Biomedical Engineering Reference
In-Depth Information
TAble 4.1
List of Catastrophic Defects for Biochips
Number
of Cells
Involved
in the
Defect
Cause of Defect
Defect Type
Fault Model
Observable Error
Excessive
actuation
voltage applied
to an electrode
Dielectric
breakdown
1
Droplet-electrode
short (a short
between the
droplet and the
electrode)
Droplet undergoes
electrolysis,
which prevents its
further
transportation
Electrode
actuation for
excessive
duration
Irreversible
charge
concentration
on an electrode
1
Electrode-
stuck-on (the
electrode
remains
constantly
activated)
Unintentional
droplet operations
or stuck droplets
Excessive
mechanical force
applied to the
chip
Misalignment of
parallel plates
(electrodes and
ground plane)
1
Pressure gradient
(net static
pressure in some
direction)
Droplet
transportation
without activation
voltage
Coating failure
Nonuniform
dielectric layer
1
Dielectric islands
(islands of
Teflon coating)
Fragmentation of
droplets and their
motion is
prevented
Abnormal metal
layer deposition
and etch
variation during
fabrication
Grounding
failure
1
Floating droplets
(droplet are not
anchored )
Failure of droplet
transportation
Broken wire to
control sources
1
Electrode open
(electrode
actuation is not
possible)
Failure to activate
the electrode for
droplet
transportation
Metal connection
between two
adjacent
electrodes
2
Electrode short
(short between
electrodes)
A droplet resides
in the middle of
the two shorted
electrodes, and its
transport along
one or more
directions cannot
be achieved
Particle
contamination
or liquid residue
A particle that
connect two
adjacent
electrodes
2
Electrode short
Protein
absorption
during a
bioassay
Sample residue
on electrode
surface
1
Resistive open at
electrode
Droplet
transportation is
impeded
Contamination
Assay results are
outside the range
of possible
outcomes
