Sensors and Actuators B 141 (2009) 256–262 Contents lists available at ScienceDirect Sensors and Actuators B: Chemical journal homepage: www.elsevier.com/locate/snb Three dimensional microelectrode array device integrating multi-channel microfluidics to realize manipulation and characterization of enzyme-immobilized polystyrene beads Ryouta Kunikata a , Yasufumi Takahashi a , Masahiro Koide a,b , Tomoaki Itayama b , Tomoyuki Yasukawa c , Hitoshi Shiku a , Tomokazu Matsue a,∗ a Graduate School of Environmental Studies, Tohoku University, 6-6-11 Aramaki-Aoba, Sendai 980-8579, Japan b Environmental Chemistry Division, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba 305-8506, Japan c Graduate School of Material Science, University of Hyogo, 3-2-1 Kouto, Kamigori-cho, Hyogo 678-1297, Japan article info Article history: Received 2 April 2009 Received in revised form 21 May 2009 Accepted 22 May 2009 Available online 31 May 2009 Keywords: Microfluidics Microelectrode array Chronoamperometry Dielectrophoresis Enzyme-immobilized beads abstract We microfabricated a novel device consisting of a 4 × 4 array microchamber sandwiched with the two microband electrode array. This device allows dielectrophoretic (DEP) manipulation of microbeads to introduce into and release out a certain address of the V-shaped microchamber, by applying AC volt- age (10 V pp , 10kHz) on the basis of DEP forces. The design and the position of the two electrodes (row and column electrodes) at each microchamber were optimized by simulation based on a finite element method. More importantly, electrochemical generation-collection measurement was possible to evaluate enzymatic activity. After microbeads immobilized with glucose oxidase (GOD) was entrapped in the V- shaped microchamber with DEP, a measuring solution containing 3mM ferrocenemethanol (FcCH 2 OH) and 0.1M glucose was introduced. The medium in the V-shaped microwell was immediately exchanged into the measuring solution whereas microbeads stayed within the microwell without applying DEP voltage, because the flow within the microchamber was isolated from that of the main channel. Then the potential of the row and column electrodes were set at 0.5 and 0.1V vs Ag/AgCl. The GOD activity can be monitored as the decrease in the [FcCH 2 OH] + reduction current. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Recent remarkable advances in microfluidics and sensor minia- turization provide rapid, cheap, and integrated analysis within closed microfluidic systems, creating a new class of portable, high- throughput analyzer. Sophisticated analytical device, frequently called as TAS (micro-total analysis system) device [1–3], requires development of manipulation technology for micro/nano objects. Among various methods, dielectrophoresis (DEP) has been used for sorting and separating particles and cells of interest because non- uniform electric fields can be formed using simple microelectrode arrays [4–19]. Taff and Voldman reported single cell patterning based on positive- (p-) [20] and negative-DEP (n-DEP) [21]. Fuchs et al. developed 320 × 320 electrode array for programmable manipu- lation of cells [22]. Recently, Westervelt and co-workers developed IC/microfluidic chip with 128 × 256 array of pixels to individually trap more than thousand cells in at once [23]. ∗ Corresponding author. E-mail address: matsue@bioinfo.che.tohoku.ac.jp (T. Matsue). Scalable electrode array has been already applied manipula- tion of microbeads and cells as mentioned above. On the contrary, high throughput electrochemical analysis is still difficult because conventional CMOS-based electrode array does not have enough sensitivity [24,25]. Very recently, we have introduced a novel electrochemical device to visualize n × n pixel of electrochem- ical activity with orthogonally crossing the arrays of the row and column band-shaped electrodes [26,27]. The electrochemi- cal recording was available based on redox cycling between the two electrodes positioned face-to-face with 10 m-separation. In the original device, 10 × 10 array of the measurement points with only 20 bounding pads for external connection. The row and col- umn electrodes were sequentially connected with a multiplexer to collect 100 data points within 22s. However, the gap between the facing electrodes was too small to manipulate microshpheres or living cells. Single cells randomly seeded within the SU-8 microchamber array, therefore 33% of the microwell was vacant [27]. Electrophoretic [28,29] and dielectrophoretic forces may sup- port to manipulate particles and cells with the combination of microfluidic devices. In the present study, band- and arch-electrodes are addressed orthogonally to fabricate a 4 × 4 array of measurement points with 0925-4005/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.snb.2009.05.028