Details

Autor(en) / Beteiligte

• Wang, Miao
• Tian, Xuelin
• Ras, Robin H. A.
• Ikkala, Olli

Titel

Sensitive Humidity‐Driven Reversible and Bidirectional Bending of Nanocellulose Thin Films as Bio‐Inspired Actuation

Ist Teil von

• Advanced materials interfaces, 2015-05, Vol.2 (7), p.np-n/a

Ort / Verlag

Weinheim: John Wiley & Sons, Inc

Erscheinungsjahr

2015

Quelle

Wiley Online Library

Beschreibungen/Notizen

• Inspired by plant movements caused by water swelling and deswelling within nano‐ and mesoscale cellulose fibrillar structures, asymmetric exposure of water vapors to thin films of nanofibrillated cellulose, NFC (also denoted as microfibrillated cellulose, MFC, or native cellulose nanofibers, CNF) is here shown to induce humidity‐controlled reversible actuation. The extent of the bending depends on the humidity difference across the film. A steady‐state bending is reached within a fraction of minute upon continued humidity exposure, and the film relaxes back upon removing the imposed humidity. The bending curvature becomes reduced when the film thickness increases, thus explaining that the effect is not observable in classic paper sheets, which are much thicker due to their constituent macroscopic thicker cellulose fibers. The bending is highly sensitive to humidity, as demonstrated by the observation that the film bends even based on the small humidity of human hand from a distance of several millimeters. Such a bending of a cellulose nanofiber film offers a particularly simple route toward biomimetic actuation and novel types of active material. Bioinspired reversible actuation of nanocellulose films by humidity stimulus is demonstrated with high sensitivity not attainable for classic paper sheets involving the thick pulp fibers. Unlike conventional bilayer actuators, which generally bend toward one specific direction, the nanocellulose films can bend in a bidirectional way, depending on the direction of the stimulus.