Ultra-high resolution sensing of glucose concentration based on amplified half-integer localized surface plasmons mode

Abstract

Since the half-integer order localized surface plasmons mode is more sensitive to the change of the surrounding materials, an active spoof plasmonic microfluidic sensor using the mode for detecting minute change of glucose aqueous solutions has been proposed at microwave frequencies. By introducing an active coupling circuit near the slit of the spoof plasmonic resonator, the measured quality factor of the half integer order mode (n = 1.5) for the active spoof plasmonic resonator is increased from 148 to 40 000 and the dephasing time is increased to about 16.5 µs when the optimal bias voltage is applied, compared to the passive spoof plasmonic resonator. The resonance frequency changes from 2.45 GHz to 1.74 GHz, with a frequency shift of 710 MHz, when the microfluidic channel is filled with distilled water (about 12 µl). The experiments show that the resonance frequency increases almost linearly with the concentration of the glucose solution. The limit of detection of the active sensor is 9 mg dl −1 . The figure of merit reaches 2236 MHz/(mg/dl). The high-resolution active spoof plasmonic sensor could find more potential applications for biological and chemical sensing.

Millimeter-Wave-Based Spoof Localized Surface Plasmonic Resonator for Sensing Glucose Concentration

“…The former sensors are smaller, can assess smaller sample volumes, have higher sensitivity than the latter, and do not require additional circuit parts. Moreover, conventional spoof SP-or LSP-based sensors have higher sensitivity to permittivity than sensors based on other methods because of the near-field enhancement [32][33][34][35]. 1 Measured value with only the sensor without any additional parts.…”

Flexible and Printed Microwave Plasmonic Sensor for Noninvasive Measurement

“…It has been shown that the Q factor would decrease when the materials under test is high-loss, such as polar solutions [32]. To evaluate the sensitivity of the microwave plasmonic sensors, the figure of merit (FOM) is defined by FOM = Q × ∆f /∆ε, where Q is the quality factor, ∆f is the resonant frequency shift and ∆ε is the change of the relative dielectric constant [36]. Compared with other works in Refs.…”

“…In the last few years, the idea of developing sensors based on microwave detection and microtechnology for biological characterization has been emerging [26]- [27]. The characteristic parameters of the fluids, even very small volumes (lower than few μL), can be accurately determined based on the measured impedance, resonant frequency, insertion loss, or the phase of the microwave or radio frequency (RF) signals [28]- [36], with the advantages of robustness, light weight and durability. However, the sensitivity is still limited.…”

Impacts of Liquid Level on Microwave Resonance Sensing with a Flexible Microfluidic Channel

“…Microfluidic channels are commonly employed to control the inlet and outlet of the solution to build a more controllable environment. [40][41][42][43] Even though, resonance shifts have been reported to present reverse trends varying with the glucose concentration, when the detection limits approach the mg mL −1 level. [9,[44][45][46] These phenomena are inexplicable and indicate that there must be some issues to be addressed to lower any possible signal disturbances or null shifts.…”