User`s guide

Contents ▲ 583 ▼ Index
Electrokinetic forces
Electrokinetic forces are used to move, switch and separate the samples. Active control
over voltage gradients directs the movement of materials using the phenomenon of
electrophoretic flow.
Electroosmotic Flow
A phenomenon that results from an electrical double layer formed by ions in the fluid and
surface electrical charges immobilized on the capillary walls. When an electric field is
applied, the bulk solution moves towards one of the electrodes. This phenomenon can be
used to move fluids through microfabricated channels.
Electrophoresis
A standard technique of separating molecules on the basis of their mobility
(charge-to-mass ratios). An electrical potential is applied across a capillary containing a
sample in a fluid medium. Positive molecules migrate towards the cathode and negative
molecules migrate towards the anode at different speeds, depending on their
electrophoretic mobility.
Electrophoretic flow
A macroscopic phenomenon that results from an electrical double layer formed by ions in
the fluid and surface electrical charges immobilized on the capillary walls. When an
electric field is applied, the bulk solution moves towards one of the electrodes (cathode).
Electrodes sit in the reservoirs that connect to the ends of the various channels.
Electrode potentials are applied to the various reservoirs in a time-dependent fashion to
move the fluid in the required direction. The gel-filled channels of the LabChip devices do
not exhibit a measurable flow because of dynamic channel coating and viscosity of the
polymer matrix.