Fig. 1. Hybrid characteristic and physical mechanism of REP. (a) Change of particle cluster observed when switching on and off a uniform AC electric field and a focused laser alternatively. (b) Interrelation of electrostatic, electrohydrodynamic and electrothermal forces involved in REP.
Fig. 2. Experimental setup for REP manipulation. (a) Schematic of REP experimental system. (b) Structure of a microfluidic chip to create REP manipulation environment.
Fig. 3. Various manipulations of 1μm-diameter polystyrene particles by REP. (a) Particle aggregation. (b) Particle translation. (c) Dynamic collection of particles. (d) Particle trapping in a continuous fluid flow. For the manipulations shown in (a)-(c), AC electric signal of 26.1kHz and 4.0Vpp and laser power of 20mW were provided to the microfluidic chip. The manipulation in (d) was achieved by 20.1kHz AC frequency, 5.4Vpp electric potential, and 20mW laser power. All the scale bars represent 10μm length.
Fig. 4. Manipulation of other kinds and types of colloidal particles by REP. (a) 1μm-diameter spherical latex particles. The AC electric signal and laser power applied for the manipulation are 15kHz, 7.1Vpp, and 20mW respectively. (b) 1μm-diameter spherical glass particles. The AC electric signal and laser power applied for the manipulation are 27.5kHz, 8.2Vpp, and 20mW respectively. (c) 1μm-diameter spherical magnetic particles. The AC electric signal and laser power applied for the manipulation are 28.8kHz, 6.1Vpp, and 20mW respectively. (d) Ellipsoidal glass particles. The ratio of major and minor axis of the particles is 1.2:1, and the length of the minor axis is 1μm. The AC electric signal and laser power applied for the manipulation are 11.9kHz, 6.8Vpp, and 20mW respectively. All the scale bars represent 10μm length.
Fig. 5. Demonstration of bio-compatibility of REP technique. (a) Aggregation of S. cerevisiae at arbitrary location on an electrode surface. (b) Dynamic trapping of S. cerevisiae along with movement of a focused laser. For the aggregation and dynamic trapping, AC electric signal of 8.87kHz and 6Vpp and laser power of 30mW were provided to the chip. The scale bars all represent 20μm length.