  For traditional capacitive pressure sensors, high nonlinearity and poor
sensitivity greatly limited their sensing applications. Hence, an innovative
design of capacitors based on spiral comb electrodes is proposed for
high-sensitivity pressure detection in this work. Compared to traditional
capacitive pressure sensors with straight plate electrodes, the proposed sensor
with the spiral electrodes increases the overlap areas of electrodes
sufficiently, the pressure sensitivity can thus be greatly improved. Moreover,
the capacitance variation of the proposed sensor is dominated by the change of
the overlap area of the electrodes rather than the electrode's distance, the
linearity can also thus be improved to higher than 0.99. Theoretical analysis
and COMSOL-based finite element simulation have been implemented for principle
verification and performance optimization. Simulation results show that the
proposed design has a mechanical sensitivity of 1.5x10-4 m/Pa, capacitive
sensitivity of 1.10 aF/Pa, and nonlinear error of 3.63%, respectively, at the
pressure range from 0 to 30 kPa. An equivalent experiment has been further
carried out for verification. Experimental results also show that both the
sensitivity and linearity of capacitive pressure sensors with spiral electrodes
are higher than those with straight electrodes. This work not only provides a
new avenue for capacitor design, but also can be applied to high-sensitivity
pressure detection.
