Sensors and Actuators B 117 (2006) 367–375 A novel fabrication of ionic polymer-metal composites (IPMC) actuator with silver nano-powders C.K. Chung a,∗ , P.K. Fung a , Y.Z. Hong a , M.S. Ju a , C.C.K. Lin b , T.C. Wu c a Department of Mechanical Engineering, Center for Micro/Nano Science and Technology, National Cheng Kung University, Taiwan, ROC b Department of Neurology, National Cheng Kung University, Taiwan, ROC c Industrial Technology Research Institute, Taiwan, ROC Received 6 June 2005; accepted 13 November 2005 Available online 15 December 2005 Abstract This article reports a novel approach of applying silver nano-powders to the fabrication of ionic polymer-metal composites (IPMC) actuator with good adhesion between the metal electrodes and polymer membrane without surface roughening pretreatment at low cost, high repeatability and short processing time. Micro-fabrication technologies are used for this IPMC actuator fabrication including the dissolving and casting of silver nano-particles (35 nm) in Nafion ® diluted solution, followed embossing, nontoxic electroless plating of silver, and microelectroforming of nickel. This IPMC actuator exhibits large deformation of bending curvature angle of more than 90 ◦ at lower driving voltage of 3 V. The frequency response of displacement with applied AC voltage of 2 V at 1 Hz results in a regular periodic deformations of the IPMC actuator. The elasticity modulus of the IPMC actuator can be reduced using an Ag–Nafion electrode for larger deformation than a pure Ag metal electrode. The electronic active polymer, IPMC, could be potentially used as the actuator of the active guide-wire, effective biomimetic sensor and artificial muscles. © 2005 Elsevier B.V. All rights reserved. Keywords: Ionic polymer-metal composites; Silver nano-powders; Actuator; Bio-MEMS 1. Introduction An electronic active polymer, ionic polymer-metal compos- ite (IPMC), could be developed into an actuator for the active guide-wire. This actuator generally consists of an electrical active polymer layer (Nafion ® 20%) sandwiched by two metal electrodes. It is able to bend the curvature through electrical conduction and has two major advantages of larger deformation and lower driving voltage. When driving voltage is provided, the IPMC membrane will bend toward the anode direction because the hydrophilic positive ions move toward cathode [1]. Fig. 1(a) and (b) shows the structure of perfluorosulfonic acid membrane and the schematic diagram of the deformation mechanism of IPMC, respectively. The cations like Na + , Li + and H + in the IPMC actuator generally exhibit better bending performance than others [2]. The biological compatibility of the IPMC actuator is very good [3] and, thus, it is suitable for detecting or actuating in the human body. However, the adhesion between polymer and ∗ Corresponding author. Tel.: +886 6 2757575x62111; fax: +886 6 2352973. E-mail address: ckchung@mail.ncku.edu.tw (C.K. Chung). electrode is a big problem during the fabrication of the IPMC actuator. To solve this problem, the electroless plating method had been used to fabricate the electrode layer, but it needed com- plex pretreatment to roughen the surface of polymer with high cost and time-consuming [4–6]. Therefore, other methods like hot-embossing, electroplating and polymer coating, etc. were provided for the adhesion promotion in decreasing the cost and time during fabrication [7–9]. Also, there are still some prob- lems during the fabrication of IPMC, such as the inability to stay humid, and the difficulty of avoiding electrolysis at higher applied driving voltage (>1.23 V) [10,11]. In this paper, we propose a novel approach of integrating the physical and chemical methods for the fabrication of IPMC actu- ator without surface roughening pretreatment for good adhesion at low cost and short processing time. They include the silver nano-powders casting, embossing, silver electroless plating and nickel electroforming technologies. 2. Experimental details IPMC actuators were fabricated using Nafion ® solution pro- duced by Du Pont Co. Ltd. The Nafion ® is one kind of ion 0925-4005/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.snb.2005.11.021