Nanogap capacitors: Sensitivity to sample permittivity changes

Sensors based on nanogap capacitance changes are being developed for genomic and proteomic applications because they offer label-free detection on platforms amenable to high throughput configurations. We compare impedance spectroscopy measurements with a rigorously characterized model that predicts the impedance spectrum of these devices based on geometry. Sensitivity to permittivity changes is also predicted by the model and compared to the measured values in the frequency range from 1 Hz to 3 MHz. The lowest detection limit for the magnitude of the impedance (vertical bar Z vertical bar) is in the region of 100-0.2 MHz, and was measured to be a 1.7% change in permittivity across different devices. (c) 2006 American Institute of Physics.