PCR microchip. The PCR microchip was made up of two
25.4625.460.5 mm3 glass slides, where the bottom slide has a
stationary reaction chamber holding the PCR sample and the top
slide has a thin film heater to precisely and uniformly control the
reaction chamber temperature (Figure 1B). The circular reaction
chamber in the bottom glass slide (diameter: 7.8 mm, depth:
80 mm) holds 8-ml of PCR sample to be amplified. Two different
size holes were made as the inlet and outlet (2 mm and 1 mm in
diameter, respectively) of the reaction chamber, in order to load
samples into the reaction chamber through the 2 mm hole and to
extract amplified samples from the reaction chamber through the
1 mm hole for off-chip validation. When loading samples through
a 2 mm hole, samples can easily fill the entire reaction chamber
due to capillary force. However when injecting samples through a
1 mm hole that tightly fits to a pipette tip (1–200 ml, VWR, Sugar
Land, TX, USA), samples tend to flow only along one side of the
reaction chamber from time to time and did not fill the entire
reaction chamber so that an air bubble is formed in the chamber.
This air bubble expands during thermocycling, making it difficult
to properly measure the fluorescence of liquid sample. When
extracting samples, the 1–200 ml pipette tip was tightly plugged
into the 1 mm hole and vacuum was applied to completely extract
the sample in the reaction chamber. By forming a tight seal
between the 1 mm hole and the pipette tip, amplified samples
were efficiently extracted.