Actuation and locomotion driven by moisture in paper made with natural pollen

Abstract

Here we describe the development of a humidity-responsive sheet of paper that is derived solely from natural pollen. Adaptive soft material components of the paper exhibit diverse and well-integrated responses to humidity that promote shape reconfiguration, actuation, and locomotion. This mechanically versatile and nonallergenic paper can generate a cyclically high contractile stress upon water absorption and desorption, and the rapid exchange of water drives locomotion due to hydrodynamic effects. Such dynamic behavior can be finely tuned by adjusting the structure and properties of the paper, including thickness, surface roughness, and processing conditions, analogous to those of classical soapmaking. We demonstrate that humidity-responsive paper-like actuators can mimic the blooming of the Michelia flower and perform self-propelled motion. Harnessing the material properties of bioinspired systems such as pollen paper opens the door to a wide range of sustainable, eco-friendly, and biocompatible material innovation platforms for applications in sensing, actuation, and locomotion.

A Moisture‐Driven Actuator Based on Polydopamine‐Modified MXene/Bacterial Cellulose Nanofiber Composite Film

“…Smart actuators can transform other forms of energy into mechanical deformation from external stimuli such as humidity, [1] temperature, [2] light, [3] and magnetic/electric fields, [4] which show potential applications in the fields of artificial muscles, [5] soft robots, [6] sensors, and smart electrical devices. [7] In recent years, moisture-driven actuators have received increasing attention because they can convert chemical energy excited by water evaporation, a common phenomenon in natural environment, into mechanical energy generated by physical deformation.…”

Juglans Sporopollenin for High-Performance Supercapacitor Electrode Design

“… 11 − 13 Pollen has been also used in biomedical applications as a microrobot, actuator, and sensor. 14 − 18 However, their use in energy technologies is limited. 11 − 13 , 19 …”

Colloid‐Mediated Fabrication of a 3D Pollen Sponge for Oil Remediation Applications

“…[ 35 ] This discovery has opened the door to developing self‐actuating paper sheets derived from self‐assembling microgel particles and further motivates the exploration of advanced material fabrication strategies to create 3D scaffolds composed exclusively of pollen grains. [ 36 ] It is also advantageous that pollen grains—both in the natural form and as isolated exine capsules—possess a myriad of useful functional groups, including extensive surface hydroxylation, that can facilitate covalent and noncovalent attachment depending on the application. [ 31,37 ]…”