Hydrogel-based strong and fast actuators by electroosmotic turgor pressure

• Published in: Science (American Association for the Advancement of Science) Vol. 376; no. 6590; pp. 301 - 307
• Main Authors: Na, Hyeonuk, Kang, Yong-Woo, Park, Chang Seo, Jung, Sohyun, Kim, Ho-Young, Sun, Jeong-Yun
• Format: Journal Article
• Language: English
• Published: United States The American Association for the Advancement of Science 15-04-2022
• Subjects: Actuation; Actuators; Deformation effects; Electric fields; Electrolytic cells; Fatigue limit; Hydrogels; Semipermeable membranes; Turgor
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.abm7862

Hydrogels are promising as materials for soft actuators because of qualities such as softness, transparency, and responsiveness to stimuli. However, weak and slow actuations remain challenging as a result of low modulus and osmosis-driven slow water diffusion, respectively. We used turgor pressure and electroosmosis to realize a strong and fast hydrogel-based actuator. A turgor actuator fabricated with a gel confined by a selectively permeable membrane can retain a high osmotic pressure that drives gel swelling; thus, our actuator exerts large stress [0.73 megapascals (MPa) in 96 minutes (min)] with a 1.16 cubic centimeters of hydrogel. With the accelerated water transport caused by electroosmosis, the gel swells rapidly, enhancing the actuation speed (0.79 MPa in 9 min). Our strategies enable a soft hydrogel to break a brick and construct underwater structures within a few minutes.