A Temperature-Compensated Differential Microstrip Sensor for Microfluidic Applications

The paper proposes a temperature-compensated sensor for microfluidic application. The sensor consists of a splitter/combiner section with two symmetrical complementary split-ring resonators (CSRR). A polydimethylsiloxane substrate is attached with the microfluidic channel aligned to the meander slot of the CSRR. A split-ring resonator (SRR) with peripheral circuit is added to detect environmental temperature. The water-methanol mixtures with various water fractions are measured at temperature ranging from 20°C to 50°C. The environmental temperature is firstly measured by the resonant frequency shift produced by SRR. Then, the variations in the resonant frequency and quality factor of the differential splitter/combiner section, as well as the temperature, are used as the input data for training the neural network. In comparison with previous designs, the proposed sensor is capable of not only suppressing the influences of environmental factors, but also retrieving the permittivity and loss tangent of liquid sample at specific temperature, thereby identifying the liquid accurately.