Supporting information for. Microfluidic Impedance Cytometer with Inertial Focusing and. Liquid Electrodes for High-Throughput Cell Counting and

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Cornelius Rodgers
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1 Supporting information for Microfluidic Impedance Cytometer with Inertial Focusing and Liquid Electrodes for High-Throughput Cell Counting and Discrimination Wenlai Tang, Dezhi Tang, Zhonghua Ni, Nan Xiang* and Hong Yi * School of Mechanical Engineering, Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, Southeast University, Nanjing, , China * s: nan.xiang@seu.edu.cn (Nan Xiang), yihong@seu.edu.cn (Hong Yi) Text S-1: Dimensions of the microfluidic device The microfluidic device employed in this work consists of an asymmetrically curved microchannel and a liquid-electrode detection region. The curved microchannel has a total of 20 S-shaped units followed by a straight channel with a length of 16 mm. Each S-shaped unit consists of one small turn and one large turn, their detailed dimensions are listed in Table S-1. The detection region locates at the intersection of main channel and two side channels. The widths of both main channel and side channel are 50 μm. All the microchannels have a rectangular cross-section and a channel height of 25 μm. Two large circular electrode chambers connected with side channels have a diameter of 4 mm. For the condition of the tested smallest particles/cells (a p = ~10 μm) flowing at a flow rate of 100 μl/min, the channel dimensions designed in this work satisfy the design rules for inertial focusing in curved channels (a p 2 r/h 3 = 0.64 > 0.04 and L = fπμw 2 /(ρu m a p 2 f L ) = mm < 16 mm, where w is the average width of small turns and large turns (150 μm), μ is the dynamic viscosity of ~0.001 Pa s, ρ is the fluid density of ~1000 kg/m 3, the lift coefficient f L and the factor f are selected as 0.05 and 0.5, respectively). S-1

2 Table S-1. Detailed dimensions of the curved microchannel. Unit Width (μm) Small radius (μm) Large radius (μm) Eccentricity (μm) Small turn No Large turn S-2

3 Table S-2. A list of the detection throughput of typical impedance-based microcytometers. Techniques Throughput (cells/s) Reference Polyelectrolytic salt bridge-based electrodes 1000 Chun 1 Constriction channel Zheng 2 Parallel facing electrodes 100 Holmes 3 Parallel facing electrodes Cheung 4 Parallel facing electrodes 1000 Spencer 5 S-3

4 Figure S-1. (a) Schematic diagram illustrating the balanced forces acting on particle in channel cross-section. The fluid field contour represents the distribution of main flow and the black arrows indicate the velocities of secondary flow. The particles occupy their stable equilibrium positions close to inner channel wall. (b) Spatial distributions of three differently sized particles passing near the curved channel outlet at flow rates ranging from 50 to 250 μl/min with an interval of 50 μl/min. (c) Lateral focusing positions of three differently sized particles at flow rates ranging from 100 to 250 μl/min with an interval of 50 μl/min. The inset is the stacked image series showing the spatial distributions of mixed particles passing through main channel at a flow rate of 100 μl/min. (d) Simulation results of the electric field distributions near detection region using the AC/DC module of COMSOL Multiphysics. For simplification, the entire volume was filled with pure PBS solution (σ m = 1.6 s/m, and ε r = 80) and all the boundaries were electrically insulated. A potential of 1 V was applied to the cylindrical electrodes which located in the center of electrode chambers. An insulating sphere (15 μm diameter) was included to consider the influence caused by the existence of particle. S-4

5 Figure S-2. (a) High-speed microscope images illustrating that the particle (10 μm) translocation through detection region. The calculated duration for the particle translocation is ~0.09 ms. (b) Corresponding impedance peak with a width of ~0.15 ms. S-5

6 Figure S-3. Detection accuracy rates of our microcytometer at different particle concentrations ranging from particles/ml to particles/ml. The accuracy rate was calculated as the ratio of the number of normal impedance peaks to the total number of tested particles (n 500). S-6

7 Figure S-4. (a) Representative impedance peaks of a WBC with a 10 μm particle. (b) Representative impedance peaks of a MCF-7 cell with a 15 μm particle. (c) Representative impedance signals of pure MCF-7 cells. The green dash line represents the peak amplitude threshold (3.5) selected in our work for discriminating MCF-7 cells and WBCs. There is a total of 75 cells detected in a time period of 1.5 s. S-7

8 References (1) Chun, H. G.; Chung, T. D.; Kim, H. C. Anal. Chem. 2005, 77, (2) Zheng, Y.; Shojaei-Baghini, E.; Azad, A.; Wang, C.; Sun, Y. Lab Chip 2012, 12, (3) Holmes, D.; Morgan, H. Anal. Chem. 2010, 82, (4) Cheung, K. C.; Di Berardino, M.; Schade-Kampmann, G.; Hebeisen, M.; Pierzchalski, A.; Bocsi, J.; Mittag, A.; Tarnok, A. Cytometry, Part A 2010, 77A, (5) Spencer, D.; Hollis, V.; Morgan, H. Biomicrofluidics 2014, 8, S-8

Model of an Interdigitated Microsensor to Detect and Quantify Cells Flowing in a Test Chamber.

Excerpt from the Proceedings of the COMSOL Conference 2010 Paris Model of an Interdigitated Microsensor to Detect and Quantify Cells Flowing in a Test Chamber. Elena Bianchi * 1,3, Federica Boschetti 1,