Researchers report a pollen-based paper that is sensitive to humidity and can act as a tunable actuator. Smart actuator materials are sought after in applications such as soft robots, energy generators, and sensors, and some natural materials possess desired properties for such smart technologies. Juha Song, Nam-Joon Cho, Subra Suresh, and colleagues created a type of paper derived from natural pollen. The paper uses nonallergenic and inexpensive pollen grains from sunflowers that have been converted to soft microgels via a traditional soap-making process and dried in a self-assembling structure. The properties of the microgels make them highly responsive to humidity, and the design of the paper can incorporate variations in thickness and surface roughness to fine-tune responsiveness. When held on a bare human palm, the paper absorbs enough moisture to curl and quickly resumes its flat shape when transferred to a dry surface. When the paper is arranged into an apparatus mimicking the petals of the Michelia flower and inserted into a vial of water, the absorption of water vapor causes the paper petals to expand, similar to the flower's blooming motion, showing the paper's self-actuation and environmental sensitivity. According to the authors, the pollen-based paper is a low-cost, highly tunable material ideal for various actuation applications.
Article #19-22560: "Actuation and locomotion driven by moisture in paper made with natural pollen," by Ze Zhao et al.
MEDIA CONTACT: Foo Jie Ying, Nanyang Technological University, SINGAPORE; e-mail: jieying@ntu.edu.sg
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Proceedings of the National Academy of Sciences