Figure 2

(a) 3D schematic of an electrofluidic device consisting of a closed microchannel integrated with a pair of planar microelectrodes for 1D electromanipulation of Euglena cells. The inset shows an optical micrograph of microelectrodes in the microchannel. Swimming behavior of Euglena cells between a pair of microelectrodes in the (b) absence and (c) presence of an electric field (20 Vp-p, 0.5 MHz). ‘ON’ and ‘OFF’ correspond to experiments with and without electric power, respectively. The blue arrow indicates the electric field direction, which is the same as the swimming direction of the oriented cells. The scale bars indicate 200 μm. (d) Simulated electric-field distributions in the central areas of the X–Z and X–Y planes in the microchannel in (a–c). The simulation parameters are as follows: the electrical conductivities of the metal electrode and the Euglena cell solution are 2.17×10⁷ S m⁻¹ (Ref. 36) and 0.096 S m⁻¹, respectively. The refractive indices of the solution and the glass are 1.333 and 1.515, respectively. The electric potential difference between the electrodes is set to 20 V. (e) Quantitative analysis of the electro-orientation of cell motions in the electrofluidics, showing the cell alignment ratio versus applied voltage (Vp-p). The frequency of the applied electric field and the conductivity of the Euglena cell solution are maintained at 0.5 MHz and ~0.091 S m⁻¹, respectively.