  A multichannel thin-film sensor is implemented from a set of
microstrip-coupled split-ring resonators (SRR's) with different dimensions.
Each SRR exhibits a unique high-Q resonance that is sensitive to the presence
of a sample in a particular area. Hence, this SRR-based sensor can function (i)
to detect different samples simultaneously to increase the throughput or (ii)
to characterise nominally identical samples at multiple frequencies to increase
the sensor selectivity. The design principle is validated with simulation and
measurement. Owing to the optimized design, sensing a low-permittivity film
with a thickness as small as one thousandth of the operating wavelength is
achievable.
