Travelling Wave Generation of Wrinkles on the Hydrogel Surfaces

• Published in: Macromolecular rapid communications. Vol. 43; no. 7; pp. e2100848 - n/a
• Main Authors: Kashihara, Yuka, Asoh, Taka‐Aki, Uyama, Hiroshi
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01-04-2022
• Subjects: Actuators; Compression; Electrophoresis; Fabrication; Hydrogels; Hydrogels - chemistry; polyion complexes; Skin Aging; surfaces; Traveling waves; Water; Wave generation; wrinkles; wrinkles; hydrogels; electrophoresis; surfaces; polyion complexes
• ISSN: 1022-1336; 1521-3927
• DOI: 10.1002/marc.202100848

The dynamic and static properties of structured surfaces have important functions in nature. In particular, wrinkles have important static roles, for example, increasing surface area, but dynamic roles of wrinkles remain poorly understood. Specifically, to understand and utilize the dynamic functions of wrinkles, it is necessary to observe wrinkle formation directly. In this study, a polyion complex (PIC) is formed on a hydrogel surface by electrophoresis, and the process of wrinkle formation through a transparent electrode is directly observed. By quantitative analysis of the wavelength and amplitude of wrinkles, it is found that the wrinkles move randomly in a wavy pattern in the initial stage of growing process. Furthermore, the direction of wavy motion of wrinkles is controlled by the compression of hydrogels in the in‐plane direction. The present study provides important insights into the fabrication of wrinkled surfaces with a controlled flow direction; opening the possibility for active wrinkles used in the development of functional surface structures as actuators that are capable of transporting small objects in water.
Wrinkle formation process on the hydrogel surface is directly observed using a microscope, and it is found that the wrinkles are moving in wavy and randomly during formation. Moreover, the direction of wavy motion can be controlled by compression of hydrogels in plane direction.