Crystals dancing to the tune of light will replace batteries

"We cut out the middle man, so to speak, and take light energy and turn it directly into mechanical deformation," explained Professor Ryan Hayward, James and Catherine Patten Endowed Professor of Chemical and Biological Engineering at the University of Colorado Boulder.

Unlike previous attempts with delicate crystalline solids that cracked when exposed to light, the team's approach involves using tiny organic crystals within a resilient polymer material. 

The crystals' unique orientation enables them to perform mechanical tasks such as bending or lifting objects when illuminated. This characteristic makes them not only versatile but also incredibly efficient. The material's capability to lift objects much heavier than itself hints at the potential for real-world applications.

Future Prospects and Challenges

By harnessing the power of light to generate mechanical work, the material could pave the way for self-powered robotic systems and drones that are no longer encumbered by heavy batteries.

"What's exciting is that these new actuators are much better than the ones we had before. They respond quickly, last a long time and can lift heavy things," the research team noted.

Looking forward, the researchers plan to fine-tune the material's responsiveness and efficiency. While the current state of the material allows it to transition from a flat to a curved state, the team aims to enhance its movement capabilities. 

"We still have a ways to go, particularly in terms of efficiency, before these materials can really compete with existing actuators. But this study is an important step in the right direction and gives us a roadmap for how we might be able to get there in the coming years," acknowledged Hayward, of the journey ahead. 

The research received support from beyond CU Boulder, including institutions such as the University of California Riverside and Stanford University. The project was funded by the Office of Naval Research, reflecting the widespread interest and potential applications of this groundbreaking technology.

As the world eagerly awaits further advancements in this field, the CU Boulder scientists' innovative material offers a glimpse into a future where light energy becomes the driving force behind efficient and wirelessly controlled mechanical systems. 

With the potential to reshape industries and power technologies of tomorrow, this breakthrough could soon lead us to a new era of energy-efficient innovation.

Study Abstract

Photomechanical crystals composed of three-dimensionally ordered and densely packed photochromes hold promise for high-performance photochemical actuators. However, bulk crystals with high structural ordering are severely limited in their flexibility, resulting in poor processibility and a tendency to fragment upon light exposure, while previous nano- or microcrystalline composites have lacked global alignment. Here we demonstrate a photon-fuelled macroscopic actuator consisting of diarylethene microcrystals in a polyethylene terephthalate host matrix. These microcrystals survive large deformations and show a high degree of three-dimensional ordering dictated by the anisotropic polyethylene terephthalate, which critically also has a similar stiffness. Overall, these ordered and compliant composites exhibit rapid response times, sustain a performance of over at least hundreds of cycles and generate work densities exceeding those of single crystals. Our composites represent the state-of-the-art for photochemical actuators and enable properties unattainable by single crystals, such as controllable, reversible and abrupt jumping (photosalient behaviour).