Synthetic Metals 157 (2007) 523–528 Sonication time effect on MWNT/PANI-EB composite for hybrid electro-active paper actuator Sungryul Yun, Jaehwan Kim ∗ Center for EAPap Actuator, Department of Mechanical Engineering, Inha University, 253 Yonghyun-Dong, Nam-Ku, Incheon 402-751, South Korea Received 21 January 2006; accepted 20 May 2007 Available online 27 July 2007 Abstract This paper investigates the multi-walled carbon nanotubes (MWNT) and emeraldine formed polyaniline (PANI-EB) composite coating on electro-active paper (EAPap) actuator. EAPap is made with a cellulose paper by coating thin electrodes on both sides of the paper. When an electric field is applied across the electrodes the paper generates a bending displacement. This EAPap material has merits in terms of lightweight, low actuation voltage, low power consumption, dryness, biodegradability and low price. However, the force output and the actuation frequency band are low. Thus, the MWNT with PANI-EB composite is coated on EAPap material to improve its performance as an actuator. This is termed as a hybrid EAPap actuator. The fabrication process of the composite and the actuator performance are explained. In the fabrication process of the composite, the weight percents of MWNT and PANI-EB, and the sonication time have significant effect on the characteristics of the composite as well as the performance of the hybrid EAPap actuator. The weight percents of MWNT and PANI-EB were chosen by considering the electrical property as well as the process capability of the composite. The composites are made with different sonication times, from 2 h to 5 h, and their characteristics are analyzed using FT-IR, TGA, SEM and electrical conductivity measurement. The structural enhancement and electrical conductivity change associated with the sonication time are explained based upon the strong bonding and ionic interaction of MWNT and PANI-EB constituents. Based on the analysis results of the composite, the actuation performance of the hybrid EAPap actuator is evaluated in terms of bending displacement, blocking force, electrical power consumption and efficiency along with sonication time. © 2007 Elsevier B.V. All rights reserved. Keywords: Electro-active paper (EAPap); Multi-walled carbon nanotubes (MWNT); Polyaniline emeraldine base (PANI-EB); Sonication; Bending displacement; Blocking force 1. Introduction In the last decade, the field of smart materials has received much attention as a result of the development of new electro-active polymer (EAP) materials that exhibits a large displacement [1–3]. This characteristic is a valuable attribute that has enabled a myriad of potential applications, and it has evolved to offer operational similarity to biological muscles. The application of EAP devices requires the availability of their properties at various operating conditions. Especially, for micro- insect robots and micro-flying objects, a new and innovative EAP material that meets the requirements of ultra-lightweight and low power consumption must be created. Thus, it is neces- ∗ Corresponding author. Tel.: +82 32 860 7326; fax: +82 32 868 1716. E-mail address: jaehwan@inha.ac.kr (J. Kim). sary to develop a new EAP actuator with ultra-lightweight, fast response, robustness and low power consumption. Since papers are lightweight, cheap and biodegradable, these materials are very attractive for bio-mimetic actuators. Also, these materials can be suitable for biosensors and immuno-sensors because of their good acceptability with organics. As a pioneering attempt, cellulose paper has been investigated as an active material that can generate bending displacement in the presence of electric field across the electrodes. This active material is termed as electro-active paper (EAPap) [3]. EAPap is made by coating thin gold electrodes on both side of cellulose paper. It has many advantages in terms of lightweight, large dis- placement, low activation voltage and low power consumption. Previous research on EAPap actuator and conductive polymer (polypyrrole and polyaniline) coated EAPap [4] have shown the potential of cellulose paper as soft robotic actuator and artificial muscle. However, EAPap needs to overcome its’ drawbacks of 0379-6779/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.synthmet.2007.05.016