WANG RESEARCH GROUP
Microwave Lab-on-Chip
EPR
The schematic of the EPR system (left) with a vector network analyzer (VNA), an RF interferometer (two power dividers (PD), a phase shifter (Ï•), an attenuator (R) and testing device, which can be a microwave resonator (MR) or a meandered-microstrip line (MML)), an electromagnet, and a PC for control.
An experiment setup of the EPR testing system with an RF interferometer and a VNA
Automatic ESR measurements, including sensitivity and frequency tuning
Measuring 0.2 μg 2,2-diphenyl-1-picrylhydrazyl (DPPH) with a microwave resonator (MR)
Measure ESR spectrum of 0.2 μg DPPH with an MR at 7.6 GHz. Signals Δ|S21|min and Δf are absorption and dispersion ESR responses, respectively
Measuring 6 μg 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL) crystal with a broadband meander line (MML)
Measure ESR spectrum of 6 μg DPPH with the MML at 12.3 GHz. Signals Δ|S21|min and Δf are absorption and dispersion ESR responses, respectively.
Multi scan operation
Multi-scan operation can significantly improve ESR signal-to-noise-ratio (SNR).
N = 1
N = 100
N = 200
Absorption and dispersion ESR signals from a 0.2 μg TEMPOL crystal on a meandered microstrip line (MML) with different number of measurements N = 1, 100 and 200.
SNR vs. N
Measured SNR vs. N for both absorption and dispersion signals