We report on two types of electrodes that enable the integration of optoelectronic tweezers (OETs) with multilayer poly(dimethylsilane)- (PDMS-) based microfluidic devices. Both types of electrodes, Au-mesh and single-walled carbon nanotube- (SWNT-) embedded PDMS thin film, are optically transparent, electrically conductive, and can be mechanically deformed and provide interfaces to form strong covalent bonding between an OET device and PDMS through standard oxygen plasma treatment. Au-mesh electrodes provide high electrical conductivity and high transparency but are lack of flexibility and allow only small deformation. On the other hand, SWNT-embedded PDMS thin film electrodes provide not only electrical conductivity but also optical transparency and can undergo large mechanical deformation repeatedly without failure. This enables, for the first time, microfluidic integrated OET with on-chip valve and pump functions, which is a critical step for OET-based platforms to conduct more complex and multistep biological and biochemical analyses. 1. Introduction Optoelectronic tweezers (OETs) demonstrated by Chiou et al. in 2005 have promised a platform for high-throughput single cell manipulation and analysis [1, 2]. The principle of manipulating microscale objects and cells on an OET platform is based on light-patterned virtual electrodes and the induced dielectrophoretic (DEP) forces [1]. Types of objects that have been manipulated using OET are versatile, including polystyrene beads [1, 2], semiconductor microdisks [3], nanowires [4], DNA molecules [5], proteins [6], sperm [7], and bacteria and mammalian cells [1, 2, 8–10]. Recent development of OET technologies also broadened the type of media in which OET can operate. Phototransistor OET enabled OET to function in regular physiological buffers with high electrical conductivity (1.5？S/m) [11]. Floating electrode OET enabled the manipulation of aqueous droplets in electrically insulating media such as oils and air [12, 13]. OET can also be integrated with digital microfluidic platform for manipulating objects carried in droplets [13, 14]. A universal platform successfully integrating OET and optoelectrowetting (OEW) further allows optical manipulation of objects and droplets on the same featureless OET device [15]. Integration of OET with continuous phase microfluidic devices has also been realized [16, 17]. However, the integration is currently limited to simple microfluidic channels without other functional components such as valves and pumps due to the rigid and brittle property of ITO electrodes. This
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