Metamaterial inspired periodic structure used for microfluidic sensing

Abstract

A novel metamaterial inspired resonating structure coupled with a microfluidic channel has been evaluated for sensing applications in the microwave frequency range. The structure is based on an open split ring resonator (OSRR) design, was simulated in a finite element analysis tool (Ansys HFSS R ) and tested using a Vector Network Analyzer to detect changes in resonant frequency, amplitude, and phase due to dielectric loading from different chemicals in the microfluidic channel. The sensor was tested as a single unit cell, in a three cell aperiodic array and as an array of three different frequencies. Different concentrations of water-isopropanol (IPA) and watermethanol were used to characterize the sensor. Additionally, a biosensor application was demonstrated in detecting glucose-d concentration in deionized water. BackgroundThere is a growing demand for inexpensive sensors that can effectively detect changes in material properties in extremely small samples of liquids. Applications range from biomedical devices, lab on chip devices, environmental monitoring and forensic investigations. Optical detection is considered the superior technology for use in microfluidic devices given its predominant use and well understood phenomena [1]. The key technologies from the optical perspective are absorbance detection, fluorescence detection, chemiluminescence detection, interferometric detection, and surface plasmon resonance detection. These approaches can be costly, require regular calibration and are limited in their ability to be miniaturized. Many of these approaches also rely on the use of "tagging", where fluorescent markers are used, which compromise the integrity of the chemical sample. Our approach to use a microstrip based microwave structure does not require calibration, does not require tagging, is simple and inexpensive to fabricate, and can easily be miniaturized.Microfluidic sensors in the microwave and radio frequency region have previously been demonstrated. The work described in [2] had a radio frequency device for sensing changes in small liquid samples that was transmission line based, the work in [3][4][5] use spiral based structures and show good sensitivity in the microwave region as well. Our approach requires a much less complicated design than the proposed system in [2] and has a few key advantages over the spiral based structures. Our structure has its electric field relatively concentrated in key areas on the designs surface meaning our microfluidic channel can be much simpler and smaller, thus requiring less fluid to get results. Our structure is also much smaller than the spiral based designs currently proposed and could be fur-

Review of Recent Metamaterial Microfluidic Sensors

“…An open split ring resonator (OSRR) coupled with a microfluidic channel has been proposed as a chemical sensor [ 37 ]. It has been designed on RO3003 substrate (h = 1.52 mm, ε r = 3, tanδ = 0.0013) to operate at 6.5 GHz.…”

“…Most of the metamaterials inspired chemical sensors can detect only one analyte at a time because they use a single channel for sensing. To address this limitation, multichannel per sensor has been developed (e.g., [ 37 , 39 , 41 ]). Metamaterial inspired unit cells were collectively utilized to realize an array [ 37 , 39 ].…”

Multi-Negative Index Band Metamaterial-Inspired Microfluidic Sensors

“…transmission band of at least 50% transmission at −6 dB, observed from S 21 , is generated covering all the X-band range, from 8 GHz to 14 GHz, with two narrow stopbands at 9.62 GHz and 11.36 GHz. These good transmission passbands are proved to have a negative index, the real part, from 8.22 GHz to 16.84 GHz, marked in the refractive index plot in Figure 7(b). The imaginary part of the refractive index, signifying material loss, is low within the operating range.…”

Metafluidic metamaterial: a review

“…In addition, the metamaterial's resonance also differs when covered by chemical solvents with different concentrations. This can be used for both the optical response tuning and the liquid concentration analyzing [56][57][58][59]. For example, a tunable absorber realizes a linear frequency shift from 20% to 80%, which corresponds to an ethanol concentration from 0 to 100% [60].…”