A highly aromatic and sulfonated ionomer for high elastic modulus ionic polymer membrane micro-actuators

• Published in: Smart materials and structures 2012-05, Vol.21 (5), p.55015-1-7
• Main Authors: Hatipoglu, Gokhan, Liu, Yang, Zhao, Ran, Yoonessi, Mitra, Tigelaar, Dean M, Tadigadapa, Srinivas, Zhang, Q M
• Format: Article
• Language: English
• Subjects: Actuation; Actuators; Elastic modulus; Exact sciences and technology; General equipment and techniques; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Ionomers; Modulus of elasticity; Physics; Strain; Thin films; Transducers; Uptakes
• ISSN: 0964-1726; 1361-665X
• DOI: 10.1088/0964-1726/21/5/055015

A high modulus, sulfonated ionomer synthesized from 4,6-bis(4-hydroxyphenyl)-N,N-diphenyl-1,3,5-triazin-2-amine and 4,4′-biphenol with bis(4-fluorophenyl)sulfone (DPA-PS:BP) is investigated for ionic polymer actuators. The uniqueness of DPA-PS:BP is that it can have a high ionic liquid (IL) uptake and consequently generates a high intrinsic strain response, which is >1.1% under 1.6 V while maintaining a high elastic modulus (i.e. 600 MPa for 65 vol% IL uptake). Moreover, such a high modulus of the active ionomer, originating from the highly aromatic backbone and side-chain-free structure, allows for the fabrication of free-standing thin film micro-actuators (down to 5 µm thickness) via the solution cast method and focused-ion-beam milling, which exhibits a much higher bending actuation, i.e. 43 µm tip displacement and 180 kPa blocking stress for a 200 µm long and 5 µm thick cantilever actuator, compared with the ionic actuators based on traditional ionomers such as Nafion, which has a much lower elastic modulus (50 MPa) and actuation strain.