A research team led by Professor Wie Jeong-jae in Hanyang University’s Department of Organic Nano Engineering, together with Professor Kim Hak-rin (Kyungpook National University) and Professor Teng Zhang (Syracuse University, USA), announced a new design strategy that controls stiffness distribution to enhance jump performance and directional control.

‘Snap-through’ is a phenomenon seen in nature—like the Venus flytrap or small insects—where structures rapidly flip, creating fast, powerful movements. Recently, it has drawn attention as a biomimetic energy amplification technique, offering a way to unleash instantaneous force that surpasses the typical limitations in flexible materials.

Professor Wie’s team previously applied this snap-through mechanism to liquid crystal polymer network films, achieving light-driven jump motions. These films, which contain azobenzene groups, exhibit advantageous shape-changing and energy storage properties in response to ultraviolet stimulation. However, the system faced limitations, as it required adjustments in distribution of the external light to control jump directions, and challenges in maximizing jump performance due to the trade-off between retaining sufficient energy and effective bending based on material stiffness and flexibility.

To address these issues, the team proposed a novel “stiffness patterning design” that combines rigid and soft regions. Under UV light, soft zones bend easily and form an initial high curvature, while the stiff zones efficiently store elastic energy and then release it in an instant.

The team discovered that the film can provide varied jump patterns based on the location of stiff regions. Placing stiff areas at the film's edges enabled rotational and directional jumps, whereas stiff areas at the center resulted in vertical jumps of up to 49 mm (about 25 times the film's length). This happens because the soft areas keep curvature stable while the central stiff area delivers concentrated force to the surface for a powerful jump.

Furthermore, by increasing the film's aspect ratio and alternating the placement of soft and stiff zones in stripes, they enabled both vertical and directional control. This made it possible to switch jump types with a single film and achieve repeated actions, all without needing to change the direction of external light.

Professor Wie stated, “This research overcomes the inherent weakness of soft-material-based devices that struggle to generate force, marking a meaningful step for soft robotics. It can be applied in future small robotic systems needing efficient and powerful energy releases.”

The study was supported by the National Research Foundation of Korea (Mid-career Researcher Grant) and published in Science Advances, a leading international journal. The paper, Spatially Patterned Stiffness Variation in a Light-Triggered Jumper for Symmetry Breaking and High Snap-Through Efficiency, lists Ham Min-jung (Master-Doctorate integrated course student) as first author, Jo Woong-bi (Postdoctoral researcher) as co–first author, and Professor Wie Jeong-jae (Department of Organic Nano Engineering) as the corresponding author.