SEOULTECH researchers develop smarter, more controllable hydrogel pores

Hydrogels are soft, water-rich polymeric materials that can swell or shrink in response to environmental stimuli. This ability to change shape makes them valuable in miniaturized devices for flexible electronics, microrobotics, intelligent surfaces, and biomedical applications such as drug delivery. For example, hydrogel pores can be engineered to trap and release tiny drug particles on demand.

However, most current hydrogel pores use circular designs, which limit control over shape change and lead to unpredictable, slow actuation. They often close unevenly and recover poorly, reducing their precision and reliability.

To address these challenges, a research team led by Professor Hyunsik Yoon from the Department of Chemical and Biomedical Engineering at Seoul National University of Science and Technology in Korea, introduced a new origami-inspired folding strategy for reversible actuation of hydrogel pores. Prof. Yoon explains, “Unlike conventional circular pores, which result in randomized folding, our design involves a facet-driven folding strategy, integrating origami-inspired hinge-and-facet architectures into polygonal hydrogel pores, to enable programmable and predictable actuation.” The team also included Dr. Ji Hoon Kim and Professor Wo Bo Lee from Seoul National University. Their study was published in in Volume 8, Issue 7 of the journal Matter on June 30, 2025.

The proposed strategy uses polygonal pores with fixed boundaries and predetermined hinges for controlled pore closure and restoration. Upon swelling, the facets of the polygonal pores bulge inward toward the center of the pore along specific directions guided by the predetermined hinges at the vertices, ultimately closing the pore. When the hydrogel shrinks, the facets are restored along the same paths, achieving predictable restoration. Additionally, the extent of pore closure can be controlled by changing the polygonal shape and fine-tuning the geometric properties. Importantly, the polygonal pores retain 90% of their original shape after repeated swelling-shrinking cycles, demonstrating excellent reliability.

The researchers applied this strategy to achieve pH-triggered release of microparticles, where the pores release microparticles in a staged manner, based on the pH of the environment. “This pH responsive mechanism is highly useful for drug delivery applications, where drug release is staged and targeted to specific regions marked by pH fluctuations,” says Prof. Lee.

The researchers also explored information encryption using these pores by creating a mixed matrix of square and circular hydrogel pores, containing fluorescent particles. The difference in closing behavior between the two shapes allowed them to hide or reveal patterns, enabling one-time-use encryption.

“Our strategy can be integrated into drug delivery systems for achieving high spatial and temporal precision, improving therapeutic outcomes while minimizing side effects,” highlights Dr. Kim. “Moreover, this design opens new opportunities for advanced lab-on-a-chip systems, next-generation soft robotic components, and diagnostic assays.”

We hope this innovative facet-driven folding strategy is adopted into more hydrogel devices, enhancing both their controllability and reliability.

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Reference      
DOI: 10.1016/j.matt.2025.102248

About the institute Seoul National University of Science and Technology (SEOULTECH)
Seoul National University of Science and Technology, commonly known as 'SEOULTECH,' is a national university located in Nowon-gu, Seoul, South Korea. Founded in April 1910, around the time of the establishment of the Republic of Korea, SEOULTECH has grown into a large and comprehensive university with a campus size of 504,922 m2.

It comprises 10 undergraduate schools, 35 departments, 6 graduate schools, and has an enrollment of approximately 14,595 students.

Website: https://en.seoultech.ac.kr/

About Professor Hyunsik Hoon
Dr. Hyunsik Yoon, is currently a Professor in the Department of Chemical and Biomolecular Engineering at Seoul National University of Science and Technology.  He obtained his Ph.D from Seol National University in 2004. He has published over 80 articles that have received over 3000 citations to date. His research interests include polymer engineering and semiconductor processing.

About the Postdoctoral Researcher Ji Hoon Kim
Dr. Ji Hoon Kim, is a postdoctoral Researcher at the Energy and Environment Research Institute, Seoul National University of Science and Technology. He earned his Ph.D. in Chemical and Biological Engineering from Seoul National University, specializing in soft matter engineering.

About Professor Wo Bo Lee
Dr. Won Bo Lee, is a Professor in the School of Chemical and Biological Engineering at Seoul National University, specializing in nanomaterials theory and computational simulation. He obtained his Ph.D. in Chemical Engineering from University of California, USA in 2007.