Scientists have developed a new type of soft robot that can move and change shape in response to sunlight, without the need for batteries or external control. The robots are made of liquid crystal elastomers (LCEs), which are materials that can undergo large deformations when exposed to light, heat, or electric fields.
The researchers, led by Ximin He from the University of California, Los Angeles, designed the LCEs to have a bilayer structure, where one layer is more responsive to light than the other. This creates a bending motion when the LCE is illuminated, similar to how a bimetallic strip bends when heated. By carefully tuning the properties of the LCEs, such as the thickness, modulus, and photothermal conversion, the researchers were able to achieve self-excited oscillation, where the LCE bends and unbends repeatedly under a constant light source. This is different from previous light-responsive soft robots, which usually require a periodic or modulated light input to generate oscillatory motion.
The self-excited oscillation of the LCEs can be used to power various types of soft robots, such as a sailboat, a walker, a roller, and synchronized flapping wings. The researchers demonstrated that these robots can move autonomously and sustainably under one-Sun illumination, which is the average intensity of sunlight on Earth. The robots can also adjust their motion according to the direction and intensity of the light source, showing a form of environmental adaptation and intelligence.
Advantages and challenges of sunlight-powered soft robotics
The sunlight-powered soft robots have several advantages over conventional soft robots, which usually rely on batteries, wires, or pneumatic systems to operate. The sunlight-powered robots are more lightweight, flexible, and environmentally friendly, as they can harvest renewable energy from the surroundings and do not produce any waste or emissions. The robots are also fully untethered and do not need any external control or programming, making them suitable for applications in remote or inaccessible areas, such as space exploration, environmental monitoring, or disaster relief.
However, the sunlight-powered soft robots also face some challenges and limitations, such as the dependence on the availability and quality of sunlight, the low efficiency and durability of the LCEs, and the lack of sophisticated sensing and feedback mechanisms. The researchers suggest that future work could address these issues by improving the design and fabrication of the LCEs, integrating other stimuli-responsive materials and components, and developing more complex and adaptive behaviors and functions for the robots.
A new paradigm for soft robotics
The sunlight-powered soft robots represent a new paradigm for soft robotics, where the energy supply and motion control are both achieved by exploiting the inherent properties and interactions of the materials. This approach simplifies the design and operation of the robots, while also enhancing their autonomy and sustainability. The researchers hope that their work could inspire more research and innovation in the field of soft robotics, and lead to the development of novel and useful applications for society.