Enhanced photocontrollable dynamic adhesion of nematic elastomers on rough surfaces. (8th November 2022)

• Record Type: Journal Article
• Authors: Ohzono, Takuya; Koyama, Emiko
• Is Part Of: Polymer. Volume 260(2022)
• Publication Date: 2022-11-08
• Subjects: Nematic main-chain liquid crystal elastomer -- Adhesion -- Soft elasticity -- Rough surface -- Robot hands -- Light-induced phase transition; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2022.125377
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: Polymers with switchable adhesion properties are important for efficient catch-and-release processes in robotic hand applications and handgrips with on-demand adhesion control. However, counter objects often have a rough surface topography, which requires a dynamic adhesion system that balances adhesion and detachment performances. Here, we demonstrate that a photosensitive nematic main-chain liquid crystal elastomer (LCE) has suitable photoswitchable adhesion properties on surfaces with micrometer-scale roughness, resulting in a large adhesion change. The nematic LCE exhibits the so-called "soft elasticity, " wherein it can deform at a certain strain without increasing the elastic energy. Such deformation can be maintained owing to arrested relaxation, enabling the LCE to deform along with a rough surface upon light pressure. This increases the contact area and consequently enhances adhesion ability. On the other hand, the LCE exhibits rubber elasticity after proper light irradiation owing to a phase transition from the nematic to the isotropic phase. As rubber elasticity limits deformation, the contact area on the rough surface, and thus the adhesion, is greatly reduced. This LCE with photoswitchable elasticity has great merit as a dynamic adhesive pad for treating objects with rough surfaces, which may expand the versatility of stimuli-responsive adhesive systems. Graphical abstract: Enhanced photocontrollable dynamic adhesion of nematic liquid crystal elastomers (LCEs) on rough surfaces was demonstrated and explained by the contact state difference. Image 1 Highlights: A photosensitive nematic main-chain liquid crystal elastomer (LCE) was synthesized. The LCE exhibits the soft elasticity only in the nematic phase. The LCE can deform along the rough counter surface, leading to the higher adhesion. The photo-induced normal elasticity reversibly lowers the adhesion. Photocontrollable dynamic adhesion are enhanced on rough surfaces.