Pukyong National University

Pukyong National University Researchers Develop Light-Activated Microneedle Soft Robot for Remote Injection in Future Smart Livestock Farming

- Professor Dae-Seok Kim’s Team Publishes Findings in the International Materials Chemistry Journal Advanced Functional Materials

A joint research team at Pukyong National University has developed a new soft actuator technology that generates a rapid, powerful force from a light-responsive soft material to insert microneedles into the skin.

The research team, led by Professor Dae-Seok Kim and master’s student Chae-Won Lee of the Major of Polymer Engineering, together with Professor Seung-Hyun Park and integrated master’s and doctoral student Nan-Kyung Kim of the Major of Human Bio-Convergence, successfully developed a high-output remote microneedle actuation system that combines a light-responsive liquid crystal elastomer (LCE), magnets, and a snap-through structure.

Liquid crystal elastomers are soft and flexible like rubber yet can change their shape in response to external stimuli such as light or heat, making them promising key materials for soft robots and artificial muscles. However, conventional liquid crystal elastomers have limitations in that they deform relatively slowly and have difficulty generating large amounts of force instantaneously.

To overcome these limitations, the researchers utilized the snap-through phenomenon, in which a structure that stores elastic energy―like an inverted umbrella or a bent hairpin―suddenly “snaps” into a reversed configuration once it reaches a critical point.

The researchers fabricated an azobenzene-based liquid crystal elastomer that responds to light in a bow-shaped arch structure. When exposed to ultraviolet light, changes in the molecular alignment within the material caused elastic energy to accumulate. Once the stored energy reached a critical level, the structure rapidly snapped through, generating fast motion.

The team then incorporated the attractive force of permanent magnets to lower the threshold for snap-through and enable the stored energy to be released more rapidly and powerfully. The maximum speed, which was approximately 140 mm per second when driven by light alone, increased to approximately 332 mm per second after the magnets were incorporated. The maximum actuation force also increased by approximately 14.6 times.

This does not mean that the magnets drive the device on their own. Rather, as the light-deformed liquid crystal elastomer approaches its critical point, magnetic force amplifies the final release of stored energy. In this way, the system structurally overcomes the low-output limitations of conventional soft actuators while preserving the flexibility and remote controllability of soft materials.

The research team also combined the developed actuator with fine, precisely fabricated polymer microneedles and verified their skin insertion performance. When exposed to light, the arch-shaped structure rapidly snaps downward, delivering a strong instantaneous impact to the microneedles and driving them into the skin.

Experiments showed that the microneedles were successfully inserted not only into gelatin structures designed to mimic skin, but also into actual pig skin tissue. In the pig skin, the microneedles reached an average depth of approximately 364 μm (micrometers), and a fluorescent substance used to simulate a drug was observed spreading around the insertion sites. The researchers also confirmed that the insertion depth and diffusion area of the substance could be controlled by adjusting the length and number of microneedles in the array.

The technology is considered to open up the possibility of “active smart livestock farming,” moving beyond conventional smart livestock systems that primarily monitor animal health through sensors to systems capable of performing actual treatment when needed. In the future, combining a reusable liquid crystal elastomer？magnet module with replaceable microneedle cartridges could enable the technology to be expanded into an automated precision treatment system.

Professor Dae-Seok Kim said, “The key to this study is that small molecular-scale deformations induced by light are amplified through a snap-through structure and magnetic force, converting them into a strong mechanical impact.” He added, “We expect this technology to find applications not only in smart livestock farming, but also in a wide range of fields requiring precise and remote control, including wearable medical devices, biointerfaces, and soft robotics.”

The paper presenting the research findings, titled “Snap-Through-Driven Liquid Crystal Elastomers for High-Power Remote Microneedle Actuation toward Smart Livestock Systems,” was published online on August 7 in 『Advanced Functional Materials』(IF: 19.9), a leading international journal in the field of materials science. <Pukyong Today>