Improved Hairpin Resonator for Microfluidic Sensing

Abstract

We present a near-field microwave sensor based on a hairpin resonator for detecting aqueous ethanol and aqueous NaCl concentrations in microfluidics. A hairpin sensor with a high-quality (high-Q) dielectric resonator allows the detection of a small variation in the aqueous NaCl concentration by measuring the scattering parameter (S 21) responses at resonance frequencies. The responses caused by the test liquids with various dielectric constants in aqueous ethanol solution were observed at operating frequencies of 1.9 and 2.1 GHz. The detection of various concentrations of NaCl in solution was also achieved. The changes in S 21 at resonance frequencies are directly related to changes in the aqueous NaCl concentration because of the electromagnetic interaction between the resonator and the NaCl solution. The stable linear relationships are advantageous for detecting and analyzing aqueous ethanol and aqueous NaCl concentrations. It shows that the sensor is reliable for both dielectric constant and conductivity detection in liquid. The hairpin resonator, which is easily fabricated by standard printed circuit board (PCB) technology, has great potential for microfluidic sensing applications.

High-sensitivity radio frequency noncontact sensing and accurate quantification of uric acid in temperature-variant aqueous solutions

“…adio frequency (RF) resonator-based noncontact sensors, which have emerged as powerful spectroscopic tools for various applications, such as oil and energy, [1][2][3] biomedical, 4,5) health, 6) environmental, 7) and dielectric characterizations of aqueous solutions, [8][9][10] principally detect the changes in material dielectric properties in a nonintrusive and nondestructive manner. These sensors generate considerable interest in terms of their ability to deeply penetrate all-phased (solid, liquid, and gas) dielectric materials, multidimensional detection-based enhanced accuracy, real-time operation, reusability, and lab-on-a-chip compatibility for microfluidics.…”