Chip fabrication and real pictures. (a) Fabrication process flow of a 3D integrated microfluidic chip: the lower and upper channels as well as the chip are fabricated separately before being plasma bonded; (b) real image of fabricated microfluidic chip containing 13 channels in a small area; (c) optical microscope image of the electrodes configuration in the region indicated by red dashed square in 1(b). The arrowhead shaped electrode is designed for trapping particles by AC signal, while the circle shaped electrodes are used for manipulating particles by DC signal.
Simulation of electric field intensity and DEP force. (a) Electric field intensity distribution of arrowhead 3D electrode at the middle plane between upper electrode and lower electrode. The schematic diagram of 3D electrode is shown in the inset of (a). The potential was set to 1 V and −1 V for upper electrode and lower electrode, respectively. The red color represents high electric field, while the blue color represents low electric field. The black lines represent electrode edges; (b) cross-sectional view of field distribution and DEP force along the red dashed line in 2(a); (c) cross-sectional view of field distribution and DEP force of planar electrode located on one side of microchannel. The magnitude of DEP force was normalized by logarithm function with base of 10.
Accumulation of 10 μm PS particles by applying AC signal of 21 Vpp at 50 kHz with field strength of 7 × 106 V/m on the arrowhead electrode. (a) t = 10 s; (b) t = 30 s; (c) t = 60 s; (d) t = 90 s. The channel depth was 30 μm.
Optical images of the whole trapping region containing 13 channels in total and several individual channels indicated by red dashed squares. It shows that every channel could be used for trapping particles.
Trapping of yeast cells in four channels to demonstrate the capability of pre-concentration of bioparticles by the proposed device. Pictures were taken after applying a trapping signal for 2 min. The applied AC signal was 10 Vpp at 50 kHz and the channel height was 15 μm. The medium conductivity was adjusted to 140 μS/cm for collection of yeast cells by negative DEP.
Capture and release of yeast cells. (a), (b) Capture of yeast cell by positive DEP at medium conductivity of 2 μS/cm. Yeast cells were collected between upper electrode and lower electrode where the electric field strength was highest. Flow was driving by difference of water level between inlet and outlet. The applied AC signal was 5 Vpp at 50 kHz and the channel height was 15 μm. (c)–(f) Release of yeast cells by applying DC field of 700 V/m after collection of yeast cells for 55 s. These figures demonstrated that yeast cells travelled in the same direction as the electric field.
Collection and release of E. coli. (a), (b) Collection of E. coli by negative DEP at medium conductivity of 380 μS/cm at t = 0 s and t = 120 s, respectively. AC signal of 15 Vpp at 50 kHz was applied in the channel of 15 μm in depth; (c), (d) Collection of E. coli by positive DEP at medium conductivity of 2 μS/cm and release of E. coli after trapping for 1 min. E. coli bacteria were collected between upper electrode and lower electrode in 8c. The applied AC signal was 10 Vpp at 50 kHz and the channel height was 15 μm. The applied DC field for releasing was 700 V/m.
The real part of CM factor as a function of electric field frequency for live (red line) and dead (blue line) yeast cells at medium conductivity of 140 μS/cm. Positive value of real part of CM factor represents yeast cells under positive DEP, while the negative value represents cells under negative DEP. The violet dashed line indicates the working frequency for separating them due to the difference in DEP forces. The inset is the optical microscope image of mixture of live and dead yeast cells dyed by two colors.
The separation process of live and dead yeast cells with time interval of 5 s. The applied AC signal was 3 Vpp at 50 kHz and electric field was 1.0 × 103 V/m. The channel height is 30 μm. Live yeast cells experienced large DEP force were trapped at the tip of arrowhead electrode, while dead yeast cells moved towards the outlet under electrokinetic force. Some dead yeast cells are highlighted by orange dashed circles for a better view.
Article metrics loading...
Full text loading...