Delivered by Ingenta to: Korea Advanced Institute of Science & Technology (KAIST) IP : 143.248.118.107 Tue, 31 Jul 2012 16:54:53 RESEARCH ARTICLE Copyright © 2011 American Scientific Publishers All rights reserved Printed in the United States of America Journal of Nanoscience and Nanotechnology Vol. 11, 5975–5979, 2011 Microvalves Based on Ionic Polymer-Metal Composites for Microfluidic Application Ji Sun Yun 1 , Kwang Suk Yang 2 ∗ , Nak-Jin Choi 2 , Hyung-Kun Lee 2 , Seung Eon Moon 2 , and Do Hyun Kim 1 ∗ 1 Department of Chemical and Biomolecular Engineering (BK21 Program), Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Republic of Korea 2 Electronics and Telecommunications Research Institute (ETRI), Daejeon, 305-700, Republic of Korea Simple and highly efficient microvalve systems based on an ionic polymer-metal composite (IPMC) diaphragm actuator have been developed. The microvalve system that was fabricated in this work operates when open and close voltage is applied, due to the phenomena of lithium ion flux and the subsequent electro-osmotic drag of water to the cathode. IPMC was prepared by compositing with platinum nanoparticles on both sides of Nafion ™ thin film. SEM images of the IPMC showed the high density and uniform size distribution of the Pt nanoparticles in the interpenetrating layer to ensure the proper performance of an IPMC actuator. The displacement of the IPMC for the microvalve was measured with a laser displacement meter. The application of open and close voltage made the operation of the valve faster. The fluorescence images of the flow in the fabricated IPMC-based microvalve system showed the successful operation of flow control in the microfluidic channel. The IPMC-based microvalve system shows a potential of IPMC for application as an actuator in microfluidic systems. Keywords: Ionic Polymer-Metal Composite (IPMC), PDMS Microchannel, Microvalve, Microfluidic Components. 1. INTRODUCTION A typical micro total analysis system (-TAS) and lab-on- a-chip system require components such as pumps, valves, and mixers for the effective manipulation of fluids. Such components are actuated by pneumatic, thermopneumatic, hydraulic, piezoelectric, electromagnetic, or electrostatic displacements. 1 2 Most of the conventional actuators for microvalve and micropumps are complex and expensive due to their sophisticated systems requiring precise con- trol. Electroactive-polymer (EAP) actuators, on the other hand, are known to have flexibility and large deforma- tion in spite of their slow response. These advantages of EAP ensure high actuator performance and provide a cost- effective solution to many actuator applications. Among the EAPs, ionic polymer metal composite (IPMC) is a thin polymer, usually Nafion ™ , Most of the conventional actuators for microvalve and microp- umps are complex and expensive due to their sophisticated systems requiring precise control. Electroactive-polymer (EAP) actuators, on the other hand, are known to have ∗ Authors to whom correspondence should be addressed. flexibility and large deformation in spite of their slow response. These advantages of EAP ensure high actua- tor performance and provide a cost-effective solution to many actuator applications. 3–8 The fabrication methods of and most concepts related to IPMCs were proposed by Oguro et al. 3 and Shahinpoor et al. 4 The effect of elec- trolytes and mobile cations on IPMCs was also investi- gated by them. The role of nanosized platinum particles in the performance improvement of IPMCs was studied by Kim et al. 9 Onishi et al. 10 proposed that via adsorption- reduction cycling, a nanoscale interpenetrating metal layer with a high interfacial area can be obtained within the polymer membrane. The application of an operating volt- age causes lithium ion flux and the subsequent electro- osmotic drag of water to the cathode, which results in swelling at the cathode side due to water enrichment and shrinkage at the anode side owing to water depletion. These phenomena induce the bending motion of IPMCs, which is necessary for the open/closed control of the IPMC-based microvalve system, as shown in Figure 1(a). In this study, simple and highly efficient microvalve systems were designed and fabricated by employing an IPMC actuator. A schematic illustration of the open/closed J. Nanosci. Nanotechnol. 2011, Vol. 11, No. 7 1533-4880/2011/11/5975/005 doi:10.1166/jnn.2011.4459 5975