun, X., et al. (2025). 3D Printing of Auxetic Self-powered Mechanoluminescent Photonic Skins for Underwater Communication and Safety Monitoring. Advanced Materials. 10.1002/adma.202502743, https://advanced.onlinelibrary.wiley.com/doi/10.1002/adma.202502743
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