Hydrogel Thermostat Inspired by Photoprotective Foliage Using Latent and Radiative Heat Control

Se-Yeon Heo; Hyung Rae Kim; Yoonsoo Shin; Hyun Su Lee; Hyunkyu Kwak; Do Hyeon Kim; Dong Hyun Seo; Joo Hwan Ko; Hyo Eun Jeong; Sehui Chang; Min Seok Kim; Longnan Li; Jyotirmoy Mandal; Wei Li; Dae-Hyeong Kim; Young Min Song

doi:10.1002/adma.202516537

Hydrogel Thermostat Inspired by Photoprotective Foliage Using Latent and Radiative Heat Control

Adv Mater. 2025 Nov 4:e16537. doi: 10.1002/adma.202516537. Online ahead of print.

Authors

Se-Yeon Heo¹, Hyung Rae Kim^{1

2}, Yoonsoo Shin^{3

4}, Hyun Su Lee^{3

4}, Hyunkyu Kwak^{1

2}, Do Hyeon Kim^{1

2}, Dong Hyun Seo^{1

2}, Joo Hwan Ko⁵, Hyo Eun Jeong^{1

2}, Sehui Chang^{1

2

6}, Min Seok Kim¹, Longnan Li^{7

8}, Jyotirmoy Mandal⁹, Wei Li^{7

8}, Dae-Hyeong Kim^{3

4}, Young Min Song^{1

2

6

10

11}

Affiliations

¹ School of Electrical Engineering and Computer Science, Gwangju Institute of Science and Technology, Gwangju, 61005, Republic of Korea.
² School of Electrical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, 34141, Republic of Korea.
³ School of Chemical and Biological Engineering and Institute of Chemical Processes, Seoul National University, Seoul, 08826, Republic of Korea.
⁴ Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea.
⁵ Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
⁶ GIST InnoCORE AI-Nano Convergence Institute for Early Detection of Neurodegenerative Diseases, Gwangju Institute of Science and Technology, Gwangju, 61005, Republic of Korea.
⁷ GPL Photonics Laboratory, State Key Laboratory of Luminescence Science and Technology, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun, Jilin, 130033, China.
⁸ University of Chinese Academy of Sciences, Beijing, 100049, China.
⁹ Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ, 08544, USA.
¹⁰ AI Graduate School, Gwangju Institute of Science and Technology, Gwangju, 61005, Republic of Korea.
¹¹ Department of Semiconductor Engineering, Gwangju Institute of Science and Technology, Gwangju, 61005, Republic of Korea.

PMID: 41186023
DOI: 10.1002/adma.202516537

Abstract

Plants such as Populus alba feature photoprotective foliage that dynamically modulates optical properties to dissipate excessive heat under high temperatures, while condensation-induced latent heating preserves warmth under cold conditions-enabling tolerance to fluctuating thermal and hydric environments. Inspired by this natural strategy, a hydrogel-based thermostat is presented that balances latent and radiative heat fluxes. The system integrates lithium ions and hydroxypropyl cellulose into a polyacrylamide matrix, providing dynamic solar reflectance, high infrared emissivity, and reversible water sorption-desorption capabilities. Thermochromic and hygroscopic responses are tunable via adjustments in hydroxypropyl cellulose and lithium ions concentrations, allowing environment-specific adaptation. Mechanical robustness is enhanced by incorporating titanium dioxide nanoparticles and applying surface treatments. Experiments and simulations demonstrate both sub-ambient cooling and above-ambient heating across diverse conditions, establishing the system as an all-season thermal regulation platform.

Keywords: Populus alba–inspired thermal regulation; hydrogel thermostat; hygroscopicity; passive radiative cooling; thermochromism.

Abstract

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