Development of LC resonator for label-free biomolecule detection

In this research, LC resonator was designed and tested for biomolecule detection. As the first step, 15 nH spiral inductor at 2 GHz and 15 pF inter-digital capacitor at 2 GHz were designed. And the measured each inductance and capacitance were 15.3 nH and 0.41 pF at 2 GHz. From both the data, LC resonator was designed by the combination of inductor and capacitor. The difference of return loss between bare device after fabrication and biotin binding was 1.87 dB, and biotin–avidin binding was 0.53 dB at 2.2 GHz, respectively. The impedances for bare device, biotin and avidin steps were Zo*(0.718-j0.002), Zo*(0.761-j0.003) and Zo*(0.803-j0.002) in the Smith chart, respectively. From the mentioned data, we can conclude that the return loss variation at resonance point is large distinctly. From the smith chart analysis, we can confirm that the biomolecule acts as a resistance and the increased resistance of the resonator leads to the impedance matching change.