3D focusing of nanoparticles in microfluidic channels

Applied Physics Letters

Ramos

et al. 2007

Self Cite

The control and handling of fluids are central to many applications of the lab on chip. We report how alternating current ͑ac͒ electric fields can deflect and manipulate coflowing streams of two different electrolytes within a microfluidic channel. The two different electrolytes flow side by side over an array of interdigitated electrodes which occupies the width of the channel. Application of a 20 V ͑peak to peak͒ voltage at 1 MHz to the electrodes causes the liquid with higher conductivity to occupy a larger region of the channel. This effect causes a significant displacement of the boundary between the two fluids.

mentioning

confidence: 99%

Control of two-phase flow in a microfluidic system using ac electric fields

Morgan

Applied Physics Letters

Ramos

et al. 2007

Self Cite

“…This plot is identical to that obtained from numerical simulation. 9 In the experiments, particles flow through the channel in the gap between two adjacent electrodes. Therefore, particles are pushed toward point A, focusing into a stream.…”

Section: ͑10͒mentioning

confidence: 99%

“…By using negative DEP ͑nDEP͒, the particles are repelled from the electrode edges and focused into a tight stream in the channel center. [8][9][10][11] Since the electrodes are long compared to their width, the electric field analysis can be performed through a cross section of the device, 9 as shown in Fig. 1͑b͒.…”

mentioning

confidence: 99%

Analytical solutions for the electric field and dielectrophoretic force in a dielectrophoretic focusing electrode structure

Sun

Applied Physics Letters

Morgan

2008

The analysis of the movement of particles in a nonuniform field requires accurate knowledge of the electric field distribution. In this letter, the Schwarz-Christoffel mapping method is used to analytically solve the electric field distribution in a dielectrophoretic focusing electrode structure. The analytical result for the electric field distribution is validated by comparison with numerical simulations using the finite element method. The electric field solution is used to calculate the dielectrophoretic force on a particle in the system. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2916827͔ Dielectrophoresis ͑DEP͒ 1-3 is one of the ac electrokinetic techniques where the interaction between a fieldinduced dipole moment on the particle and a nonuniform electric field produces a force on the particle. Since the dielectrophoretic forces are generated from the interaction between the electric field and the induced dipole, it is important to characterize the strength and direction of the electric field distribution in the system.In this work, we use the Schwarz-Christoffel mapping ͑SCM͒ method 4-7 to calculate the electric field generated by the dielectrophoretic focusing electrode structure shown in Fig. 1͑a͒. By using negative DEP ͑nDEP͒, the particles are repelled from the electrode edges and focused into a tight stream in the channel center. [8][9][10][11] Since the electrodes are long compared to their width, the electric field analysis can be performed through a cross section of the device, 9 as shown in Fig. 1͑b͒. Since the electrodes are much thinner than their width, they can be represented as a section of the bottom boundary at a fixed potential. The Neumann boundary condition ͑insulating͒ is used for the potential at the electrolyte/ glass interfaces. 6,12,13 Applying symmetry, only a quarter of the system ͑ABCDEF͒ needs to be solved in the analysis. Figure 1͑c͒ shows the three complex planes used for the SCM procedure. The selected cell ABCDEF is rotated 90°a nd set in the Z plane with the boundary conditions for as shown: ‫ץ‬ / ‫ץ‬n = 0, along the insulating walls BC, CD, and EF. Dirichlet boundary conditions define the fixed potential = V along the electrode ͑DE͒ and the boundary for the axis of the odd symmetry, =0 ͑AF and AB͒. The interior of the polygon ABCDEF in the Z plane is mapped into the upper half of the T plane by using the SCM method. The polygon ABCDEF is opened at point G and the boundaries of the polygon mapped to the real axis of the T plane. The coordinates of the corresponding points Z A -Z F in the T plane are T A -T F , respectively. The point G is mapped to positive and negative infinities. The SCM integral 14 from the T plane to the Z plane is given by

“…The focussing system has been described in detail elsewhere, [17][18][19] and will only briefly be discussed here. A suspension of latex beads suspended in dilute PBS (300 mSm…”

Section: Dep Focussing and Optical Detectionmentioning

confidence: 99%

On-chip high-speed sorting of micron-sized particles for high-throughput analysis

Holmes

Sandison

IEE Proc., Nanobiotechnol.

et al. 2005

Self Cite

A new design of particle sorting chip is presented. The device employs a dielectrophoretic gate that deflects particles into one of two microfluidic channels at high speed. The device operates by focussing particles into the central streamline of the main flow channel using dielectrophoretic focussing. At the sorting junction (T-or Y-junction) two sets of electrodes produce a small dielectrophoretic force that pushes the particle into one or other of the outlet channels, where they are carried under the pressure-driven fluid flow to the outlet. For a 40 mm wide and high channel, it is shown that 6 mm diameter particles can be deflected at a rate of 300/s. The principle of a fully automated sorting device is demonstrated by separating fluorescent from non-fluorescent latex beads.