Our world is dominated by intricate machinery and complex designs, but sometimes it’s the simplest tools that have the potential to revolutionize how we interact with the world. In our latest research venture, we bring together the humble ink pen and paper origami, not for art, but for a purpose that nudges the boundaries of technological innovation - creating a Marangoni swimmer capable of intricate programmable motions.

Image 1. The Art of Propulsion: A Pen-Drawing Process Breathing Life into Marangoni Swimmers

The basis of our technology is an ink pen filled with camphor. When the ink interacts with water, it generates forces that propel the swimmer across the water surface, guided by the intricate patterns drawn on it. The concept is simple, but the implications are groundbreaking.

With our pen-drawn approach, we’re not just creating a swimmer that can move. We're opening up a world of potential for programmable micro-robots. Our technology is as versatile as it is simple. By altering the substrate, fuel composition, and spatial engine pattern, we can program complex motions and even perform advanced tasks. Beyond the pen-drawn propulsion, we've introduced another level of complexity - an origami-inspired structure. The flexibility of origami allows the swimmer to change its structure over time, creating the potential for multi-step motions. Despite its simple form, our origami swimmer can morph and adapt to perform tasks typically associated with more complex robotics. This origami approach allows for a higher degree of adjustability, a factor that could revolutionize how we think about robotic mobility and function. Additionally, we implemented disassembly of a single swimmer into two separate entities using a water-soluble pullulan film bridge. When this film dissolves upon contact with water, the swimmers separate, each following its individual motion program based on its engine design and shape. We have demonstrated a swimmer capable of multistep motion, cargo delivery, and self-recovery in an inlet-only environment. These features expand the potential of miniaturized autonomous robots, especially in areas with restricted human access. Also, the dynamic engine designs could inspire future research into Marangoni swimmers with greater motion programmability. The beauty lies in how our simple origami swimmer morphs and adjusts itself to perform complex tasks, blurring the line between simplicity and complexity.

However, we recognize the challenges ahead. Manual drawing may limit the accuracy and reproducibility of our swimmer's motions, and miniaturizing the technology to a micro-robotic scale remains a significant hurdle. Yet, the benefits outweigh these concerns. The ink-based printing method allows easy processing of different fuel ink concentrations on the same substrate, enabling advanced motion programmability. Moreover, it is compatible with conventional 2D printing technologies, such as pen-plotter and inkjet printing.

Looking ahead, we foresee the integration of computer-aided design (CAD) and automated printing as crucial for more accurate, miniaturized, and mass-producible fabrications. The use of non-toxic materials makes our approach particularly suitable for educational purposes. Even without specific expertise, the general public and students can explore Marangoni propulsion robots as part of the STEM (Science, Technology, Engineering, & Mathematics).

By leveraging the humble ink pen and origami paper, we've opened new frontiers in the field of robotics. We’re not only excited about the potential of our work but also about its ability to inspire future innovations that continue to blur the line between simplicity and complexity. The act has just begun, and we're thrilled about the journey ahead, ready to embrace the challenges and opportunities that it brings.