Actuation and locomotion driven by moisture in paper made with natural pollen.
A paper made from pollen grains can propel itself in response to humidity. This discovery provides an eco-friendly, biocompatible material for applications such as soft robots, artificial muscles and sensors.
A team at Nanyang Technological University, Singapore, prepared the material by incubating pollen grains in a hot alkaline solution and pouring the resulting gel into a Petri dish. The thickness and other important properties of the paper could be tweaked by adjusting the processing conditions.
The paper swelled when it absorbed water, but the close packing of the pollen particles prevented the water from diffusing. This meant that only the area in contact with the water swelled, causing the paper to curl. By combining two strips of different pollen densities, and hence different curling responses, the team created a swatch that propelled itself when exposed to humidity.
- PNAS 117, 8711–8718 (2020). doi: 10.1073/pnas.1922560117
|Nanyang Technological University (NTU), Singapore